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Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:17.00,0:00:18.98,Default,,0000,0000,0000,,In the early days of organic chemistry,
Dialogue: 0,0:00:19.00,0:00:21.98,Default,,0000,0000,0000,,chemists understood\Nthat molecules were made of atoms
Dialogue: 0,0:00:22.00,0:00:23.98,Default,,0000,0000,0000,,connected through chemical bonds.
Dialogue: 0,0:00:24.00,0:00:26.98,Default,,0000,0000,0000,,However, the three-dimensional\Nshapes of molecules
Dialogue: 0,0:00:27.00,0:00:30.98,Default,,0000,0000,0000,,were utterly unclear, since they couldn't\Nbe observed directly.
Dialogue: 0,0:00:31.00,0:00:33.98,Default,,0000,0000,0000,,Molecules were represented using\Nsimple connectivity graphs
Dialogue: 0,0:00:34.00,0:00:36.98,Default,,0000,0000,0000,,like the one you see here.
Dialogue: 0,0:00:37.00,0:00:39.98,Default,,0000,0000,0000,,It was clear to savvy chemists\Nof the mid-19th century
Dialogue: 0,0:00:40.00,0:00:43.98,Default,,0000,0000,0000,,that these flat representations\Ncouldn't explain
Dialogue: 0,0:00:44.00,0:00:45.98,Default,,0000,0000,0000,,many of their observations.
Dialogue: 0,0:00:46.00,0:00:48.98,Default,,0000,0000,0000,,But chemical theory hadn't provided\Na satisfactory explanation
Dialogue: 0,0:00:49.00,0:00:51.38,Default,,0000,0000,0000,,for the three-dimensional\Nstructures of molecules.
Dialogue: 0,0:00:51.40,0:00:56.98,Default,,0000,0000,0000,,In 1874, the chemist Van't Hoff\Npublished a remarkable hypothesis:
Dialogue: 0,0:00:57.00,0:01:00.98,Default,,0000,0000,0000,,the four bonds of a saturated carbon atom
Dialogue: 0,0:01:01.00,0:01:02.98,Default,,0000,0000,0000,,point to the corners of a tetrahedron.
Dialogue: 0,0:01:03.00,0:01:05.98,Default,,0000,0000,0000,,It would take over 25 years
Dialogue: 0,0:01:06.00,0:01:09.98,Default,,0000,0000,0000,,for the quantum revolution\Nto theoretically validate his hypothesis.
Dialogue: 0,0:01:10.00,0:01:13.98,Default,,0000,0000,0000,,But Van't Hoff supported\Nhis theory using optical rotation.
Dialogue: 0,0:01:14.00,0:01:17.14,Default,,0000,0000,0000,,Van't Hoff noticed that only compounds\Ncontaining a central carbon
Dialogue: 0,0:01:17.17,0:01:20.98,Default,,0000,0000,0000,,bound to four different atoms or groups
Dialogue: 0,0:01:21.00,0:01:23.98,Default,,0000,0000,0000,,rotated plane-polarized light.
Dialogue: 0,0:01:24.00,0:01:25.98,Default,,0000,0000,0000,,Clearly there's something unique\Nabout this class of compounds.
Dialogue: 0,0:01:26.00,0:01:28.98,Default,,0000,0000,0000,,Take a look at the two molecules\Nyou see here.
Dialogue: 0,0:01:29.00,0:01:33.98,Default,,0000,0000,0000,,Each one is characterized\Nby a central, tetrahedral carbon atom
Dialogue: 0,0:01:34.00,0:01:35.98,Default,,0000,0000,0000,,bound to four different atoms:
Dialogue: 0,0:01:36.00,0:01:38.98,Default,,0000,0000,0000,,bromine, chlorine, fluorine, and hydrogen.
Dialogue: 0,0:01:39.00,0:01:41.57,Default,,0000,0000,0000,,We might be tempted to conclude\Nthat the two molecules
Dialogue: 0,0:01:41.60,0:01:44.98,Default,,0000,0000,0000,,are the same, if we just concern\Nourselves with what they're made of.
Dialogue: 0,0:01:45.00,0:01:47.98,Default,,0000,0000,0000,,However, let's see if we can\Noverlay the two molecules
Dialogue: 0,0:01:48.00,0:01:50.98,Default,,0000,0000,0000,,perfectly to really prove\Nthat they're the same.
Dialogue: 0,0:01:51.00,0:01:54.98,Default,,0000,0000,0000,,We have free license to rotate\Nand translate both of the molecules
Dialogue: 0,0:01:55.00,0:01:57.98,Default,,0000,0000,0000,,as we wish. Remarkably though,
Dialogue: 0,0:01:58.00,0:01:59.98,Default,,0000,0000,0000,,no matter how we move the molecules,
Dialogue: 0,0:02:00.00,0:02:03.98,Default,,0000,0000,0000,,we find that perfect superposition\Nis impossible to achieve.
Dialogue: 0,0:02:04.00,0:02:06.98,Default,,0000,0000,0000,,Now take a look at your hands.
Dialogue: 0,0:02:07.00,0:02:09.98,Default,,0000,0000,0000,,Notice that your two hands\Nhave all the same parts:
Dialogue: 0,0:02:10.00,0:02:13.98,Default,,0000,0000,0000,,a thumb, fingers, a palm, etc.
Dialogue: 0,0:02:14.00,0:02:16.98,Default,,0000,0000,0000,,Like our two molecules under study,
Dialogue: 0,0:02:17.00,0:02:19.98,Default,,0000,0000,0000,,both of your hands are made\Nof the same stuff.
