1 00:00:00,030 --> 00:00:02,410 The following content is provided under a creative 2 00:00:02,410 --> 00:00:03,830 commons license. 3 00:00:03,830 --> 00:00:06,860 Your support will help MIT OpenCourseWare continue to 4 00:00:06,860 --> 00:00:10,530 offer high-quality educational resources for free. 5 00:00:10,530 --> 00:00:13,390 To make a donation or view additional materials from 6 00:00:13,390 --> 00:00:17,490 hundreds of MIT courses, visit MIT OpenCourseWare at 7 00:00:17,490 --> 00:00:18,740 ocw.mit.edu. 8 00:00:21,130 --> 00:00:21,450 PROFESSOR: OK. 9 00:00:21,450 --> 00:00:24,040 Couple of announcements. 10 00:00:24,040 --> 00:00:28,130 First of all, the Wolf Lecture is tomorrow, right here in 11 00:00:28,130 --> 00:00:30,930 10-250 at 4:00. 12 00:00:30,930 --> 00:00:34,790 As also, there will be the weekly quiz, the mini 13 00:00:34,790 --> 00:00:36,060 celebration. 14 00:00:36,060 --> 00:00:42,200 But there's going to be, a week from today, celebration 15 00:00:42,200 --> 00:00:44,330 part trois. 16 00:00:44,330 --> 00:00:48,510 Yes, third celebration of learning. 17 00:00:48,510 --> 00:00:50,410 And remember, what we're shooting for 18 00:00:50,410 --> 00:00:53,830 is the smiley face. 19 00:00:53,830 --> 00:00:54,320 None of this. 20 00:00:54,320 --> 00:00:57,000 And those of you who are over here on the grade point 21 00:00:57,000 --> 00:01:00,790 distribution curve, we want to move you to the right. 22 00:01:00,790 --> 00:01:03,300 So I'll say a little bit more later in the week about what 23 00:01:03,300 --> 00:01:06,800 the coverage will be. 24 00:01:06,800 --> 00:01:10,550 I'll be available for office hours later, and 25 00:01:10,550 --> 00:01:14,790 I thought to try to cheer you up, and remind you that 26 00:01:14,790 --> 00:01:16,920 studying is not something you do only the 27 00:01:16,920 --> 00:01:18,960 night before the exam. 28 00:01:18,960 --> 00:01:21,140 You have to be studying on a regular basis. 29 00:01:21,140 --> 00:01:21,910 All right? 30 00:01:21,910 --> 00:01:25,860 So from the iconic film Ghostbusters, 31 00:01:25,860 --> 00:01:27,110 there's this one scene. 32 00:01:29,736 --> 00:01:31,090 [FILM PLAYBACK] 33 00:01:31,090 --> 00:01:35,160 For a moment, pretend that I don't know anything about 34 00:01:35,160 --> 00:01:39,280 metallurgy, engineering, or physics, and just tell me what 35 00:01:39,280 --> 00:01:41,710 the hell is going on. 36 00:01:41,710 --> 00:01:42,960 You never studied. 37 00:01:45,483 --> 00:01:46,960 [END FILM PLAYBACK] 38 00:01:46,960 --> 00:01:51,230 You don't want to be a character in that scene. 39 00:01:51,230 --> 00:01:53,090 So what are you going to do about it? 40 00:01:53,090 --> 00:01:55,040 You're going to study. 41 00:01:55,040 --> 00:01:56,120 All right. 42 00:01:56,120 --> 00:01:57,130 Let's get down to work. 43 00:01:57,130 --> 00:02:01,050 Today I'm going to take one day and I'm going to talk 44 00:02:01,050 --> 00:02:02,250 about organic chemistry. 45 00:02:02,250 --> 00:02:05,090 Now, I'm not going to pretend that after one lecture, you're 46 00:02:05,090 --> 00:02:08,200 going to walk out of here and know much organic chemistry. 47 00:02:08,200 --> 00:02:09,820 I'm going to give you, if you want to know organic 48 00:02:09,820 --> 00:02:11,440 chemistry, you're going to have to take 512, 49 00:02:11,440 --> 00:02:12,750 and many if you will. 50 00:02:12,750 --> 00:02:15,150 But I'm going to give you enough that it will set up for 51 00:02:15,150 --> 00:02:19,480 the subsequent units on polymers and on biochemistry. 52 00:02:19,480 --> 00:02:22,300 So we'll know enough that we can move forward. 53 00:02:22,300 --> 00:02:24,720 So let's get into the 54 00:02:24,720 --> 00:02:26,480 definition of organic chemistry. 55 00:02:26,480 --> 00:02:29,310 It's the chemistry of compounds, containing both 56 00:02:29,310 --> 00:02:31,450 carbon and hydrogen. 57 00:02:31,450 --> 00:02:33,980 There can be, of course, other elements present, but you've 58 00:02:33,980 --> 00:02:35,580 got to have carbon and hydrogen to get 59 00:02:35,580 --> 00:02:38,180 yourself into Orgo. 60 00:02:38,180 --> 00:02:40,460 And what makes carbon and hydrogen so special? 61 00:02:40,460 --> 00:02:43,470 We've been studying these elements through the semester. 62 00:02:43,470 --> 00:02:45,250 But just to be reminded. 63 00:02:45,250 --> 00:02:48,260 First of all, hydrogen is peculiar because it's got the 64 00:02:48,260 --> 00:02:50,210 lowest atomic number. 65 00:02:50,210 --> 00:02:54,850 It's got the lone proton, and a single electron. 66 00:02:54,850 --> 00:02:58,170 And when hydrogen ionizes, it forms the 67 00:02:58,170 --> 00:02:59,930 hydrogen ion, or the proton. 68 00:02:59,930 --> 00:03:00,840 That's all that's left. 69 00:03:00,840 --> 00:03:03,100 And this thing's very tiny, and it can 70 00:03:03,100 --> 00:03:06,400 form covalent bonds. 71 00:03:06,400 --> 00:03:13,680 It forms covalent bonds as primary bonds, and it can form 72 00:03:13,680 --> 00:03:16,890 hydrogen bonds as secondary bonds. 73 00:03:16,890 --> 00:03:20,020 So it's peculiar for that reason. 74 00:03:20,020 --> 00:03:21,840 It does not form ions. 75 00:03:21,840 --> 00:03:25,640 You cannot imagine something is tiny as a proton occupying 76 00:03:25,640 --> 00:03:28,310 a lattice site in an ionic crystal. 77 00:03:28,310 --> 00:03:28,630 OK. 78 00:03:28,630 --> 00:03:31,950 Now when it comes to carbon, carbon is also peculiar. 79 00:03:31,950 --> 00:03:35,470 It's smack dab in the middle of the periodic table, in the 80 00:03:35,470 --> 00:03:36,220 second row. 81 00:03:36,220 --> 00:03:39,370 Four valence electrons, which means that it's very 82 00:03:39,370 --> 00:03:40,930 difficult to ionize. 83 00:03:40,930 --> 00:03:43,270 If it wants to achieve octet stability, it's going to have 84 00:03:43,270 --> 00:03:44,770 to form covalent compounds. 85 00:03:44,770 --> 00:03:47,700 It's not going to acquire four electrons or lose four 86 00:03:47,700 --> 00:03:48,310 electronics. 87 00:03:48,310 --> 00:03:51,620 In rare exceptional circumstances it, might, but 88 00:03:51,620 --> 00:03:53,340 commonly, it does not. 89 00:03:53,340 --> 00:03:56,330 And with that intermediate average valence electron 90 00:03:56,330 --> 00:04:00,040 energy, it's going to be capable of 91 00:04:00,040 --> 00:04:02,050 all sorts of bonding. 92 00:04:02,050 --> 00:04:08,620 And in particular, because of its small size, it's capable, 93 00:04:08,620 --> 00:04:12,110 with its small size and the intermediate value of average 94 00:04:12,110 --> 00:04:13,770 valence electron energy-- 95 00:04:13,770 --> 00:04:15,490 and this is critical-- 96 00:04:15,490 --> 00:04:18,115 is that it's capable of forming multiple bonds. 97 00:04:26,540 --> 00:04:29,630 And this is key, as we'll see later when things try to 98 00:04:29,630 --> 00:04:32,770 polymerize and form multiple bonds. 99 00:04:32,770 --> 00:04:38,690 And this is not common, for example, not the case if you 100 00:04:38,690 --> 00:04:40,920 look underneath carbon. 101 00:04:40,920 --> 00:04:43,410 Silicon, germanium, for example. 102 00:04:43,410 --> 00:04:44,720 Same thing. 103 00:04:44,720 --> 00:04:48,160 Group 4, same kind of mid-stream average valence 104 00:04:48,160 --> 00:04:49,010 electron energy. 105 00:04:49,010 --> 00:04:50,570 But they're too big. 106 00:04:50,570 --> 00:04:54,900 Silicon and Germanium do not form double and triple bonds. 107 00:04:54,900 --> 00:04:57,880 So the other thing is that it's capable of self-linking. 108 00:05:01,210 --> 00:05:06,990 It can link to itself, form carbon chains, and also with 109 00:05:06,990 --> 00:05:09,380 nitrogen, oxygen, sulfur. 110 00:05:09,380 --> 00:05:11,040 So this gives it-- 111 00:05:11,040 --> 00:05:13,490 and let's put up phosphorus as well. 112 00:05:13,490 --> 00:05:14,860 Phosphorus and sulfur. 113 00:05:14,860 --> 00:05:16,740 So with these kinds of links-- we've 114 00:05:16,740 --> 00:05:18,740 already seen oxygen links. 115 00:05:18,740 --> 00:05:21,850 We'll see, pretty soon, nitrogen links and so on. 116 00:05:21,850 --> 00:05:24,960 There's millions of organic compounds, and today I'm just 117 00:05:24,960 --> 00:05:25,690 going to look at a few. 118 00:05:25,690 --> 00:05:27,790 I'm just going to give you some taxonomy and 119 00:05:27,790 --> 00:05:31,510 nomenclature, and we're going to walk through this. 120 00:05:31,510 --> 00:05:33,170 And here's the way to keep it straight. 121 00:05:33,170 --> 00:05:34,440 You know all this stuff. 122 00:05:34,440 --> 00:05:36,720 I'm just going to organize it in your minds for you. 123 00:05:36,720 --> 00:05:39,100 We've already studied the three different types of 124 00:05:39,100 --> 00:05:39,970 hybridization. 125 00:05:39,970 --> 00:05:42,480 sp, sp2, and sp3. 126 00:05:42,480 --> 00:05:44,690 And we've already seen that if you're going to have a double 127 00:05:44,690 --> 00:05:49,100 bond, you need sp2 hybridization to reserve 1p 128 00:05:49,100 --> 00:05:52,330 orbital, to make that pi second bond. 129 00:05:52,330 --> 00:05:55,770 And if you want to make triple bonds, you make sp 130 00:05:55,770 --> 00:05:59,932 hybridization, thereby reserving two p orbitals to 131 00:05:59,932 --> 00:06:01,740 make two pi bonds. 132 00:06:01,740 --> 00:06:06,280 So this is sigma, sigma plus pi, sigma plus pi plus pi. 133 00:06:06,280 --> 00:06:06,920 That's it. 134 00:06:06,920 --> 00:06:10,570 Now what we're going to do is to is go back and look at this 135 00:06:10,570 --> 00:06:13,830 in the context of hydrocarbons. 136 00:06:13,830 --> 00:06:18,520 So hydrocarbons is going to be now the focus here, and the 137 00:06:18,520 --> 00:06:22,860 hydrocarbons are the simplest of the organic compounds. 138 00:06:22,860 --> 00:06:26,640 So let's look at hydrocarbons. 