[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:02.32,0:00:04.45,Default,,0000,0000,0000,,- [Voiceover] Let's say we\Nwere asked to name the molecule
Dialogue: 0,0:00:04.45,0:00:06.12,Default,,0000,0000,0000,,on the top left.
Dialogue: 0,0:00:06.12,0:00:08.29,Default,,0000,0000,0000,,We would start by numbering our carbons.
Dialogue: 0,0:00:08.29,0:00:12.49,Default,,0000,0000,0000,,So this would be carbon\None, two, three, and four.
Dialogue: 0,0:00:12.49,0:00:16.15,Default,,0000,0000,0000,,Notice we have a double\Nbond starting at carbon two.
Dialogue: 0,0:00:16.15,0:00:19.72,Default,,0000,0000,0000,,So the name of this\Nmolecule would be 2-butene.
Dialogue: 0,0:00:19.72,0:00:23.29,Default,,0000,0000,0000,,Two because we have our double\Nbond starting at carbon two.
Dialogue: 0,0:00:23.29,0:00:26.35,Default,,0000,0000,0000,,"But" because we have four\Ncarbons and "ene" because
Dialogue: 0,0:00:26.35,0:00:29.03,Default,,0000,0000,0000,,we have a double bond\Npresence in the molecule.
Dialogue: 0,0:00:29.03,0:00:31.98,Default,,0000,0000,0000,,What about naming the\Nmolecule on the right?
Dialogue: 0,0:00:31.98,0:00:36.29,Default,,0000,0000,0000,,We number our carbons\None, two, three, and four.
Dialogue: 0,0:00:36.29,0:00:40.23,Default,,0000,0000,0000,,And once again we have a double\Nbond starting at carbon two.
Dialogue: 0,0:00:40.23,0:00:44.34,Default,,0000,0000,0000,,So the name of this\Nmolecule would be 2-butene.
Dialogue: 0,0:00:44.34,0:00:47.42,Default,,0000,0000,0000,,However these are two\Ndifferent molecules and
Dialogue: 0,0:00:47.42,0:00:50.35,Default,,0000,0000,0000,,the reason why is because\Nthere's no free rotation
Dialogue: 0,0:00:50.35,0:00:52.09,Default,,0000,0000,0000,,around a double bond.
Dialogue: 0,0:00:52.09,0:00:55.75,Default,,0000,0000,0000,,Single bonds have free rotation\Nbut double bonds don't.
Dialogue: 0,0:00:55.75,0:00:58.68,Default,,0000,0000,0000,,So you couldn't rotate the\Nmolecule on the left to
Dialogue: 0,0:00:58.68,0:01:01.15,Default,,0000,0000,0000,,look like the molecule on the right.
Dialogue: 0,0:01:01.15,0:01:04.38,Default,,0000,0000,0000,,Therefore they must be\Nisomers of each other
Dialogue: 0,0:01:04.38,0:01:08.29,Default,,0000,0000,0000,,and we need a way to\Ndistinguish between our isomers.
Dialogue: 0,0:01:08.29,0:01:12.55,Default,,0000,0000,0000,,And so one way to do that is\Nto use cis/trans terminology.
Dialogue: 0,0:01:12.55,0:01:14.62,Default,,0000,0000,0000,,So if we look at the molecule on the left,
Dialogue: 0,0:01:14.62,0:01:17.52,Default,,0000,0000,0000,,we can see we have two methyl groups.
Dialogue: 0,0:01:17.52,0:01:20.95,Default,,0000,0000,0000,,And those two methyl\Ngroups are on the same side
Dialogue: 0,0:01:20.95,0:01:22.55,Default,,0000,0000,0000,,of our double bond.
Dialogue: 0,0:01:22.55,0:01:25.49,Default,,0000,0000,0000,,So if I draw a line in here,\Nit's easier to see those two
Dialogue: 0,0:01:25.49,0:01:27.95,Default,,0000,0000,0000,,methyl groups are on the same sides.
Dialogue: 0,0:01:27.95,0:01:30.37,Default,,0000,0000,0000,,And we call that the cis isomer.
