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Dialogue: 0,0:00:00.00,0:00:01.75,Default,,0000,0000,0000,,
Dialogue: 0,0:00:01.75,0:00:05.02,Default,,0000,0000,0000,,Today, we'll be talking about\Nhow to separate enantiomers
Dialogue: 0,0:00:05.02,0:00:05.78,Default,,0000,0000,0000,,from each other.
Dialogue: 0,0:00:05.78,0:00:08.92,Default,,0000,0000,0000,,Enantiomers are like your\Nleft and right hands.
Dialogue: 0,0:00:08.92,0:00:10.61,Default,,0000,0000,0000,,They are mirror\Nimages of each other,
Dialogue: 0,0:00:10.61,0:00:12.88,Default,,0000,0000,0000,,but they look almost identical.
Dialogue: 0,0:00:12.88,0:00:16.63,Default,,0000,0000,0000,,Remember that much like we\Nuse right and left to describe
Dialogue: 0,0:00:16.63,0:00:20.76,Default,,0000,0000,0000,,which hand is which, scientists\Nuse the letters S and R
Dialogue: 0,0:00:20.76,0:00:23.36,Default,,0000,0000,0000,,to designate which\Nenantiomer is which,
Dialogue: 0,0:00:23.36,0:00:26.27,Default,,0000,0000,0000,,when you only have\None chiral center.
Dialogue: 0,0:00:26.27,0:00:29.26,Default,,0000,0000,0000,,However, when you have\Nmultiple chiral centers,
Dialogue: 0,0:00:29.26,0:00:32.31,Default,,0000,0000,0000,,there are other ways of\Ndesignating enantiomers.
Dialogue: 0,0:00:32.31,0:00:34.13,Default,,0000,0000,0000,,But we won't be getting\Ninto that today,
Dialogue: 0,0:00:34.13,0:00:36.92,Default,,0000,0000,0000,,because that's much\Nmore complicated.
Dialogue: 0,0:00:36.92,0:00:39.90,Default,,0000,0000,0000,,Here we have a set\Nof enantiomers.
Dialogue: 0,0:00:39.90,0:00:43.38,Default,,0000,0000,0000,,This is the S confirmation\Nof thalidomide,
Dialogue: 0,0:00:43.38,0:00:46.32,Default,,0000,0000,0000,,and here on the right\Nis the R confirmation.
Dialogue: 0,0:00:46.32,0:00:50.12,Default,,0000,0000,0000,,Why does it matter that we have\Ntwo different confirmations?
Dialogue: 0,0:00:50.12,0:00:53.17,Default,,0000,0000,0000,,Well, you can see the\Ndifference quite clearly
Dialogue: 0,0:00:53.17,0:00:55.93,Default,,0000,0000,0000,,at the chiral center,\Nwhere one of the groups
Dialogue: 0,0:00:55.93,0:01:00.10,Default,,0000,0000,0000,,points into the screen and the\Nother points out of the screen.
Dialogue: 0,0:01:00.10,0:01:04.32,Default,,0000,0000,0000,,And just because of the\Nsimple change in confirmation,
Dialogue: 0,0:01:04.32,0:01:08.12,Default,,0000,0000,0000,,that S version was found to\Nlead to terrible birth defects
Dialogue: 0,0:01:08.12,0:01:09.73,Default,,0000,0000,0000,,when consumed by mothers.
Dialogue: 0,0:01:09.73,0:01:12.66,Default,,0000,0000,0000,,And because of\Nthis, drug companies
Dialogue: 0,0:01:12.66,0:01:16.75,Default,,0000,0000,0000,,now try to make sure that the\Nactive ingredient in their drug
Dialogue: 0,0:01:16.75,0:01:19.90,Default,,0000,0000,0000,,is only one\Nparticular enantiomer.
Dialogue: 0,0:01:19.90,0:01:22.74,Default,,0000,0000,0000,,So how would we go about\Nseparating these two?
Dialogue: 0,0:01:22.74,0:01:25.43,Default,,0000,0000,0000,,One technique that you\Ncould use is chiral column
Dialogue: 0,0:01:25.43,0:01:26.77,Default,,0000,0000,0000,,chromatography.
Dialogue: 0,0:01:26.77,0:01:30.19,Default,,0000,0000,0000,,You would need a stationary\Nphase that is chiral,
Dialogue: 0,0:01:30.19,0:01:32.99,Default,,0000,0000,0000,,meaning something that\Nwill only bind either
Dialogue: 0,0:01:32.99,0:01:37.66,Default,,0000,0000,0000,,to the R confirmation or the\NS confirmation of your desired
Dialogue: 0,0:01:37.66,0:01:38.97,Default,,0000,0000,0000,,enantiomer.