139 00:06:26,640 --> 00:06:29,470 I'm going to look at their nomenclature and their 140 00:06:29,470 --> 00:06:30,150 properties. 141 00:06:30,150 --> 00:06:36,580 But the structure behind everything, the treatment, is 142 00:06:36,580 --> 00:06:38,990 the type of hybridization. 143 00:06:38,990 --> 00:06:42,520 So these consist only of hydrogen and carbon. 144 00:06:42,520 --> 00:06:49,420 Compounds containing only hydrogen and carbon. 145 00:06:49,420 --> 00:06:53,790 So I'm just going to go down that chart. 146 00:06:53,790 --> 00:06:54,620 And we'll go through. 147 00:06:54,620 --> 00:06:59,520 So the first one on the left is the alkanes We'll look at 148 00:06:59,520 --> 00:07:01,290 the alkanes. 149 00:07:01,290 --> 00:07:04,030 And the alkanes are characterized by sp3 150 00:07:04,030 --> 00:07:05,410 hybridization. 151 00:07:05,410 --> 00:07:09,123 And so this gives the maximum number of carbon linkages. 152 00:07:13,390 --> 00:07:13,730 Why? 153 00:07:13,730 --> 00:07:15,570 Because you can only form single bonds. 154 00:07:15,570 --> 00:07:18,960 So if I can only form single bonds, every bond goes to a 155 00:07:18,960 --> 00:07:19,890 different atom. 156 00:07:19,890 --> 00:07:22,260 Whereas if I form double bonds, then I'm burning up 157 00:07:22,260 --> 00:07:23,370 some of the capability. 158 00:07:23,370 --> 00:07:26,030 Because if I used two bonds to get to one neighboring 159 00:07:26,030 --> 00:07:29,740 element, instead of two single bonds each to two different 160 00:07:29,740 --> 00:07:32,440 neighboring elements, I don't have as many linkages. 161 00:07:32,440 --> 00:07:35,630 So the maximum number of carbon linkages-- and because 162 00:07:35,630 --> 00:07:37,980 they have the maximum number, we're going to borrow 163 00:07:37,980 --> 00:07:41,430 terminology from the last unit on solutions. 164 00:07:41,430 --> 00:07:45,310 What's the maximum amount of solute you can get into a 165 00:07:45,310 --> 00:07:46,380 solution called? 166 00:07:46,380 --> 00:07:48,400 It's called the saturation value. 167 00:07:48,400 --> 00:07:49,880 And they use that term here. 168 00:07:49,880 --> 00:07:56,760 These are called saturated hydrocarbons, because they've 169 00:07:56,760 --> 00:08:00,620 got the maximum number of linkages, bonds. 170 00:08:00,620 --> 00:08:04,360 And they're all sigma bonds. 171 00:08:04,360 --> 00:08:07,170 All of this is a consequence of the choice of sp3. 172 00:08:07,170 --> 00:08:10,200 I could have led you through all of this, but we're putting 173 00:08:10,200 --> 00:08:11,750 it up quickly here. 174 00:08:11,750 --> 00:08:12,070 All right. 175 00:08:12,070 --> 00:08:13,940 And so they have a common formula. 176 00:08:13,940 --> 00:08:18,590 CNH2N plus 2. 177 00:08:21,790 --> 00:08:23,350 I think I've got some-- 178 00:08:23,350 --> 00:08:25,970 yeah, this is taking from one of the other books. 179 00:08:25,970 --> 00:08:27,810 I know you've got a list like this in your own book. 180 00:08:27,810 --> 00:08:28,880 So here they are. 181 00:08:28,880 --> 00:08:34,710 So this is just CNH2N plus 2, and you go down, and there's 182 00:08:34,710 --> 00:08:37,560 the nomenclature. 183 00:08:37,560 --> 00:08:41,910 The meth, for historical reasons represents n equals 1. 184 00:08:41,910 --> 00:08:46,110 So here's what the hidden message is. 185 00:08:46,110 --> 00:08:55,470 You name them by the carbon number plus the suffix A N E. 186 00:08:55,470 --> 00:08:59,710 So the -anes, the alk-anes, are all these sp3. 187 00:08:59,710 --> 00:09:05,810 So 1 is meth, 2 is eth, 3 is pro, and 4 is but. 188 00:09:05,810 --> 00:09:09,560 And they all have historical derivations. 189 00:09:09,560 --> 00:09:16,040 But- comes from butyric acid, which is the acid that's 190 00:09:16,040 --> 00:09:18,110 formed when butter turns rancid, and so on. 191 00:09:18,110 --> 00:09:20,640 After you get up to N equals 4, it's just your Latin. 192 00:09:20,640 --> 00:09:23,520 So you just take your high school Latin, pentane, hexane, 193 00:09:23,520 --> 00:09:25,630 heptane, and so on. 194 00:09:25,630 --> 00:09:27,400 And if you didn't take high school Latin, this is a great 195 00:09:27,400 --> 00:09:30,310 chance to learn the ordinals in Latin. 196 00:09:30,310 --> 00:09:31,290 So there they are. 197 00:09:31,290 --> 00:09:33,030 Now, I'm not going to expect you to-- 198 00:09:33,030 --> 00:09:36,880 if I say decane, you're supposed to slam down C10H22. 199 00:09:36,880 --> 00:09:40,480 But I would expect that I could say decane, and I'd give 200 00:09:40,480 --> 00:09:44,100 you that formula and you'd be comfortable with it. 201 00:09:44,100 --> 00:09:47,250 What's the other thing to note here, while we've got this up 202 00:09:47,250 --> 00:09:48,960 on the chart. 203 00:09:48,960 --> 00:09:53,790 You can see that all of these are symmetric molecules, and 204 00:09:53,790 --> 00:09:55,300 they're non-polar. 205 00:09:55,300 --> 00:09:57,550 They're perfectly symmetric non-polar. 206 00:09:57,550 --> 00:10:01,840 And what happens as the molecular mass increases, the 207 00:10:01,840 --> 00:10:05,190 melting point increases, the boiling point increases, and 208 00:10:05,190 --> 00:10:09,050 the state of matter transitions from gas at room 209 00:10:09,050 --> 00:10:11,850 temperature to liquid at room temperature to solid at room 210 00:10:11,850 --> 00:10:12,340 temperature. 211 00:10:12,340 --> 00:10:16,810 So here's an excellent example of polarizability in action. 212 00:10:16,810 --> 00:10:19,590 Because the only way one methane can bond to another 213 00:10:19,590 --> 00:10:24,390 methane is by induced dipole-induced dipole 214 00:10:24,390 --> 00:10:25,520 interaction. 215 00:10:25,520 --> 00:10:29,200 So the only difference between methane and icosane is that 216 00:10:29,200 --> 00:10:33,550 icosane is a honking big molecule, non-polar, but very 217 00:10:33,550 --> 00:10:35,290 polarizable. 218 00:10:35,290 --> 00:10:39,160 And so as the polarizability increases, you can see the 219 00:10:39,160 --> 00:10:40,370 effect here. 220 00:10:40,370 --> 00:10:42,790 OK, so that's good. 221 00:10:42,790 --> 00:10:45,450 So you get to learn your Latin ordinals. 222 00:10:45,450 --> 00:10:50,380 Now these are also termed straight chains. 223 00:10:50,380 --> 00:10:52,980 They can be termed straight chains, but I want you to look 224 00:10:52,980 --> 00:10:56,350 carefully at what's going on here. 225 00:10:56,350 --> 00:10:59,270 So here's a diagram used, the first one on the left, you've 226 00:10:59,270 --> 00:11:01,060 seen methane many times. 227 00:11:01,060 --> 00:11:03,860 There's ethane and then propane. 228 00:11:03,860 --> 00:11:05,120 And what do you notice here? 229 00:11:05,120 --> 00:11:08,050 Because of the sp3 hybridization, all of these 230 00:11:08,050 --> 00:11:10,170 angles are 109 degrees, including the 231 00:11:10,170 --> 00:11:12,100 carbon-carbon angles. 232 00:11:12,100 --> 00:11:15,310 And when the thing is really short, you get 233 00:11:15,310 --> 00:11:16,880 this zig-zaggy nature. 234 00:11:16,880 --> 00:11:21,600 So because of the sp3 hybridization, you see the 235 00:11:21,600 --> 00:11:23,960 carbon doing this. 236 00:11:23,960 --> 00:11:26,490 This is carbon-carbon, and then the rest, forget it. 237 00:11:26,490 --> 00:11:28,110 I mean, this is the backbone. 238 00:11:28,110 --> 00:11:31,300 But if I get up to icosane and I have about 20 of these 239 00:11:31,300 --> 00:11:33,750 things, forget the zig-zag. 240 00:11:33,750 --> 00:11:36,050 From here, yeah, I know there's a little bit of fine 241 00:11:36,050 --> 00:11:39,990 structure, but for all intents and purposes, this as a chain. 242 00:11:39,990 --> 00:11:41,390 Straight chain. 243 00:11:41,390 --> 00:11:43,090 And that's where you get the terminology from. 244 00:11:43,090 --> 00:11:46,490 But keep in mind that there is this zig-zagging back and 245 00:11:46,490 --> 00:11:49,750 forth, due to the sp3 hybridization. 246 00:11:49,750 --> 00:11:50,690 OK? 247 00:11:50,690 --> 00:11:52,550 So that's the first point. 248 00:11:52,550 --> 00:11:57,930 The second point is that the bonds between the carbons are 249 00:11:57,930 --> 00:11:59,300 not fully specified. 250 00:11:59,300 --> 00:12:02,560 So for example, take the carbon here on the left. 251 00:12:02,560 --> 00:12:06,070 The sticks to go to the 3 hydrogens here depicted in 252 00:12:06,070 --> 00:12:09,400 white, and then the fourth stick goes to the carbon. 253 00:12:09,400 --> 00:12:12,370 And then off of that carbon comes 3 more sticks, and all 254 00:12:12,370 --> 00:12:14,520 of these are 109 degree angles. 255 00:12:14,520 --> 00:12:17,340 All of that specified, and nothing more. 256 00:12:17,340 --> 00:12:20,750 There's nothing saying that these 2 hydrogens in the back 257 00:12:20,750 --> 00:12:21,740 have to line up. 258 00:12:21,740 --> 00:12:24,890 These two hydrogens out front have to the line up. 259 00:12:24,890 --> 00:12:27,270 That's all free to rotate. 260 00:12:27,270 --> 00:12:30,310 And so we have that degree of freedom there. 261 00:12:30,310 --> 00:12:33,800 The result is that you can have something that zig-zags 262 00:12:33,800 --> 00:12:34,570 back and forth. 263 00:12:34,570 --> 00:12:37,860 So for example, this is called eclipse, because if I were to 264 00:12:37,860 --> 00:12:40,340 stand here, these two hydrogens 265 00:12:40,340 --> 00:12:41,790 are on a direct line. 266 00:12:41,790 --> 00:12:44,910 So the front hydrogen covers the back hydrogen. 267 00:12:44,910 --> 00:12:46,080 It eclipses. 268 00:12:46,080 --> 00:12:54,210 This hydrogen out front to your and my right is on the 269 00:12:54,210 --> 00:12:57,420 same line is this hydrogen to your and my left. 270 00:12:57,420 --> 00:13:00,110 And so if I were to look here from the end, this hydrogen 271 00:13:00,110 --> 00:13:01,930 eclipses, and so on. 272 00:13:01,930 --> 00:13:04,820 So if I get something eclipsed, I'm going to have a 273 00:13:04,820 --> 00:13:06,290 perfect straight line. 274 00:13:06,290 --> 00:13:09,530 If I have something that's staggered, it's free to 275 00:13:09,530 --> 00:13:12,560 zig-zag, but it's free to zig-zag and meander, and this 276 00:13:12,560 --> 00:13:13,270 is what happens. 