Dialogue: 0,0:01:30.37,0:01:32.72,Default,,0000,0000,0000,,So we put cis in front of our name here.
Dialogue: 0,0:01:32.72,0:01:34.82,Default,,0000,0000,0000,,I'm attempting to write it in italics.
Dialogue: 0,0:01:34.82,0:01:37.25,Default,,0000,0000,0000,,So this would be cis-2-butene.
Dialogue: 0,0:01:37.25,0:01:39.32,Default,,0000,0000,0000,,On the right when we look\Nat those methyl groups,
Dialogue: 0,0:01:39.32,0:01:42.02,Default,,0000,0000,0000,,these two methyl groups\Nare on opposite sides
Dialogue: 0,0:01:42.02,0:01:43.05,Default,,0000,0000,0000,,of the double bond.
Dialogue: 0,0:01:43.05,0:01:45.95,Default,,0000,0000,0000,,So I draw a line in here\Nto make it easier to see
Dialogue: 0,0:01:45.95,0:01:49.42,Default,,0000,0000,0000,,those two methyl groups\Nare on opposite sides.
Dialogue: 0,0:01:49.42,0:01:51.29,Default,,0000,0000,0000,,And we call that trans.
Dialogue: 0,0:01:51.29,0:01:53.12,Default,,0000,0000,0000,,So this is trans isomer.
Dialogue: 0,0:01:53.12,0:01:56.79,Default,,0000,0000,0000,,I'm going to write trans here\Nin italics, attempt to anyway.
Dialogue: 0,0:01:56.79,0:02:00.09,Default,,0000,0000,0000,,So we have cis-2-butene\Nand trans-2-butene.
Dialogue: 0,0:02:00.09,0:02:04.22,Default,,0000,0000,0000,,These are different molecules\Nwith different properties.
Dialogue: 0,0:02:04.22,0:02:06.25,Default,,0000,0000,0000,,If you want to use cis/trans terminology,
Dialogue: 0,0:02:06.25,0:02:08.82,Default,,0000,0000,0000,,you're looking for two identical groups
Dialogue: 0,0:02:08.82,0:02:10.49,Default,,0000,0000,0000,,and you are comparing them.
Dialogue: 0,0:02:10.49,0:02:13.25,Default,,0000,0000,0000,,So let's look at these next two\Nexamples here and figure out
Dialogue: 0,0:02:13.25,0:02:16.35,Default,,0000,0000,0000,,which one is cis and which one is trans.
Dialogue: 0,0:02:16.35,0:02:18.82,Default,,0000,0000,0000,,We're looking for identical groups.
Dialogue: 0,0:02:18.82,0:02:21.05,Default,,0000,0000,0000,,So over here we have\Nan ethyl group attached
Dialogue: 0,0:02:21.05,0:02:22.25,Default,,0000,0000,0000,,to our double bond
Dialogue: 0,0:02:22.25,0:02:25.22,Default,,0000,0000,0000,,and on the right we have an\Nethyl group to our double bond.
Dialogue: 0,0:02:25.22,0:02:28.12,Default,,0000,0000,0000,,Those two ethyl groups\Nare on the same side of
Dialogue: 0,0:02:28.12,0:02:32.10,Default,,0000,0000,0000,,our double bond so this\Nmust be the cis isomer.
Dialogue: 0,0:02:32.10,0:02:35.62,Default,,0000,0000,0000,,On the right we have this ethyl\Ngroup and this ethyl group
Dialogue: 0,0:02:35.62,0:02:38.85,Default,,0000,0000,0000,,on opposite sides of our double bond.
Dialogue: 0,0:02:38.85,0:02:42.15,Default,,0000,0000,0000,,So that must be the trans isomer.
Dialogue: 0,0:02:42.15,0:02:43.92,Default,,0000,0000,0000,,All right, let's do some more examples.
Dialogue: 0,0:02:43.92,0:02:45.89,Default,,0000,0000,0000,,I'll go down to here.