Dialogue: 0,0:01:38.97,0:01:41.98,Default,,0000,0000,0000,,So how does the chiral\Nstationary phase only
Dialogue: 0,0:01:41.98,0:01:44.82,Default,,0000,0000,0000,,bind to one of the enantiomers?
Dialogue: 0,0:01:44.82,0:01:48.45,Default,,0000,0000,0000,,Picture the two enantiomers\Nas your right and left hand.
Dialogue: 0,0:01:48.45,0:01:51.09,Default,,0000,0000,0000,,If your right hand tries\Nto shake another person's
Dialogue: 0,0:01:51.09,0:01:55.23,Default,,0000,0000,0000,,right hand it seems normal,\Nthe two fit together properly.
Dialogue: 0,0:01:55.23,0:01:58.91,Default,,0000,0000,0000,,But if your right hand tries\Nto shake your own left hand,
Dialogue: 0,0:01:58.91,0:02:01.66,Default,,0000,0000,0000,,it doesn't seem like\Nthey line up quite right.
Dialogue: 0,0:02:01.66,0:02:03.90,Default,,0000,0000,0000,,That's the exact same\Nthing that happens
Dialogue: 0,0:02:03.90,0:02:08.28,Default,,0000,0000,0000,,with the chiral stationary\Nphase and the wrong enantiomer.
Dialogue: 0,0:02:08.28,0:02:11.41,Default,,0000,0000,0000,,Next, what you do is you'd load\Nthat mixture of enantiomers.
Dialogue: 0,0:02:11.41,0:02:15.43,Default,,0000,0000,0000,,So on top here, you\Nmight see that you
Dialogue: 0,0:02:15.43,0:02:19.24,Default,,0000,0000,0000,,have some kind of\Nband of your mixture.
Dialogue: 0,0:02:19.24,0:02:21.46,Default,,0000,0000,0000,,This is racemic,\Nmeaning that it has
Dialogue: 0,0:02:21.46,0:02:24.18,Default,,0000,0000,0000,,a 50/50 mixture of enantiomers.
Dialogue: 0,0:02:24.18,0:02:26.73,Default,,0000,0000,0000,,So that's what you're\Nseeing here in the yellow.
Dialogue: 0,0:02:26.73,0:02:28.58,Default,,0000,0000,0000,,If we take a closer\Nlook, you'll see
Dialogue: 0,0:02:28.58,0:02:34.60,Default,,0000,0000,0000,,that this has some\Nof the S confirmation
Dialogue: 0,0:02:34.60,0:02:36.100,Default,,0000,0000,0000,,and some of the R\Nconfirmation too thrown in.
Dialogue: 0,0:02:36.100,0:02:40.30,Default,,0000,0000,0000,,
Dialogue: 0,0:02:40.30,0:02:44.08,Default,,0000,0000,0000,,And as this moves through\Nthe stationary phase,
Dialogue: 0,0:02:44.08,0:02:48.22,Default,,0000,0000,0000,,so once you open up the\Nstop cock, what you'll see
Dialogue: 0,0:02:48.22,0:02:52.57,Default,,0000,0000,0000,,is that if the R\Nenantiomer was the one that
Dialogue: 0,0:02:52.57,0:02:55.39,Default,,0000,0000,0000,,binds tightly to the\Nstationary phase,
Dialogue: 0,0:02:55.39,0:02:57.95,Default,,0000,0000,0000,,it won't move very quickly.
Dialogue: 0,0:02:57.95,0:03:02.05,Default,,0000,0000,0000,,But with the S enantiomer,\Nit might be racing through
Dialogue: 0,0:03:02.05,0:03:03.78,Default,,0000,0000,0000,,since it's not\Nreally interacting
Dialogue: 0,0:03:03.78,0:03:06.13,Default,,0000,0000,0000,,that much with the\Nstationary phase,
Dialogue: 0,0:03:06.13,0:03:09.31,Default,,0000,0000,0000,,and prefers to interact\Nwith the mobile phase.
Dialogue: 0,0:03:09.31,0:03:14.11,Default,,0000,0000,0000,,Once you've collected all of\Nthe S enantiomers in your flask,
Dialogue: 0,0:03:14.11,0:03:16.25,Default,,0000,0000,0000,,all you'll have\Nleft in the column
Dialogue: 0,0:03:16.25,0:03:19.43,Default,,0000,0000,0000,,is the R enantiomer, which\Nis pretty tightly bound
Dialogue: 0,0:03:19.43,0:03:21.69,Default,,0000,0000,0000,,to the chiral stationary phase.