277 00:13:13,270 --> 00:13:20,650 So here's 2 C17H36 molecules, and the top confirmation is 278 00:13:20,650 --> 00:13:22,310 more or less straight. 279 00:13:22,310 --> 00:13:27,170 These are more or less eclipsed configurations. 280 00:13:27,170 --> 00:13:29,560 Whereas the lower one, you can see, there's a fair bit of 281 00:13:29,560 --> 00:13:33,640 stagger, and as a result, the backbone can actually loop 282 00:13:33,640 --> 00:13:34,860 back on itself. 283 00:13:34,860 --> 00:13:38,670 But in both cases, we still call these straight chains. 284 00:13:38,670 --> 00:13:39,840 They're still straight chain. 285 00:13:39,840 --> 00:13:43,340 Because as you start at one end and go from carbon to 286 00:13:43,340 --> 00:13:46,580 carbon, you linearly go to the other end. 287 00:13:46,580 --> 00:13:49,450 It doesn't mean it's straight like straight as an arrow. 288 00:13:49,450 --> 00:13:52,550 It just means there's no branches. 289 00:13:52,550 --> 00:13:54,430 So now I'm going to distinguish this from the 290 00:13:54,430 --> 00:13:56,940 other one by branching. 291 00:13:56,940 --> 00:13:58,910 So let's just get this up here. 292 00:13:58,910 --> 00:14:03,300 So we have straight chains, is one case. 293 00:14:03,300 --> 00:14:04,330 Straight chains. 294 00:14:04,330 --> 00:14:06,580 And the straight chains can either be 295 00:14:06,580 --> 00:14:10,945 staggered or eclipsed. 296 00:14:13,510 --> 00:14:16,470 And the closer you get to eclipsed, the 297 00:14:16,470 --> 00:14:17,720 closer you get to-- 298 00:14:21,410 --> 00:14:23,400 the more eclipsed, the straighter. 299 00:14:23,400 --> 00:14:25,600 I think you'll understand what this means. 300 00:14:25,600 --> 00:14:29,930 Staggered allows it to make large loops-- 301 00:14:29,930 --> 00:14:34,670 I'll just put here, straight but looped. 302 00:14:34,670 --> 00:14:37,420 You can use that to describe some of your friends, too. 303 00:14:37,420 --> 00:14:37,820 All right. 304 00:14:37,820 --> 00:14:38,850 Now-- 305 00:14:38,850 --> 00:14:40,780 it's a Monday, it's a joke! 306 00:14:40,780 --> 00:14:42,120 Wake up! 307 00:14:42,120 --> 00:14:43,660 Wake up! 308 00:14:43,660 --> 00:14:44,070 All right. 309 00:14:44,070 --> 00:14:45,500 Now we can look at another one. 310 00:14:45,500 --> 00:14:46,750 Branched chains. 311 00:14:49,590 --> 00:14:53,840 And now, this will be a major departure, whether the chain 312 00:14:53,840 --> 00:14:58,490 is super-straight or does a lot of looping back and forth, 313 00:14:58,490 --> 00:15:00,900 the branched chain is in marked contrast. Now let me 314 00:15:00,900 --> 00:15:03,720 give you an example of the branch chain. 315 00:15:03,720 --> 00:15:05,130 Best to just do it. 316 00:15:05,130 --> 00:15:07,210 So here's the branch chain. 317 00:15:07,210 --> 00:15:10,640 I'm going to use a butane. 318 00:15:10,640 --> 00:15:14,340 So you know B U T is 4. 319 00:15:14,340 --> 00:15:19,220 So that means 4 carbons, and A means 4 carbons, sp3 320 00:15:19,220 --> 00:15:20,170 hybridized. 321 00:15:20,170 --> 00:15:21,040 So that's it. 322 00:15:21,040 --> 00:15:22,120 So now I'm going to write this. 323 00:15:22,120 --> 00:15:22,920 Here's butane. 324 00:15:22,920 --> 00:15:25,840 C, C, C, C. 325 00:15:25,840 --> 00:15:29,770 And I'm going to write this as just a straight chain, instead 326 00:15:29,770 --> 00:15:31,250 of doing this. 327 00:15:31,250 --> 00:15:35,040 I'm going to contrast. I'm going to do 1, 2, 3, 4. 328 00:15:35,040 --> 00:15:37,850 1, 2, 3, 4. 329 00:15:37,850 --> 00:15:39,780 1, 2, 3, 4. 330 00:15:39,780 --> 00:15:42,830 1, 2, 3, 4. 331 00:15:42,830 --> 00:15:43,760 OK? 332 00:15:43,760 --> 00:15:44,400 So there we are. 333 00:15:44,400 --> 00:15:47,000 So this is, instead of writing all this stuff, this is 334 00:15:47,000 --> 00:15:49,270 butane, and this is butane. 335 00:15:49,270 --> 00:15:50,340 But now here's the thing. 336 00:15:50,340 --> 00:15:51,590 Four stick rule. 337 00:15:55,370 --> 00:15:57,910 Whenever you're doing Orgo, four stick rule. 338 00:15:57,910 --> 00:16:00,580 That means, four sticks out of every carbon. 339 00:16:00,580 --> 00:16:02,820 So here's the carbon-carbon bond, so I 340 00:16:02,820 --> 00:16:04,040 need three more sticks. 341 00:16:04,040 --> 00:16:05,040 1, 2, 3. 342 00:16:05,040 --> 00:16:08,140 And I know these are sp3 hybridized, but just, in 343 00:16:08,140 --> 00:16:10,240 compressed notation, you can do this. 344 00:16:10,240 --> 00:16:13,490 And I'm not even going to write all the hydrogens. 345 00:16:13,490 --> 00:16:17,180 Here I'm going to write the hydrogens because it's our 346 00:16:17,180 --> 00:16:19,580 first time through, and it's Monday, and everybody needs a 347 00:16:19,580 --> 00:16:22,420 little bit of TLC. 348 00:16:22,420 --> 00:16:24,390 But now the TLC is gone. 349 00:16:24,390 --> 00:16:25,470 This is it, all right? 350 00:16:25,470 --> 00:16:27,270 I'm not even going to put the H's on the end. 351 00:16:27,270 --> 00:16:30,380 The stick coming off of carbon means there's a hydrogen here. 352 00:16:30,380 --> 00:16:30,860 All right? 353 00:16:30,860 --> 00:16:31,680 So how about this one? 354 00:16:31,680 --> 00:16:36,670 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4. 355 00:16:36,670 --> 00:16:38,090 And now let's count the hydrogens. 356 00:16:38,090 --> 00:16:41,910 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. 357 00:16:41,910 --> 00:16:44,120 C4H10. 358 00:16:44,120 --> 00:16:45,580 Butane. 359 00:16:45,580 --> 00:16:46,090 All right. 360 00:16:46,090 --> 00:16:50,040 Now there's another way to write this. 361 00:16:50,040 --> 00:16:51,700 I could go like so. 362 00:16:51,700 --> 00:16:54,230 1, 2, 3. 363 00:16:54,230 --> 00:16:57,990 And I could put a carbon up here. 364 00:16:57,990 --> 00:16:59,100 This is a branch, you see? 365 00:16:59,100 --> 00:17:00,530 It's not in a straight line. 366 00:17:00,530 --> 00:17:03,930 And I'm not talking about eclipsed. 367 00:17:03,930 --> 00:17:06,590 Because if I start at 1n and go down the backbone, I get to 368 00:17:06,590 --> 00:17:07,860 the other end, I only hit three. 369 00:17:07,860 --> 00:17:09,950 I never got to this one. 370 00:17:09,950 --> 00:17:10,640 But let's see. 371 00:17:10,640 --> 00:17:11,900 You know, maybe this is different. 372 00:17:11,900 --> 00:17:13,520 So four stick rule. 373 00:17:13,520 --> 00:17:15,500 1, 2, 3, 4. 374 00:17:15,500 --> 00:17:17,620 1, 2, 3, 4. 375 00:17:17,620 --> 00:17:19,990 1, 2, 3, 4. 376 00:17:19,990 --> 00:17:21,700 1, 2, 3, 4. 377 00:17:21,700 --> 00:17:23,050 Now let's count the hydrogens. 378 00:17:23,050 --> 00:17:27,360 1, 2, 3, 4, 4, 6, 7, 8, 9, 10. 379 00:17:27,360 --> 00:17:30,730 This is C4H10. 380 00:17:30,730 --> 00:17:33,790 It's a different molecule, you can see. 381 00:17:33,790 --> 00:17:36,450 With what you've already learned in 3091, this has a 382 00:17:36,450 --> 00:17:38,980 different dipole moment, doesn't it? 383 00:17:38,980 --> 00:17:40,190 It's got a different dipole moment. 384 00:17:40,190 --> 00:17:42,660 It's going to have a different polarizability. 385 00:17:42,660 --> 00:17:45,450 But it's a butane, it's a C4H10. 386 00:17:45,450 --> 00:17:48,780 So this is called butane, right? 387 00:17:48,780 --> 00:17:49,740 And this one, over here, 388 00:17:49,740 --> 00:17:51,580 historically, was called isobutane. 389 00:17:55,610 --> 00:17:59,500 Because it's an isomer. 390 00:17:59,500 --> 00:18:06,830 It's got the same chemical composition, but it's got a 391 00:18:06,830 --> 00:18:08,840 different makeup. 392 00:18:08,840 --> 00:18:10,950 It's got a different structural makeup. 393 00:18:10,950 --> 00:18:13,820 It's got a different-- 394 00:18:13,820 --> 00:18:17,500 I'm going to use the material science-y word. 395 00:18:17,500 --> 00:18:19,320 Different structure. 396 00:18:19,320 --> 00:18:21,180 It's got a different molecular structure. 397 00:18:24,500 --> 00:18:27,780 But the chemists going back 50 years ago didn't use these 398 00:18:27,780 --> 00:18:30,920 terms. They called it different constituents. 399 00:18:30,920 --> 00:18:32,390 So I'm going to use that as well. 400 00:18:32,390 --> 00:18:35,786 Different molecular structure or different constituents. 401 00:18:38,970 --> 00:18:41,740 And what do we mean by constituents? 402 00:18:41,740 --> 00:18:43,160 Now comes the color chalk. 403 00:18:43,160 --> 00:18:45,500 So we're going to do, is I want to circle 404 00:18:45,500 --> 00:18:46,400 the makeup of this. 405 00:18:46,400 --> 00:18:49,100 So at this end, I've got-- 406 00:18:49,100 --> 00:18:52,150 this is a CH3 here, correct? 407 00:18:52,150 --> 00:18:56,040 There's a CH3 over here. 408 00:18:56,040 --> 00:19:02,420 And then in between, I've got CH2 and a CH2. 409 00:19:02,420 --> 00:19:05,520 Now let's go over here and diagram this one. 410 00:19:05,520 --> 00:19:11,380 The isobutane, I've got a CH3 at the end, and a CH3 at the 411 00:19:11,380 --> 00:19:12,100 opposite end. 412 00:19:12,100 --> 00:19:14,290 So far, same as the butane. 413 00:19:14,290 --> 00:19:15,290 But now look. 414 00:19:15,290 --> 00:19:20,320 There's a third CH3 here, and then there's this 415 00:19:20,320 --> 00:19:22,960 thing, which is a CH. 416 00:19:22,960 --> 00:19:24,750 You could argue it's a CH2 that got 417 00:19:24,750 --> 00:19:26,140 methylated, but, you know. 418 00:19:26,140 --> 00:19:31,780 So I'm going to put a CH2 here that's been methylated. 419 00:19:31,780 --> 00:19:33,970 And I'll tell you what that means. 