Dialogue: 0,0:02:45.89,0:02:49.32,Default,,0000,0000,0000,,On the left we have\Ncinnamaldehyde molecule.
Dialogue: 0,0:02:49.32,0:02:52.58,Default,,0000,0000,0000,,We're looking for two\Nidentical groups so we can use
Dialogue: 0,0:02:52.58,0:02:54.41,Default,,0000,0000,0000,,cis or trans.
Dialogue: 0,0:02:54.41,0:02:56.59,Default,,0000,0000,0000,,You can also use hydrogens, right.
Dialogue: 0,0:02:56.59,0:02:59.05,Default,,0000,0000,0000,,You don't have to use a\Nmethyl group or an ethyl group
Dialogue: 0,0:02:59.05,0:03:01.75,Default,,0000,0000,0000,,so if we look at our double\Nbond we know there's a
Dialogue: 0,0:03:01.75,0:03:03.85,Default,,0000,0000,0000,,hydrogen attached to this carbon
Dialogue: 0,0:03:03.85,0:03:06.79,Default,,0000,0000,0000,,and we know there's a hydrogen\Nattached to this carbon.
Dialogue: 0,0:03:06.79,0:03:10.55,Default,,0000,0000,0000,,And those two hydrogens are\Non opposite sides of our
Dialogue: 0,0:03:10.55,0:03:11.65,Default,,0000,0000,0000,,double bonds.
Dialogue: 0,0:03:11.65,0:03:14.52,Default,,0000,0000,0000,,And I'm drawing a line here\Nto make it easier to see.
Dialogue: 0,0:03:14.52,0:03:17.07,Default,,0000,0000,0000,,Right, these two hydrogens\Nare on opposite side
Dialogue: 0,0:03:17.07,0:03:19.69,Default,,0000,0000,0000,,so we're talking about trans here.
Dialogue: 0,0:03:19.69,0:03:23.07,Default,,0000,0000,0000,,Those hydrogens are\Nacross from each other.
Dialogue: 0,0:03:23.07,0:03:26.87,Default,,0000,0000,0000,,What about the tetra-substituted alkene
Dialogue: 0,0:03:26.87,0:03:29.00,Default,,0000,0000,0000,,on the right?
Dialogue: 0,0:03:29.00,0:03:32.72,Default,,0000,0000,0000,,We need two identical\Ngroups to use our cis/trans
Dialogue: 0,0:03:32.72,0:03:35.55,Default,,0000,0000,0000,,and here we have an ethyl\Ngroup, and here we have
Dialogue: 0,0:03:35.55,0:03:36.82,Default,,0000,0000,0000,,an ethyl group.
Dialogue: 0,0:03:36.82,0:03:38.79,Default,,0000,0000,0000,,All right over here we\Nhave a methyl group and an
Dialogue: 0,0:03:38.79,0:03:40.15,Default,,0000,0000,0000,,isopropyl group.
Dialogue: 0,0:03:40.15,0:03:43.32,Default,,0000,0000,0000,,But the two methyl groups\Nare on the same side of
Dialogue: 0,0:03:43.32,0:03:44.45,Default,,0000,0000,0000,,our double bond.
Dialogue: 0,0:03:44.45,0:03:49.45,Default,,0000,0000,0000,,So I draw a line in here and\Nwe see that these two groups
Dialogue: 0,0:03:49.59,0:03:51.19,Default,,0000,0000,0000,,are on the same side,
Dialogue: 0,0:03:51.19,0:03:54.69,Default,,0000,0000,0000,,therefore we're talking about cis here.
Dialogue: 0,0:03:54.69,0:03:58.25,Default,,0000,0000,0000,,So this double bond has\Na cis configuration.
Dialogue: 0,0:03:58.25,0:04:00.32,Default,,0000,0000,0000,,Let's compare the drawing\Non the left to the
Dialogue: 0,0:04:00.32,0:04:02.01,Default,,0000,0000,0000,,drawing on the right.