Dialogue: 0,0:03:21.69,0:03:24.41,Default,,0000,0000,0000,,Next, what you'd do is\Nwhen you have this column,
Dialogue: 0,0:03:24.41,0:03:26.66,Default,,0000,0000,0000,,you'd want to pour\Nin lots of solvent
Dialogue: 0,0:03:26.66,0:03:29.54,Default,,0000,0000,0000,,so that you can get the\NR enantiomer to come out.
Dialogue: 0,0:03:29.54,0:03:32.57,Default,,0000,0000,0000,,Because as this pushes\Ndown through the column,
Dialogue: 0,0:03:32.57,0:03:35.48,Default,,0000,0000,0000,,it will take the R\Nenantiomer with it,
Dialogue: 0,0:03:35.48,0:03:40.30,Default,,0000,0000,0000,,giving you just the R\Nenantiomer in your flask.
Dialogue: 0,0:03:40.30,0:03:44.27,Default,,0000,0000,0000,,And there you've done a\Nsuccessful chiral resolution.
Dialogue: 0,0:03:44.27,0:03:48.65,Default,,0000,0000,0000,,The same principle can also be\Napplied to gas chromatography.
Dialogue: 0,0:03:48.65,0:03:52.22,Default,,0000,0000,0000,,Let's quickly review how\Ngas chromatography works.
Dialogue: 0,0:03:52.22,0:03:57.71,Default,,0000,0000,0000,,You insert your sample in\Nhere, a gas flows through,
Dialogue: 0,0:03:57.71,0:04:01.07,Default,,0000,0000,0000,,and then it goes into\Nthis long to that
Dialogue: 0,0:04:01.07,0:04:03.91,Default,,0000,0000,0000,,contains the stationary\Nphase and mobile phase,
Dialogue: 0,0:04:03.91,0:04:06.24,Default,,0000,0000,0000,,and goes to the detector.
Dialogue: 0,0:04:06.24,0:04:09.43,Default,,0000,0000,0000,,And if we were to\Nzoom in on this--
Dialogue: 0,0:04:09.43,0:04:12.51,Default,,0000,0000,0000,,and draw this just\Nkind of a long tube--
Dialogue: 0,0:04:12.51,0:04:17.74,Default,,0000,0000,0000,,again what you'd see is that if\Nthis time the stationary phase
Dialogue: 0,0:04:17.74,0:04:21.97,Default,,0000,0000,0000,,was attracted to the\NS enantiomer instead,
Dialogue: 0,0:04:21.97,0:04:25.70,Default,,0000,0000,0000,,you'd see that the S enantiomer\Nis sticking to the sides,
Dialogue: 0,0:04:25.70,0:04:27.69,Default,,0000,0000,0000,,sticking to the\Nstationary phase,
Dialogue: 0,0:04:27.69,0:04:32.60,Default,,0000,0000,0000,,while the R enantiomer races\Nthrough with the mobile phase.
Dialogue: 0,0:04:32.60,0:04:34.83,Default,,0000,0000,0000,,So there are actually\Na number of other ways
Dialogue: 0,0:04:34.83,0:04:37.40,Default,,0000,0000,0000,,you can separate\Nenantiomers, but those
Dialogue: 0,0:04:37.40,0:04:39.70,Default,,0000,0000,0000,,tend to be much\Nmore complicated.
Dialogue: 0,0:04:39.70,0:04:42.59,Default,,0000,0000,0000,,These are just two of the\Ncommon ways you can do it.
Dialogue: 0,0:04:42.59,0:04:44.46,Default,,0000,0000,0000,,And in both of\Nthem, whether you're
Dialogue: 0,0:04:44.46,0:04:49.05,Default,,0000,0000,0000,,doing column chromatography with\Na solid stationary phase or gas
Dialogue: 0,0:04:49.05,0:04:52.29,Default,,0000,0000,0000,,chromatography was a\Nliquid stationary phase,
Dialogue: 0,0:04:52.29,0:04:56.49,Default,,0000,0000,0000,,the important thing to remember\Nis that your stationary phase
Dialogue: 0,0:04:56.49,0:05:01.02,Default,,0000,0000,0000,,should be chiral and bind to\Nthe enantiomer that you want.
Dialogue: 0,0:05:01.02,0:05:01.56,Default,,0000,0000,0000,,