420 00:19:33,970 --> 00:19:34,370 OK? 421 00:19:34,370 --> 00:19:37,910 So it's really a CH2 group that got methylated. 422 00:19:37,910 --> 00:19:42,900 So it's called isobutane, but you can see, it's got 423 00:19:42,900 --> 00:19:43,320 different-- 424 00:19:43,320 --> 00:19:46,420 all I'm doing here is making the justification for the 425 00:19:46,420 --> 00:19:48,500 different constitution, different dielectric 426 00:19:48,500 --> 00:19:52,460 constants, and so on and so forth. 427 00:19:52,460 --> 00:19:54,460 So this is where the chemists must come in. 428 00:19:54,460 --> 00:19:56,870 They would say, different constituents. 429 00:19:56,870 --> 00:19:59,490 And so these are isomers that have the same chemical 430 00:19:59,490 --> 00:20:02,070 composition, and are different on the basis of their 431 00:20:02,070 --> 00:20:03,620 constitution. 432 00:20:03,620 --> 00:20:05,820 So they call these constitutional isomers. 433 00:20:09,880 --> 00:20:11,310 This is a constitutional isomer. 434 00:20:11,310 --> 00:20:13,570 Isobutane is a constitutional isomer. 435 00:20:13,570 --> 00:20:16,240 Now the last piece is nomenclature. 436 00:20:16,240 --> 00:20:18,700 They don't use this today. 437 00:20:18,700 --> 00:20:21,080 Because isobutane was a term that came 438 00:20:21,080 --> 00:20:22,510 out of chemical industry. 439 00:20:22,510 --> 00:20:24,440 Because it looks like butane, has got the same molecular 440 00:20:24,440 --> 00:20:26,040 weight, but it's very different. 441 00:20:26,040 --> 00:20:28,010 Today we use the IUPAC notation. 442 00:20:28,010 --> 00:20:28,480 Remember this? 443 00:20:28,480 --> 00:20:31,260 International Union of Pure and Applied Chemistry. 444 00:20:31,260 --> 00:20:33,850 They're the ones, when one of you discovers and stabilizes 445 00:20:33,850 --> 00:20:37,530 element 113, And you want to name it after dadadadada, you 446 00:20:37,530 --> 00:20:40,000 have to get past the IUPAC committee. 447 00:20:40,000 --> 00:20:40,360 OK? 448 00:20:40,360 --> 00:20:44,570 So their nomenclature committee would say, this is 449 00:20:44,570 --> 00:20:48,460 an alkane, but it's only three carbon units long. 450 00:20:48,460 --> 00:20:50,000 So it is not a butane. 451 00:20:50,000 --> 00:20:51,920 It is a propane. 452 00:20:51,920 --> 00:20:53,230 It is a type of propane. 453 00:20:53,230 --> 00:20:55,720 But it's not simple propane, because there's a methyl 454 00:20:55,720 --> 00:20:57,130 hanging off the side. 455 00:20:57,130 --> 00:21:03,750 So in point of fact, this, in IUPAC nomenclature, is a 456 00:21:03,750 --> 00:21:05,830 methyl propane. 457 00:21:05,830 --> 00:21:09,010 And furthermore, if you want to get really pedantic, and 458 00:21:09,010 --> 00:21:12,100 IUPAC loves to get pedantic, is what they'll do, is they'll 459 00:21:12,100 --> 00:21:14,050 number these, starting from left to right. 460 00:21:14,050 --> 00:21:17,150 So this is the number 1 carbon, this is the number 2 461 00:21:17,150 --> 00:21:19,540 carbon, and this is number 3 carbon. 462 00:21:19,540 --> 00:21:22,450 And the methyl group is pendent on 463 00:21:22,450 --> 00:21:23,840 the number 2 carbon. 464 00:21:23,840 --> 00:21:26,950 So if we want to get really, really, really pedantic, and 465 00:21:26,950 --> 00:21:31,090 who wouldn't, on a Monday morning, what we would do, is 466 00:21:31,090 --> 00:21:32,475 we would call this 2-methylpropane. 467 00:21:36,580 --> 00:21:39,390 So it's a propane, 3 carbon units, there's a methyl group 468 00:21:39,390 --> 00:21:40,550 hanging off of number 2. 469 00:21:40,550 --> 00:21:43,510 Now, I don't expect you to be able to do these on sight, but 470 00:21:43,510 --> 00:21:46,510 I would like you to be appreciative of what this is. 471 00:21:46,510 --> 00:21:50,130 So I'll give it to you on an exam. 472 00:21:50,130 --> 00:21:50,390 All right. 473 00:21:50,390 --> 00:21:52,550 So we've got the isomers. 474 00:21:52,550 --> 00:21:54,290 And I think I've got some-- 475 00:21:54,290 --> 00:21:54,990 I think I've got this. 476 00:21:54,990 --> 00:21:55,690 No. 477 00:21:55,690 --> 00:21:58,500 OK, this is good. 478 00:21:58,500 --> 00:21:58,640 Oh. 479 00:21:58,640 --> 00:22:01,030 There's one other thing I want to talk about with alkanes. 480 00:22:01,030 --> 00:22:04,350 There's another thing that we need to know, and that's about 481 00:22:04,350 --> 00:22:05,290 the radicals. 482 00:22:05,290 --> 00:22:06,750 The radicals that form. 483 00:22:06,750 --> 00:22:08,610 The radical is a species with one or 484 00:22:08,610 --> 00:22:11,860 more unpaired electrons. 485 00:22:11,860 --> 00:22:13,110 Right? 486 00:22:22,290 --> 00:22:24,130 This is broken bond. 487 00:22:24,130 --> 00:22:25,220 One pair electrons. 488 00:22:25,220 --> 00:22:30,310 That's equivalent to broken bond. 489 00:22:30,310 --> 00:22:30,910 OK. 490 00:22:30,910 --> 00:22:32,260 So this is highly reactive. 491 00:22:32,260 --> 00:22:34,170 Because this unpaired electron is going to 492 00:22:34,170 --> 00:22:36,800 go look for a mate. 493 00:22:36,800 --> 00:22:38,540 So if you take a look at CH4-- 494 00:22:42,270 --> 00:22:44,170 now I'm going to put the hydrogens in. 495 00:22:44,170 --> 00:22:48,010 So this is methane, CH4. 496 00:22:48,010 --> 00:22:52,000 I'm going to break this bond in the lower right corner, and 497 00:22:52,000 --> 00:22:55,150 just have an unpaired electron. 498 00:22:55,150 --> 00:22:57,290 And this is called the methyl radical. 499 00:23:00,860 --> 00:23:01,730 Very reactive. 500 00:23:01,730 --> 00:23:04,800 So you can see that this methyl radical could go up and 501 00:23:04,800 --> 00:23:08,570 stick on to the fourth strut of that number 2 carbon, and 502 00:23:08,570 --> 00:23:10,350 thereby form the carbon-carbon bond. 503 00:23:10,350 --> 00:23:12,600 So that's why they call this methylpropane. 504 00:23:12,600 --> 00:23:13,950 So the methyl radical. 505 00:23:13,950 --> 00:23:19,160 And you can write it this way, H3C with dot indicating 506 00:23:19,160 --> 00:23:20,450 unpaired electrons. 507 00:23:20,450 --> 00:23:23,750 But I want you to be literate with the way chemists will 508 00:23:23,750 --> 00:23:27,230 write this in various compact notations. 509 00:23:27,230 --> 00:23:32,120 So you might even see it written this way. 510 00:23:32,120 --> 00:23:33,850 Now, that doesn't mean that the unpaired 511 00:23:33,850 --> 00:23:35,380 electron is on a hydrogen. 512 00:23:35,380 --> 00:23:39,990 This is just a way of saying, you know, CH4 is methane, CH3 513 00:23:39,990 --> 00:23:42,760 is methyl, and who cares. 514 00:23:42,760 --> 00:23:44,630 There's only one possible meaning to 515 00:23:44,630 --> 00:23:46,515 this, so it's all good. 516 00:23:46,515 --> 00:23:47,470 All right? 517 00:23:47,470 --> 00:23:49,600 Let's do two unpaired electrons. 518 00:23:49,600 --> 00:23:51,600 So I'm going to take two unpaired electrons. 519 00:23:51,600 --> 00:23:55,180 Again, this is out of the alkane, so I'll put a hydrogen 520 00:23:55,180 --> 00:23:56,200 above and below. 521 00:23:56,200 --> 00:23:58,390 So that would be like this one here. 522 00:23:58,390 --> 00:24:00,080 You see the CH2? 523 00:24:00,080 --> 00:24:03,423 So it's got carbon-carbon bonds on either side, but in 524 00:24:03,423 --> 00:24:05,490 point of fact, this is part of a zig-zag. 525 00:24:05,490 --> 00:24:10,395 So I'm going to break bonds here and here. 526 00:24:10,395 --> 00:24:11,180 All right? 527 00:24:11,180 --> 00:24:13,370 So now I've got the possibility of putting a bond 528 00:24:13,370 --> 00:24:14,610 on either side. 529 00:24:14,610 --> 00:24:18,410 And this one here is called methylene. 530 00:24:18,410 --> 00:24:20,350 This is methylene. 531 00:24:20,350 --> 00:24:22,300 This is the methylene radical, and it's got 532 00:24:22,300 --> 00:24:23,430 two unpaired electrons. 533 00:24:23,430 --> 00:24:30,620 So we could write that as H2C with 2 unpaired electrons. 534 00:24:30,620 --> 00:24:32,500 And, you know, these are electrons. 535 00:24:32,500 --> 00:24:34,090 They're not just anywhere. 536 00:24:34,090 --> 00:24:37,560 They're sitting in an orbital, and that orbital is as at 109 537 00:24:37,560 --> 00:24:40,020 degrees from the other bond. 538 00:24:40,020 --> 00:24:43,250 So it has to be sitting there in reserve, in waiting. 539 00:24:43,250 --> 00:24:46,370 So if I bring another carbon here, I get the carbon-carbon 540 00:24:46,370 --> 00:24:48,860 bond, and I start forming the zig-zag. 541 00:24:48,860 --> 00:24:53,220 And there's one more, a common one that we'll need to know. 542 00:24:53,220 --> 00:24:59,770 And that's from ethane, which is C2H6, right? 543 00:24:59,770 --> 00:25:04,480 Let's start with ethane, C2H6, and I'm going to make a 544 00:25:04,480 --> 00:25:05,283 radical out of that. 545 00:25:05,283 --> 00:25:08,240 It will be C2H5, like this. 546 00:25:08,240 --> 00:25:11,780 To which I can add a hydroxyl, and now I'll make ethyl 547 00:25:11,780 --> 00:25:14,050 alcohol, and then it's party time. 548 00:25:14,050 --> 00:25:15,400 But so this is how you start. 549 00:25:15,400 --> 00:25:16,510 All right? 550 00:25:16,510 --> 00:25:19,130 This is the ethyl radical. 551 00:25:22,520 --> 00:25:24,070 Starting from methane. 552 00:25:24,070 --> 00:25:25,100 And that's pretty much it. 553 00:25:25,100 --> 00:25:27,520 That's about all I want you to really take 554 00:25:27,520 --> 00:25:29,460 away with the alkanes. 555 00:25:32,230 --> 00:25:34,190 C4H10. 556 00:25:34,190 --> 00:25:34,770 Yeah, there you go. 557 00:25:34,770 --> 00:25:37,960 So there you can see, to the left, the zig-zagging of the 558 00:25:37,960 --> 00:25:41,430 linear and the butane, and then the methyl propane. 559 00:25:41,430 --> 00:25:42,050 That's good. 560 00:25:42,050 --> 00:25:42,330 OK. 561 00:25:42,330 --> 00:25:44,190 Now let's go to sp2. 