Dialogue: 0,0:04:02.01,0:04:03.82,Default,,0000,0000,0000,,The first time you look\Nat these two drawings
Dialogue: 0,0:04:03.82,0:04:06.09,Default,,0000,0000,0000,,you might think these are two isomers,
Dialogue: 0,0:04:06.09,0:04:09.19,Default,,0000,0000,0000,,and I could use cis/trans\Nterminology to distinguish
Dialogue: 0,0:04:09.19,0:04:10.38,Default,,0000,0000,0000,,between them.
Dialogue: 0,0:04:10.38,0:04:12.85,Default,,0000,0000,0000,,However, you can't because these are
Dialogue: 0,0:04:12.85,0:04:16.29,Default,,0000,0000,0000,,just two ways to represent\Nthe same molecule.
Dialogue: 0,0:04:16.29,0:04:18.42,Default,,0000,0000,0000,,If you picked up this\Nmolecule on the left and
Dialogue: 0,0:04:18.42,0:04:19.93,Default,,0000,0000,0000,,you flipped it up,
Dialogue: 0,0:04:19.93,0:04:22.82,Default,,0000,0000,0000,,you would get the drawing on the right.
Dialogue: 0,0:04:22.82,0:04:24.58,Default,,0000,0000,0000,,So they're not isomers of each other.
Dialogue: 0,0:04:24.58,0:04:27.08,Default,,0000,0000,0000,,This is the same molecule.
Dialogue: 0,0:04:27.08,0:04:31.19,Default,,0000,0000,0000,,And a fast way to figure that\Nout is to look at this carbon.
Dialogue: 0,0:04:31.19,0:04:34.85,Default,,0000,0000,0000,,And you can see you have\Ntwo identical groups bonded
Dialogue: 0,0:04:34.85,0:04:36.75,Default,,0000,0000,0000,,to that carbon.
Dialogue: 0,0:04:36.75,0:04:39.64,Default,,0000,0000,0000,,So you can't use cis/trans terminology.
Dialogue: 0,0:04:39.64,0:04:42.69,Default,,0000,0000,0000,,That's different from the\Nexample we did a minute ago.
Dialogue: 0,0:04:42.69,0:04:44.61,Default,,0000,0000,0000,,We had two identical groups,
Dialogue: 0,0:04:44.61,0:04:46.59,Default,,0000,0000,0000,,right these two ethyl groups here.
Dialogue: 0,0:04:46.59,0:04:49.12,Default,,0000,0000,0000,,However those two ethyl\Ngroups weren't bonded
Dialogue: 0,0:04:49.12,0:04:50.55,Default,,0000,0000,0000,,to the same carbon.
Dialogue: 0,0:04:50.55,0:04:53.62,Default,,0000,0000,0000,,Those two ethyl groups are\Nbonded to different carbons.
Dialogue: 0,0:04:53.62,0:04:56.49,Default,,0000,0000,0000,,So this ethyl group is bonded\Nto this carbon, and this
Dialogue: 0,0:04:56.49,0:04:59.08,Default,,0000,0000,0000,,ethyl group is bonded to this carbon.
Dialogue: 0,0:04:59.08,0:05:02.61,Default,,0000,0000,0000,,So we were able to use\Ncis/trans terminologies.
Dialogue: 0,0:05:02.61,0:05:04.82,Default,,0000,0000,0000,,So we looked at our\Ndouble bond and we said
Dialogue: 0,0:05:04.82,0:05:06.99,Default,,0000,0000,0000,,those two ethyl groups\Nare on the same side of
Dialogue: 0,0:05:06.99,0:05:08.12,Default,,0000,0000,0000,,our double bond,
Dialogue: 0,0:05:08.12,0:05:12.17,Default,,0000,0000,0000,,so this represents a cis\Nconfiguration of the double bond.
Dialogue: 0,0:05:12.17,0:05:14.68,Default,,0000,0000,0000,,So we can't do that up here because
Dialogue: 0,0:05:14.68,0:05:17.39,Default,,0000,0000,0000,,while we do have two identical groups,
Dialogue: 0,0:05:17.39,0:05:21.62,Default,,0000,0000,0000,,those identical groups are\Nbonded to the same carbon.