562 00:25:44,190 --> 00:25:46,420 Now we're going to look at the alkenes. 563 00:25:46,420 --> 00:25:49,340 So alkenes represent-- 564 00:25:49,340 --> 00:25:50,830 the alkenes-- 565 00:25:50,830 --> 00:25:54,140 this is sp2 hybridization. 566 00:25:54,140 --> 00:25:56,430 And they contain-- 567 00:25:56,430 --> 00:25:59,010 this means there's the possibility of a carbon-carbon 568 00:25:59,010 --> 00:26:00,690 double bond. 569 00:26:00,690 --> 00:26:05,160 And they're also known as unsaturated. 570 00:26:05,160 --> 00:26:07,390 Because they don't optimize. 571 00:26:07,390 --> 00:26:11,560 The fact that you spent two of your bonds going between two 572 00:26:11,560 --> 00:26:14,490 atoms instead of taking one bond to one carbon and another 573 00:26:14,490 --> 00:26:17,950 bond somewhere else, means that you're undermaximized. 574 00:26:17,950 --> 00:26:22,160 So unsaturated hydrocarbons. 575 00:26:22,160 --> 00:26:22,520 OK? 576 00:26:22,520 --> 00:26:29,030 And the formula for these is CNH2N, where obviously N is 577 00:26:29,030 --> 00:26:29,930 greater than 1. 578 00:26:29,930 --> 00:26:31,970 We can't form a carbon-carton double bond 579 00:26:31,970 --> 00:26:33,050 with only one carbon. 580 00:26:33,050 --> 00:26:36,020 So you know, the prototypical one we looked at was this one 581 00:26:36,020 --> 00:26:38,720 here, just to C2. 582 00:26:38,720 --> 00:26:39,560 That's the first one. 583 00:26:39,560 --> 00:26:41,420 So it's going to be C2H4. 584 00:26:41,420 --> 00:26:42,980 So carbon-carbon double bond. 585 00:26:42,980 --> 00:26:46,180 There's a sigma bond here, and a pi bond. 586 00:26:46,180 --> 00:26:48,230 And they lie in a plane. 587 00:26:48,230 --> 00:26:49,700 The molecule is planar. 588 00:26:49,700 --> 00:26:51,850 120 degrees here. 589 00:26:51,850 --> 00:26:53,530 So we'll put the hydrogens on it-- 590 00:26:53,530 --> 00:26:55,760 you know already, I don't have to put the hydrogens there. 591 00:26:55,760 --> 00:26:56,910 That's good enough. 592 00:26:56,910 --> 00:26:57,240 All right. 593 00:26:57,240 --> 00:26:59,300 So what's this one called? 594 00:26:59,300 --> 00:27:02,240 This is called ethylene, historically. 595 00:27:02,240 --> 00:27:04,100 Ethylene. 596 00:27:04,100 --> 00:27:07,410 But the IUPAC notation is similar to this one. 597 00:27:07,410 --> 00:27:11,070 It's carbon number plus -ene, E N E. 598 00:27:11,070 --> 00:27:14,070 So strictly speaking, this is what everybody knows. 599 00:27:14,070 --> 00:27:16,640 But IUPAC insists-- 600 00:27:16,640 --> 00:27:17,660 and I don't know. 601 00:27:17,660 --> 00:27:21,370 As you publish, some editors are really fastidious, and 602 00:27:21,370 --> 00:27:23,720 they'll force you to change if you use this kind of 603 00:27:23,720 --> 00:27:24,660 terminology. 604 00:27:24,660 --> 00:27:27,350 So you're going to have to call it ethene. 605 00:27:27,350 --> 00:27:30,310 Or in the UK they call it ethene. 606 00:27:30,310 --> 00:27:32,170 But everybody knows it is ethylene. 607 00:27:32,170 --> 00:27:32,460 OK. 608 00:27:32,460 --> 00:27:34,370 So there it is. 609 00:27:34,370 --> 00:27:37,755 And you only need 1 carbon-carbon bond. 610 00:27:37,755 --> 00:27:41,580 So you can have long chains where the 611 00:27:41,580 --> 00:27:43,090 position isn't fixed. 612 00:27:43,090 --> 00:27:46,440 So let's look at a couple of examples. 613 00:27:46,440 --> 00:27:48,500 So let's look at butene. 614 00:27:48,500 --> 00:27:50,260 OK, let me just write that down. 615 00:27:50,260 --> 00:27:50,960 That's good. 616 00:27:50,960 --> 00:28:00,410 The position of carbon-carbon is not fixed. 617 00:28:00,410 --> 00:28:04,220 It just has to be somewhere in the molecule, which consists 618 00:28:04,220 --> 00:28:05,560 only of hydrogen and carbon 619 00:28:05,560 --> 00:28:07,500 So here's a couple of examples. 620 00:28:07,500 --> 00:28:08,390 I'll start with this one. 621 00:28:08,390 --> 00:28:09,640 This is going to be-- 622 00:28:11,630 --> 00:28:16,670 so this is 1, 2, 3, 4, so that's a but- something. 623 00:28:16,670 --> 00:28:19,610 And it's got a double bond, so that's a butene. 624 00:28:19,610 --> 00:28:20,810 It's all hydrocarbon. 625 00:28:20,810 --> 00:28:22,670 So that's butene here. 626 00:28:22,670 --> 00:28:24,930 But I could also-- well, let's finish this. 627 00:28:24,930 --> 00:28:25,300 How many? 628 00:28:25,300 --> 00:28:28,500 This is 1, 2, 3, 4. 629 00:28:28,500 --> 00:28:32,680 See, I even tried to indicate the 120 degrees here. 630 00:28:32,680 --> 00:28:36,190 This is going to be 1, 2, 3, 4. 631 00:28:36,190 --> 00:28:39,260 1, 2, 3, 4, 1, 2, 3, 4. 632 00:28:39,260 --> 00:28:39,990 All right. 633 00:28:39,990 --> 00:28:41,350 So there's the butene. 634 00:28:41,350 --> 00:28:44,570 But there's another place I could put the carbon-carbon 635 00:28:44,570 --> 00:28:45,140 double bond. 636 00:28:45,140 --> 00:28:46,500 I could do it this way. 637 00:28:46,500 --> 00:28:48,910 Make a carbon-carbon single bond, move the carbon-carbon 638 00:28:48,910 --> 00:28:51,820 double bond over to the number 2 position. 639 00:28:51,820 --> 00:28:55,390 this is 1, 2, 3, 4. 640 00:28:55,390 --> 00:28:58,180 So this is going to be 1-butene, and this one here is 641 00:28:58,180 --> 00:29:00,420 going to be 1, 2. 642 00:29:00,420 --> 00:29:02,010 So we'll make this 2-butene. 643 00:29:05,260 --> 00:29:06,370 And let's keep counting here. 644 00:29:06,370 --> 00:29:13,640 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4. 645 00:29:13,640 --> 00:29:15,460 And I've proven to you, I hope, by now that I 646 00:29:15,460 --> 00:29:16,650 can count to four. 647 00:29:16,650 --> 00:29:19,620 So this is 2-butene, right? 648 00:29:19,620 --> 00:29:20,540 2-butene. 649 00:29:20,540 --> 00:29:23,500 And if you go through this using the same kind of 650 00:29:23,500 --> 00:29:26,800 diagrammatic analysis as over here, you're going to come to 651 00:29:26,800 --> 00:29:29,770 the conclusion that even though these both have the 652 00:29:29,770 --> 00:29:35,880 same composition, which is going to be C4H8, they're both 653 00:29:35,880 --> 00:29:41,620 C4H8, but as you diagram them, you'll find that they have 654 00:29:41,620 --> 00:29:42,750 different constituents. 655 00:29:42,750 --> 00:29:45,730 So these, in fact, are constitutional 656 00:29:45,730 --> 00:29:47,700 isomers of one another. 657 00:29:47,700 --> 00:29:51,200 Constitutional isomers. 658 00:29:54,840 --> 00:29:57,320 Yeah, that's pretty good. 659 00:29:57,320 --> 00:29:58,730 There's even more. 660 00:29:58,730 --> 00:30:00,150 It gets even better. 661 00:30:00,150 --> 00:30:05,070 I want to focus on the bottom one, the 2-butene, and I want 662 00:30:05,070 --> 00:30:08,170 to write it out with a little bit more detail. 663 00:30:08,170 --> 00:30:13,450 So let's start with that carbon-carbon double bond. 664 00:30:13,450 --> 00:30:17,410 And we know the carbon-carbon double bond requires planar 665 00:30:17,410 --> 00:30:20,580 structures at 120 degrees from one another. 666 00:30:20,580 --> 00:30:22,080 So let's look at that one. 667 00:30:22,080 --> 00:30:25,220 And what we've got here, is on the carbon, I've got on the 668 00:30:25,220 --> 00:30:27,880 one side, I've got a hydrogen strut, right? 669 00:30:27,880 --> 00:30:30,150 And on the other side, I've got a methyl. 670 00:30:30,150 --> 00:30:34,520 I've put a methyl here, like that. 671 00:30:34,520 --> 00:30:35,420 OK? 672 00:30:35,420 --> 00:30:36,240 Or actually, let's get-- 673 00:30:36,240 --> 00:30:37,080 OK, I'll do that. 674 00:30:37,080 --> 00:30:39,220 I was-- what I wanted to do, to get really-- 675 00:30:39,220 --> 00:30:40,000 OK, watch this. 676 00:30:40,000 --> 00:30:40,210 All right. 677 00:30:40,210 --> 00:30:42,360 So what I'm going to do on this side, 678 00:30:42,360 --> 00:30:43,250 this side, same thing. 679 00:30:43,250 --> 00:30:47,110 The carbon has a hydrogen strut down here, and on the 680 00:30:47,110 --> 00:30:50,130 other side, you've got the methyl. 681 00:30:50,130 --> 00:30:51,070 OK? 682 00:30:51,070 --> 00:30:52,410 So that looks good. 683 00:30:52,410 --> 00:30:56,140 But there's another way to do this, and still keep the 684 00:30:56,140 --> 00:30:58,000 carbon-carbon bond in the center. 685 00:30:58,000 --> 00:30:59,860 So I'm going to do that over here. 686 00:30:59,860 --> 00:31:02,090 So 1, 2, 1, 2. 687 00:31:02,090 --> 00:31:05,100 And in this instance, I'll put the same thing I have on the 688 00:31:05,100 --> 00:31:08,050 left side, H3C. 689 00:31:08,050 --> 00:31:09,310 So so far, so good. 690 00:31:09,310 --> 00:31:10,850 I've got the same molecule. 691 00:31:10,850 --> 00:31:13,330 But now what I'm going to do, just for grins and chuckles, 692 00:31:13,330 --> 00:31:17,300 I'm going to put the hydrogen in the upper position, and the 693 00:31:17,300 --> 00:31:20,480 methyl in the lower position. 694 00:31:20,480 --> 00:31:24,770 Now, these are not constitutional isomers. 695 00:31:24,770 --> 00:31:27,140 They have the same constitution, right? 696 00:31:27,140 --> 00:31:30,660 Carbon-carbon double bond, two methyl groups, two hydrogens. 697 00:31:30,660 --> 00:31:34,250 Carbon-carbon double bond, two methyl groups, two hydrogens. 698 00:31:34,250 --> 00:31:37,510 So they're constitutionally identical, yet these have very 699 00:31:37,510 --> 00:31:38,820 different properties. 700 00:31:38,820 --> 00:31:40,890 Can you see? 701 00:31:40,890 --> 00:31:42,790 I mean, the dipole moment is going to be different. 702 00:31:42,790 --> 00:31:43,010 Look. 703 00:31:43,010 --> 00:31:46,510 Here's the charge, all up on one side, and here the charge 704 00:31:46,510 --> 00:31:50,580 is more symmetrically straddled. 705 00:31:50,580 --> 00:31:53,300 Which means, they're going to have different melting points. 706 00:31:53,300 --> 00:31:55,020 They're going to have different boiling points. 707 00:31:55,020 --> 00:31:57,130 And they have the same chemical formula, and they 708 00:31:57,130 --> 00:32:00,390 have the same chemical constitution. 709 00:32:00,390 --> 00:32:01,520 So they're different kinds. 710 00:32:01,520 --> 00:32:03,040 There's some kind of isomers-- 711 00:32:03,040 --> 00:32:04,190 what's the difference here? 712 00:32:04,190 --> 00:32:07,210 It's not the constitution, it's the way things are 713 00:32:07,210 --> 00:32:08,510 arranged in space! 714 00:32:08,510 --> 00:32:10,250 This is great material science. 715 00:32:10,250 --> 00:32:12,590 Spatial orientation is everything. 716 00:32:12,590 --> 00:32:14,950 And what do you call it when you're listening to some 717 00:32:14,950 --> 00:32:18,840 loudspeakers and a really good audio system, and you can 718 00:32:18,840 --> 00:32:22,740 close your eyes, and the violins are over here, and the 719 00:32:22,740 --> 00:32:27,170 cello is here, and you can hear the 720 00:32:27,170 --> 00:32:28,370 percussion way in the back. 721 00:32:28,370 --> 00:32:30,230 What is that called? 722 00:32:30,230 --> 00:32:31,910 Stereophonic sound. 723 00:32:31,910 --> 00:32:36,940 Stereo phonic, meaning you can render spacial resolution. 724 00:32:36,940 --> 00:32:38,365 So these are called stereoisomers. 725 00:32:43,950 --> 00:32:46,090 One's a stereoisomer of the other. 726 00:32:46,090 --> 00:32:48,580 So they're spacially distinguishable. 727 00:32:48,580 --> 00:32:49,560 So they have-- 728 00:32:49,560 --> 00:32:52,710 for example, I went and looked this up. 729 00:32:52,710 --> 00:32:52,980 Oh. 730 00:32:52,980 --> 00:32:54,860 Let's give some names to this. 731 00:32:54,860 --> 00:32:59,080 In this case, all the methyls are on the same side, and the 732 00:32:59,080 --> 00:33:00,390 hydrogens are on the same side. 733 00:33:00,390 --> 00:33:04,450 So I can a dividing plane here, if you like, 734 00:33:04,450 --> 00:33:05,990 parallel to the floor. 735 00:33:05,990 --> 00:33:07,540 And I'll just cut right through the center of the 736 00:33:07,540 --> 00:33:09,980 carbons, parallel to the floor. 737 00:33:09,980 --> 00:33:13,420 And so in one instance, all the methyls are on the same 738 00:33:13,420 --> 00:33:15,940 side, and here the methyls are on opposite sides of the 739 00:33:15,940 --> 00:33:17,000 double bond. 740 00:33:17,000 --> 00:33:19,510 So when they're on the same side, this is called 741 00:33:19,510 --> 00:33:21,730 cis-butene. 742 00:33:21,730 --> 00:33:23,650 And let's be super pedantic. 743 00:33:23,650 --> 00:33:26,710 It was a 2-butene, so now it's a cis-2-butene. 744 00:33:29,290 --> 00:33:31,720 This is terrific. 745 00:33:31,720 --> 00:33:34,800 And this is a 2-butene, but it's on opposite side. 746 00:33:34,800 --> 00:33:36,253 So this is called a trans-2-butene. 747 00:33:38,820 --> 00:33:41,870 Cis-2-butene and trans-2-butene. 748 00:33:41,870 --> 00:33:46,940 And I looked up-- so let's see, which one do you think 749 00:33:46,940 --> 00:33:50,450 has tighter, which one's going to be more tightly packed? 750 00:33:50,450 --> 00:33:55,110 Which one's going to have the greater density? 751 00:33:55,110 --> 00:33:57,740 Which one's going to pack better? 752 00:33:57,740 --> 00:33:58,990 Cis or trans? 753 00:34:04,250 --> 00:34:16,740 The density here is 0.627, and the density here is 0.61. 754 00:34:16,740 --> 00:34:17,440 OK? 755 00:34:17,440 --> 00:34:22,370 Now, which one's going to have the higher boiling point? 756 00:34:22,370 --> 00:34:25,200 Which one's going to have the higher boiling point? 757 00:34:25,200 --> 00:34:26,530 Gee, that should be a no-brainer. 758 00:34:26,530 --> 00:34:28,250 Once you know which one's got the higher density. 759 00:34:28,250 --> 00:34:30,520 Why does it have the higher density? 760 00:34:30,520 --> 00:34:32,040 Because it's more nearest neighbors is 761 00:34:32,040 --> 00:34:33,050 more tightly packed. 762 00:34:33,050 --> 00:34:35,620 So I would bet on the one with the higher density. 763 00:34:35,620 --> 00:34:42,040 And this one boils at, boiling point is 3.7 degrees Celsius, 764 00:34:42,040 --> 00:34:45,040 and this one, the boiling point is-- 765 00:34:45,040 --> 00:34:48,270 hang on, I've got this backwards. 766 00:34:48,270 --> 00:34:49,370 This is 3.7. 767 00:34:49,370 --> 00:34:51,860 Boiling point is 1 degree Celsius. 768 00:34:51,860 --> 00:34:54,450 So those are the data as they come up. 769 00:34:54,450 --> 00:34:58,890 So stereoisomer, spacially distinguishable. 770 00:34:58,890 --> 00:35:01,210 By the way, we can form multiple bonds. 771 00:35:01,210 --> 00:35:03,320 We can form multiple double bonds. 772 00:35:03,320 --> 00:35:04,720 So they're -enes as well. 773 00:35:04,720 --> 00:35:10,990 So if we have two double bonds in the molecule, so we'll call 774 00:35:10,990 --> 00:35:12,600 that a diene. 775 00:35:15,240 --> 00:35:17,070 And we can have-- 776 00:35:17,070 --> 00:35:19,520 you can keep going with the Latin, but common ones you 777 00:35:19,520 --> 00:35:21,350 might find is the triene. 778 00:35:21,350 --> 00:35:23,920 And this will come back later when we look at polymers. 779 00:35:23,920 --> 00:35:27,040 So if we have two bonds, we will have-- 780 00:35:27,040 --> 00:35:33,680 You know, some of that hard luggage that you're seeing 781 00:35:33,680 --> 00:35:37,680 that's coming back, they got the roller boards, but instead 782 00:35:37,680 --> 00:35:39,940 of the fabric, now they're coming back with the really 783 00:35:39,940 --> 00:35:41,040 hard polymer? 784 00:35:41,040 --> 00:35:46,650 That's ABS, and the b is butadiene. 785 00:35:46,650 --> 00:35:49,080 So let's look at a-- here's a pentadiene. 786 00:35:49,080 --> 00:35:50,190 I'll give you a pentadiene. 787 00:35:50,190 --> 00:35:54,390 So that's going to be 1, 2, 3, 4, 5. 788 00:35:54,390 --> 00:35:56,510 It's five carbons, for starters. 789 00:35:56,510 --> 00:35:58,510 And I'm going to put the double bonds on 790 00:35:58,510 --> 00:36:00,240 the 1 and the 3 carbon. 791 00:36:00,240 --> 00:36:03,600 It'll be a penta-, it's five carbons. 792 00:36:03,600 --> 00:36:06,070 And it's an -ene, because there's going to be some 793 00:36:06,070 --> 00:36:07,450 double bonds here. 794 00:36:07,450 --> 00:36:10,040 And it's a di-, because I'm going to put double bonds at 795 00:36:10,040 --> 00:36:10,870 the 1 and the 3. 796 00:36:10,870 --> 00:36:14,510 So 1 gets a double bond, and 3 gets a double bond. 797 00:36:14,510 --> 00:36:18,100 So this is a pentadiene. 798 00:36:18,100 --> 00:36:19,040 OK? 799 00:36:19,040 --> 00:36:21,830 And then the last thing is-- 800 00:36:21,830 --> 00:36:22,370 pardon me. 801 00:36:22,370 --> 00:36:25,330 Last thing is radicals. 802 00:36:25,330 --> 00:36:27,310 So here's the common radical. 803 00:36:27,310 --> 00:36:34,770 We'll start with ethylene, and I'm going to make an ethylene 804 00:36:34,770 --> 00:36:35,395 radical here. 805 00:36:35,395 --> 00:36:39,440 I'll break off the hydrogen at this point, and I can write 806 00:36:39,440 --> 00:36:40,690 that as CH2CH. 807 00:36:45,580 --> 00:36:49,110 And we can't call this ethyl radical, because ethyl was 808 00:36:49,110 --> 00:36:52,130 already used for C2H5. 809 00:36:52,130 --> 00:36:55,070 So we need to indicate that there's a double bond, and so 810 00:36:55,070 --> 00:36:58,360 this radical is known as vinyl. 811 00:36:58,360 --> 00:37:01,010 This is the vinyl radical. 812 00:37:01,010 --> 00:37:04,020 And so you could react this with chlorine, for example, in 813 00:37:04,020 --> 00:37:07,260 which case you'd make vinyl chloride, and then you'd 814 00:37:07,260 --> 00:37:08,790 polymerize that, and you make PVC. 815 00:37:08,790 --> 00:37:13,070 And we're going to see that in the next coming days. 816 00:37:13,070 --> 00:37:16,040 Or you could you can put alcohol on there. 817 00:37:16,040 --> 00:37:17,690 I've already told you that. 818 00:37:17,690 --> 00:37:20,230 I don't need to remind you twice about that, I bet. 819 00:37:20,230 --> 00:37:20,570 OK. 820 00:37:20,570 --> 00:37:22,130 So now-- 821 00:37:22,130 --> 00:37:23,360 oh, there's one other one. 822 00:37:23,360 --> 00:37:25,570 There's one other one that will come up if you take a lot 823 00:37:25,570 --> 00:37:28,390 of biochemistry, and that's the one that 824 00:37:28,390 --> 00:37:29,650 comes off of propene. 825 00:37:29,650 --> 00:37:31,545 So if you start with propene, propene's going 826 00:37:31,545 --> 00:37:32,820 to look like this. 827 00:37:32,820 --> 00:37:36,000 1, 2, 3. 828 00:37:36,000 --> 00:37:37,120 So there's propene. 829 00:37:37,120 --> 00:37:37,990 3. 830 00:37:37,990 --> 00:37:42,770 There's a saying double bond here, and I'm going to put 1, 831 00:37:42,770 --> 00:37:44,550 2, 3 in here. 832 00:37:44,550 --> 00:37:48,470 1, 2, 3, 1, 2, 3. 833 00:37:48,470 --> 00:37:49,580 1, 2, 3, 4. 834 00:37:49,580 --> 00:37:50,260 OK. 835 00:37:50,260 --> 00:37:54,510 So this is the radical that comes from propene. 836 00:37:54,510 --> 00:38:01,790 So this one is derived from ethylene, and this one here is 837 00:38:01,790 --> 00:38:06,520 derived from propylene. 838 00:38:06,520 --> 00:38:09,990 So again, as in this case, we couldn't call this ethyl. 839 00:38:09,990 --> 00:38:12,280 We can't call this propyl, because that's the one that 840 00:38:12,280 --> 00:38:15,140 you get from the alkane. 841 00:38:15,140 --> 00:38:18,000 So instead, this one is called allyl. 842 00:38:18,000 --> 00:38:19,770 A L L Y L. 843 00:38:19,770 --> 00:38:24,950 And if you take 7012 at some point, Professor Weinberg will 844 00:38:24,950 --> 00:38:27,090 refer to these pendant groups. 845 00:38:27,090 --> 00:38:29,370 He likes to pronounce this all-YL. 846 00:38:29,370 --> 00:38:31,630 You'll hear him talk about, and the all-YLS are 847 00:38:31,630 --> 00:38:32,400 over here and here. 848 00:38:32,400 --> 00:38:35,330 That's what we're talking about. 849 00:38:35,330 --> 00:38:35,960 OK, good. 850 00:38:35,960 --> 00:38:41,560 So this is C3H7 dot. 851 00:38:41,560 --> 00:38:42,900 Good. 852 00:38:42,900 --> 00:38:43,300 All right. 853 00:38:43,300 --> 00:38:44,660 Moving right along. 854 00:38:44,660 --> 00:38:47,220 Now I want to turn to the alkynes. 855 00:38:50,230 --> 00:38:56,140 That's the sp hybridization. 856 00:38:56,140 --> 00:38:57,740 sp. 857 00:38:57,740 --> 00:39:01,590 And that means there's going to be at least one 858 00:39:01,590 --> 00:39:05,120 carbon-carbon triple bond. 859 00:39:05,120 --> 00:39:06,880 One carbon-carbon triple bond. 860 00:39:06,880 --> 00:39:14,010 So the formula there is CNH2N minus 2, and obviously N has 861 00:39:14,010 --> 00:39:16,590 to be greater than 1, otherwise you 862 00:39:16,590 --> 00:39:18,010 can't form a bond. 863 00:39:18,010 --> 00:39:20,300 And there's very little that you need to 864 00:39:20,300 --> 00:39:21,570 remember about this one. 865 00:39:21,570 --> 00:39:26,740 The dominant one that you'll come upon is C2H2. 866 00:39:30,250 --> 00:39:34,770 So according IUPAC nomenclature, the two carbons 867 00:39:34,770 --> 00:39:40,270 means it has to be F, and these are all alkynes, so this 868 00:39:40,270 --> 00:39:41,830 should be ethyne. 869 00:39:41,830 --> 00:39:44,080 And if you ask for ethyne, nobody knows what you're 870 00:39:44,080 --> 00:39:46,300 talking about, although it's very correct. 871 00:39:46,300 --> 00:39:51,830 This is known as acetylene, which is a fuel gas for 872 00:39:51,830 --> 00:39:54,720 welding, cutting, torches and so on. 873 00:39:54,720 --> 00:39:56,990 You've got two lines, you've got a big tank of acetylene, 874 00:39:56,990 --> 00:39:58,710 you've got a big tank of oxygen. 875 00:39:58,710 --> 00:40:02,340 And this is used because there is enormous energy stored in 876 00:40:02,340 --> 00:40:03,830 this carbon-carbon double bond. 877 00:40:03,830 --> 00:40:07,500 And so when you combust this with the stoichiometric amount 878 00:40:07,500 --> 00:40:14,400 of oxygen, you can cut through steel, you can use this to 879 00:40:14,400 --> 00:40:19,380 make very elaborate glassware with pure silica, making fused 880 00:40:19,380 --> 00:40:20,770 quartz glassware. 881 00:40:20,770 --> 00:40:23,830 Very, very high energy contained in here. 882 00:40:23,830 --> 00:40:28,900 And just to give one more example, let's look at 883 00:40:28,900 --> 00:40:32,370 something that's got four carbons in it. 884 00:40:32,370 --> 00:40:34,960 So it's going to have four carbons and a triple bond. 885 00:40:34,960 --> 00:40:38,490 So if it's 4, it's going to have the B U T but-, and it's 886 00:40:38,490 --> 00:40:39,430 going to need an -yne. 887 00:40:39,430 --> 00:40:41,090 So this will be a butyne. 888 00:40:41,090 --> 00:40:44,150 And depending on where we want to put the triple bond, I 889 00:40:44,150 --> 00:40:45,830 don't know, if you want to put a triple bond here, 890 00:40:45,830 --> 00:40:47,550 there's 1, 2, 3, 4. 891 00:40:47,550 --> 00:40:53,580 So this we could call 2-butyne, and it's C4H6, If 892 00:40:53,580 --> 00:40:58,510 you go through the stoichiometry. 893 00:40:58,510 --> 00:41:00,220 Let's try it, just for practice. 894 00:41:00,220 --> 00:41:03,720 So this carbon on the end is 1, 2, 3, 4. 895 00:41:03,720 --> 00:41:05,360 Look at the second carbon. 896 00:41:05,360 --> 00:41:09,130 It's got one strut bonding to the neighboring carbon, and 897 00:41:09,130 --> 00:41:11,170 three struts bonding to the neighboring 898 00:41:11,170 --> 00:41:12,610 carbon on the right. 899 00:41:12,610 --> 00:41:14,020 It's saturated now. 900 00:41:14,020 --> 00:41:15,740 Nothing comes of without carbon. 901 00:41:15,740 --> 00:41:16,380 Look at this one. 902 00:41:16,380 --> 00:41:18,090 1, 2, 3, 4. 903 00:41:18,090 --> 00:41:19,370 Nothing comes off of this one. 904 00:41:19,370 --> 00:41:21,130 And then finally 1, 2, 3. 905 00:41:21,130 --> 00:41:23,360 So there's three hydrogens here, there's three hydrogens 906 00:41:23,360 --> 00:41:25,070 here, there's your sixth hydrogen. 907 00:41:25,070 --> 00:41:26,740 C4H6. 908 00:41:26,740 --> 00:41:27,970 OK. 909 00:41:27,970 --> 00:41:30,280 That's good. 910 00:41:30,280 --> 00:41:30,630 All right. 911 00:41:30,630 --> 00:41:33,300 There's one other set that I want to look at, and these are 912 00:41:33,300 --> 00:41:35,790 called the arynes. 913 00:41:35,790 --> 00:41:37,342 These are aromatic hydrocarbons. 914 00:41:46,320 --> 00:41:49,860 Some people refer to them as arynes. 915 00:41:49,860 --> 00:41:55,770 And the most notable one is C6H6, which is benzine. 916 00:41:59,200 --> 00:42:05,670 And benzine's molecular weight was determined long ago, in 917 00:42:05,670 --> 00:42:07,400 the early 1800s. 918 00:42:07,400 --> 00:42:17,990 And it was Kekule who, in 1865, dared to suggest that 919 00:42:17,990 --> 00:42:29,400 the chemical structure of benzine was a ring structure. 920 00:42:29,400 --> 00:42:37,650 So Kekule suggested a carbon ring. 921 00:42:37,650 --> 00:42:42,030 Up until this time, people didn't have the common 922 00:42:42,030 --> 00:42:45,800 understanding that carbons could link to themselves, let 923 00:42:45,800 --> 00:42:47,410 alone form a ring. 924 00:42:47,410 --> 00:42:51,400 And so now, if we go through this, we will put, from each 925 00:42:51,400 --> 00:42:53,830 of these junctions there's the carbon, so we have to have 926 00:42:53,830 --> 00:42:54,580 four struts. 927 00:42:54,580 --> 00:43:00,580 We need hydrogen, so let's put hydrogens 1, 2, 3, 4, 5, 6, So 928 00:43:00,580 --> 00:43:03,790 there's the 6 hydrogens. 929 00:43:03,790 --> 00:43:05,880 And now, each carbon needs 4 struts. 930 00:43:05,880 --> 00:43:09,070 So 1, 2, 3, and I'll put a double bond. 931 00:43:09,070 --> 00:43:10,260 That will make 4. 932 00:43:10,260 --> 00:43:18,420 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4, and now this one here. 933 00:43:18,420 --> 00:43:20,720 So you have an alternating structure of double bond, 934 00:43:20,720 --> 00:43:24,160 single bond, double bond, single bond on the carbons. 935 00:43:24,160 --> 00:43:25,020 OK? 936 00:43:25,020 --> 00:43:30,100 So that's the way things stood until the twentieth century, 937 00:43:30,100 --> 00:43:36,730 when on the basis of new data, it was discovered that all 938 00:43:36,730 --> 00:43:39,110 carbon-carbon bonds-- 939 00:43:39,110 --> 00:43:41,610 and I don't want to make this a single bond, I'll just say 940 00:43:41,610 --> 00:43:48,940 all carbon-carbon bonds in benzine, C6H6, were measured 941 00:43:48,940 --> 00:43:52,200 to be the same length. 942 00:43:52,200 --> 00:43:54,660 Well, that's a problem, isn't it? 943 00:43:54,660 --> 00:43:57,850 That's a problem, because we would expect that, you know, 944 00:43:57,850 --> 00:44:01,970 we know that carbon-carbon single bond is about 1.47 945 00:44:01,970 --> 00:44:07,190 angstroms, and the carbon-carbon double bond has 946 00:44:07,190 --> 00:44:10,220 to be shorter, because it's double-bond, it's tighter, so 947 00:44:10,220 --> 00:44:12,070 it pulls things in. 948 00:44:12,070 --> 00:44:20,170 So that's 1.33 angstroms. And the measurement here was found 949 00:44:20,170 --> 00:44:27,230 to be 1.39 angstroms. And 1.39 angstroms is midway between 950 00:44:27,230 --> 00:44:29,410 1.47 and 1.33. 951 00:44:29,410 --> 00:44:33,160 So people were frustrated with this new information. 952 00:44:33,160 --> 00:44:37,820 And it was Linus Pauling who made sense of this for us. 953 00:44:37,820 --> 00:44:43,220 Pauling, who in 1931 came along and said, 954 00:44:43,220 --> 00:44:44,990 what we have a mix? 955 00:44:44,990 --> 00:44:47,420 What if we have a mix of two structures? 956 00:44:47,420 --> 00:44:53,510 And he said, suppose you had something that looked like so. 957 00:44:53,510 --> 00:44:55,530 1, 1, 1. 958 00:44:55,530 --> 00:44:59,970 So here's the set of double bonds off of the ring. 959 00:44:59,970 --> 00:45:05,970 And what if there is a resonance with an opposite 960 00:45:05,970 --> 00:45:09,740 hybrid, where this double bond, instead of being here, 961 00:45:09,740 --> 00:45:10,620 goes over to here? 962 00:45:10,620 --> 00:45:12,490 So now we have this? 963 00:45:12,490 --> 00:45:15,480 And he said, if the system resonated between the 964 00:45:15,480 --> 00:45:18,280 structure on the left and the structure on the right, the 965 00:45:18,280 --> 00:45:24,410 time average value of the carbon-carbon bond length 966 00:45:24,410 --> 00:45:32,470 would be around 1.39 angstroms. So this is a 967 00:45:32,470 --> 00:45:42,410 resonant hybrid structure, to account for the mix of single 968 00:45:42,410 --> 00:45:46,960 and double bonds, which gives rise to the current 969 00:45:46,960 --> 00:45:49,710 representation of benzine as simply this. 970 00:45:49,710 --> 00:45:51,610 So we're not saying this is single or double. 971 00:45:51,610 --> 00:45:55,570 It's a resonant between one and two. 972 00:45:55,570 --> 00:45:57,350 OK. 973 00:45:57,350 --> 00:46:00,000 The other thing is, if all of these bonds are the same 974 00:46:00,000 --> 00:46:05,190 length, and that means that between the 12:00 position 975 00:46:05,190 --> 00:46:10,170 here and the 2:00 position, there is pi bonding, and then 976 00:46:10,170 --> 00:46:14,020 along this double bond, there's pi bonding, and then 977 00:46:14,020 --> 00:46:17,760 along this double bond, there's pi bonding. 978 00:46:17,760 --> 00:46:20,940 But if all of the bonds are the same length, I can't say 979 00:46:20,940 --> 00:46:24,770 that the pi bonds are confined to where the double bonds are 980 00:46:24,770 --> 00:46:29,050 indicated, because resonance indicates that it could be 981 00:46:29,050 --> 00:46:30,500 between adjacents. 982 00:46:30,500 --> 00:46:32,190 So that means that the electrons, in 983 00:46:32,190 --> 00:46:34,960 fact, can go all around. 984 00:46:34,960 --> 00:46:40,040 So resonance, then, means that the pi electrons are 985 00:46:40,040 --> 00:46:41,290 delocalized. 986 00:46:49,050 --> 00:46:51,540 And now here's some better drawings. 987 00:46:51,540 --> 00:46:52,710 It's hard to draw that. 988 00:46:52,710 --> 00:46:53,680 So here they are. 989 00:46:53,680 --> 00:46:53,940 OK. 990 00:46:53,940 --> 00:46:55,800 So this is a nicer drawing of benzine. 991 00:46:55,800 --> 00:46:59,760 So you can see, when all of these bonds are resonant, it 992 00:46:59,760 --> 00:47:02,240 doesn't matter whether I choose this front one as the 993 00:47:02,240 --> 00:47:03,670 double bond, or the one next to it. 994 00:47:03,670 --> 00:47:06,290 They're all the same length, and so the electrons can go 995 00:47:06,290 --> 00:47:06,840 all around. 996 00:47:06,840 --> 00:47:09,920 And you can imagine, if I did this with graphite, and I kept 997 00:47:09,920 --> 00:47:15,710 going, well, if the electron can go here, then it means it 998 00:47:15,710 --> 00:47:17,640 can go here, which means it can go here, which means it 999 00:47:17,640 --> 00:47:18,340 can go everywhere. 1000 00:47:18,340 --> 00:47:21,490 Which is why graphite is an electronic conductor, because 1001 00:47:21,490 --> 00:47:24,180 of delocalized pi bonds. 1002 00:47:24,180 --> 00:47:24,760 OK. 1003 00:47:24,760 --> 00:47:26,300 This is 1-3-butadiene. 1004 00:47:26,300 --> 00:47:28,510 Double bond, single bond, double bond. 1005 00:47:28,510 --> 00:47:31,710 Again, all the same length, and you can hybridize, and-- 1006 00:47:31,710 --> 00:47:32,740 This is how you start making 1007 00:47:32,740 --> 00:47:34,890 electronically conducted polymers. 1008 00:47:34,890 --> 00:47:36,630 You just go double bond, single bond. 1009 00:47:36,630 --> 00:47:37,860 Double bond, single bond. 1010 00:47:37,860 --> 00:47:40,410 Smear. 1011 00:47:40,410 --> 00:47:41,480 That's it. 1012 00:47:41,480 --> 00:47:41,840 OK. 1013 00:47:41,840 --> 00:47:43,920 Let's jump over that. 1014 00:47:43,920 --> 00:47:48,770 Let's talk about Kekule So he studied architecture, switched 1015 00:47:48,770 --> 00:47:49,470 to chemistry. 1016 00:47:49,470 --> 00:47:51,990 And then he got a job in London, and he used to fall 1017 00:47:51,990 --> 00:47:54,022 asleep on the bus to his apartment. 1018 00:47:54,022 --> 00:47:55,820 And one day he was sleeping on the bus. 1019 00:47:55,820 --> 00:47:59,350 He woke up, and he'd been dreaming about carbon forming 1020 00:47:59,350 --> 00:48:01,860 chains in 1855. 1021 00:48:01,860 --> 00:48:04,090 And he proposed carbon chains. 1022 00:48:04,090 --> 00:48:06,770 And then he got a job as a professor in Belgium, at the 1023 00:48:06,770 --> 00:48:08,510 University of Ghent. 1024 00:48:08,510 --> 00:48:10,890 And one night he fell asleep at the fireplace, and he 1025 00:48:10,890 --> 00:48:14,500 dreamt of a benzine molecule as a snake biting its tail 1026 00:48:14,500 --> 00:48:16,900 while spinning. 1027 00:48:16,900 --> 00:48:20,230 And that's where he got the idea of the ring molecule. 1028 00:48:20,230 --> 00:48:23,710 All he knew was that this thing had a formula, C6H6. 1029 00:48:23,710 --> 00:48:25,510 And for this, he's dubbed the founder 1030 00:48:25,510 --> 00:48:26,800 of structural chemistry. 1031 00:48:26,800 --> 00:48:29,240 So what's this formula for success? 1032 00:48:29,240 --> 00:48:31,780 Well, he moved into chemistry from another field. 1033 00:48:31,780 --> 00:48:33,880 But to dream, you've got to get some sleep. 1034 00:48:33,880 --> 00:48:37,250 And I'm probably talking to one of the most sleep-deprived 1035 00:48:37,250 --> 00:48:39,940 populations on this campus. 1036 00:48:39,940 --> 00:48:42,150 So I urge you to get some sleep, and then maybe you'll 1037 00:48:42,150 --> 00:48:43,460 be able to dream. 1038 00:48:43,460 --> 00:48:44,310 Hey, don't make noise. 1039 00:48:44,310 --> 00:48:45,510 We've got two minutes left. 1040 00:48:45,510 --> 00:48:48,510 nobody's going anywhere. 1041 00:48:48,510 --> 00:48:49,350 All right. 1042 00:48:49,350 --> 00:48:54,780 So the next thing is, I want to talk a little bit about 1043 00:48:54,780 --> 00:48:58,170 octane ratings and automobiles, and how we go 1044 00:48:58,170 --> 00:49:01,900 from straight chains to chains of different lengths. 1045 00:49:01,900 --> 00:49:04,530 If you're looking at combustion, the idea is, you 1046 00:49:04,530 --> 00:49:07,730 admit gasoline, which vaporizes, and then the piston 1047 00:49:07,730 --> 00:49:10,050 comes up, and under high compression, 1048 00:49:10,050 --> 00:49:11,670 the spark plug fires. 1049 00:49:11,670 --> 00:49:14,490 When the spark plug fires, this causes an explosion which 1050 00:49:14,490 --> 00:49:16,790 then pushes the piston down, and then you've got the 1051 00:49:16,790 --> 00:49:19,730 camshaft that takes the vertical motion and converts 1052 00:49:19,730 --> 00:49:21,010 it to rotary motion. 1053 00:49:21,010 --> 00:49:22,920 Now, if you're running an automobile after a certain 1054 00:49:22,920 --> 00:49:26,980 period of time, the combustion chamber becomes so hot that 1055 00:49:26,980 --> 00:49:30,400 just admitting the fuel, having it vaporized, before 1056 00:49:30,400 --> 00:49:34,400 the piston has risen fully to get maximum compression, this 1057 00:49:34,400 --> 00:49:36,140 thing could just explode. 1058 00:49:36,140 --> 00:49:39,070 And when it explodes, it'll send the piston down, and it's 1059 00:49:39,070 --> 00:49:40,870 out of sequence with the other pistons. 1060 00:49:40,870 --> 00:49:42,100 And that's when you get the knocking. 1061 00:49:42,100 --> 00:49:44,170 Sometimes you're driving up hill, you hear this 1062 00:49:44,170 --> 00:49:45,890 [GRINDING SOUND]. 1063 00:49:45,890 --> 00:49:47,420 That's the knocking going on. 1064 00:49:47,420 --> 00:49:49,540 You need to get a tune-up, or switch to 1065 00:49:49,540 --> 00:49:51,200 higher octane gasoline. 1066 00:49:51,200 --> 00:49:52,410 So what's going on in here? 1067 00:49:52,410 --> 00:49:55,770 What you're doing, is you're changing the chemical 1068 00:49:55,770 --> 00:49:59,980 composition, the constitutional isomerization. 1069 00:49:59,980 --> 00:50:05,030 And you do that in the process by which you synthesize the 1070 00:50:05,030 --> 00:50:06,540 gasoline in the first place. 1071 00:50:06,540 --> 00:50:08,800 So the figure of merit is called octane number, which 1072 00:50:08,800 --> 00:50:11,970 was first instituted here in the United States. 1073 00:50:11,970 --> 00:50:14,620 And they started with 2-2-4-trimethyl-pentane. 1074 00:50:14,620 --> 00:50:17,810 It's an octane, but it's an octane that's 2-2-4. 1075 00:50:17,810 --> 00:50:18,980 Three methyl branches. 1076 00:50:18,980 --> 00:50:20,810 So that means there's only five left. 1077 00:50:20,810 --> 00:50:23,740 So it's a pentane with three methyl branches. 1078 00:50:23,740 --> 00:50:26,080 And that's called 100. 1079 00:50:26,080 --> 00:50:28,290 And then is 0 is heptane. 1080 00:50:28,290 --> 00:50:30,780 If you put heptane into the combustion chamber, you'll 1081 00:50:30,780 --> 00:50:31,920 knock yourself silly. 1082 00:50:31,920 --> 00:50:33,880 And the engine will just shake and shake and shake. 1083 00:50:33,880 --> 00:50:37,210 So gasolines have to be somewhere on that interval. 1084 00:50:37,210 --> 00:50:40,630 So there's the-- you know, if you tested and you had 1085 00:50:40,630 --> 00:50:43,210 something that was trimetylpentane, 90%, versus 1086 00:50:43,210 --> 00:50:45,700 10% heptane, you'd call it a 90% octane. 1087 00:50:45,700 --> 00:50:47,080 And you can have octane numbers higher 1088 00:50:47,080 --> 00:50:48,530 than 100, by the way. 1089 00:50:48,530 --> 00:50:50,820 It just depends on what the repression is. 1090 00:50:50,820 --> 00:50:54,700 And oddly enough, when you when you increase the octane, 1091 00:50:54,700 --> 00:50:57,510 you make the fuel more difficult to burn. 1092 00:50:57,510 --> 00:51:00,300 Because you want it to burn only on demand. 1093 00:51:00,300 --> 00:51:03,750 Fuel that just burns whenever it wants leads to random 1094 00:51:03,750 --> 00:51:06,440 events in the engine, and that's not good, if you want 1095 00:51:06,440 --> 00:51:10,210 to get good thrust. So oddly enough, high octane gasoline 1096 00:51:10,210 --> 00:51:12,910 requires more ignition than low octane. 1097 00:51:12,910 --> 00:51:14,760 And the additives are tetraethyl 1098 00:51:14,760 --> 00:51:16,480 lead or ethyl alcohol. 1099 00:51:16,480 --> 00:51:23,490 And from that, you know now, we get E10, which is gasohol, 1100 00:51:23,490 --> 00:51:24,840 10% alcohol. 1101 00:51:24,840 --> 00:51:28,720 E85 is 85% ethyl alcohol. 1102 00:51:28,720 --> 00:51:31,140 And all of this you get by synthesis. 1103 00:51:31,140 --> 00:51:33,500 You know, playing with the catalysts, temperatures, and 1104 00:51:33,500 --> 00:51:36,360 so on, to get the right mix to get good fuel, 1105 00:51:36,360 --> 00:51:37,380 and get good emissions. 1106 00:51:37,380 --> 00:51:39,825 And you can decide amongst yourselves whether going to 1107 00:51:39,825 --> 00:51:43,670 E85 high levels of ethanol, ethanol derived from corn, is 1108 00:51:43,670 --> 00:51:46,970 that smart, is that food for fuel? 1109 00:51:46,970 --> 00:51:50,710 You know, what's the sensible use of agriculture, algae, 1110 00:51:50,710 --> 00:51:51,960 switchgrass? 1111 00:51:51,960 --> 00:51:52,720 All of that stuff. 1112 00:51:52,720 --> 00:51:55,150 I mean, it's all loaded into here. 1113 00:51:55,150 --> 00:51:56,660 All loaded into here. 1114 00:51:56,660 --> 00:51:58,620 So yeah. 1115 00:51:58,620 --> 00:52:00,410 With that, I think we'll adjourn. 1116 00:52:00,410 --> 00:52:02,200 I'll see you on Wednesday.