Dialogue: 0,0:02:20.00,0:02:24.98,Default,,0000,0000,0000,,Furthermore, the distances between stuff\Nin both of your hands are the same.
Dialogue: 0,0:02:25.00,0:02:27.19,Default,,0000,0000,0000,,The index finger\Nis next to the middle finger,
Dialogue: 0,0:02:27.22,0:02:29.98,Default,,0000,0000,0000,,which is next to the ring finger, etc.
Dialogue: 0,0:02:30.00,0:02:32.98,Default,,0000,0000,0000,,The same is true\Nof our hypothetical molecules.
Dialogue: 0,0:02:33.00,0:02:34.98,Default,,0000,0000,0000,,All of their internal distances
Dialogue: 0,0:02:35.00,0:02:37.98,Default,,0000,0000,0000,,are the same. Despite\Nthe similarities between them,
Dialogue: 0,0:02:38.00,0:02:39.98,Default,,0000,0000,0000,,your hands, and our molecules,
Dialogue: 0,0:02:40.00,0:02:42.98,Default,,0000,0000,0000,,are certainly not the same.
Dialogue: 0,0:02:43.00,0:02:45.98,Default,,0000,0000,0000,,Try superimposing\Nyour hands on one another.
Dialogue: 0,0:02:46.00,0:02:47.98,Default,,0000,0000,0000,,Just like our molecules from before,
Dialogue: 0,0:02:48.00,0:02:50.98,Default,,0000,0000,0000,,you'll find that it can't\Nbe done perfectly.
Dialogue: 0,0:02:51.00,0:02:53.98,Default,,0000,0000,0000,,Now, point your palms toward one another.
Dialogue: 0,0:02:54.00,0:02:55.98,Default,,0000,0000,0000,,Wiggle both of your index fingers.
Dialogue: 0,0:02:56.00,0:02:59.98,Default,,0000,0000,0000,,Notice that your left hand\Nlooks as if it's looking
Dialogue: 0,0:03:00.00,0:03:01.98,Default,,0000,0000,0000,,in a mirror at your right.
Dialogue: 0,0:03:02.00,0:03:04.98,Default,,0000,0000,0000,,In other words, your hands\Nare mirror images.
Dialogue: 0,0:03:05.00,0:03:07.98,Default,,0000,0000,0000,,The same can be said of our molecules.
Dialogue: 0,0:03:08.00,0:03:10.98,Default,,0000,0000,0000,,We can turn them so\Nthat one looks at the other
Dialogue: 0,0:03:11.00,0:03:13.98,Default,,0000,0000,0000,,as in a mirror. Your hands\N- and our molecules -
Dialogue: 0,0:03:14.00,0:03:17.98,Default,,0000,0000,0000,,possess a spatial property\Nin common called chirality,
Dialogue: 0,0:03:18.00,0:03:19.98,Default,,0000,0000,0000,,or handedness.
Dialogue: 0,0:03:20.00,0:03:22.98,Default,,0000,0000,0000,,Chirality means exactly\Nwhat we've just described:
Dialogue: 0,0:03:23.00,0:03:25.48,Default,,0000,0000,0000,,a chiral object is not\Nthe same as its mirror image.
Dialogue: 0,0:03:25.50,0:03:29.98,Default,,0000,0000,0000,,Chiral objects are very special\Nin both chemistry and everyday life.
Dialogue: 0,0:03:30.00,0:03:32.98,Default,,0000,0000,0000,,Screws, for example, are also chiral.
Dialogue: 0,0:03:33.00,0:03:36.98,Default,,0000,0000,0000,,That's why we need the terms\Nright-handed and left-handed screws.
Dialogue: 0,0:03:37.00,0:03:39.98,Default,,0000,0000,0000,,And believe it or not,\Ncertain types of light
Dialogue: 0,0:03:40.00,0:03:41.98,Default,,0000,0000,0000,,can behave like chiral screws.
Dialogue: 0,0:03:42.00,0:03:46.98,Default,,0000,0000,0000,,Packed into every linear,\Nplane-polarized beam of light
Dialogue: 0,0:03:47.00,0:03:49.98,Default,,0000,0000,0000,,are right-handed and left-handed parts
Dialogue: 0,0:03:50.00,0:03:54.98,Default,,0000,0000,0000,,that rotate together\Nto produce plane polarization.
Dialogue: 0,0:03:55.00,0:03:57.98,Default,,0000,0000,0000,,Chiral molecules, placed\Nin a beam of such light,
Dialogue: 0,0:03:58.00,0:04:00.98,Default,,0000,0000,0000,,interact differently\Nwith the two chiral components.
Dialogue: 0,0:04:01.00,0:04:05.98,Default,,0000,0000,0000,,As a result, one component of the light\Ngets temporarily slowed down
Dialogue: 0,0:04:06.00,0:04:08.98,Default,,0000,0000,0000,,relative to the other. The\Neffect on the light beam
Dialogue: 0,0:04:09.00,0:04:12.98,Default,,0000,0000,0000,,is a rotation of its plane\Nfrom the original one,
Dialogue: 0,0:04:13.00,0:04:15.98,Default,,0000,0000,0000,,otherwise known as optical rotation.
Dialogue: 0,0:04:16.00,0:04:20.98,Default,,0000,0000,0000,,Van't Hoff and later chemists\Nrealized that the chiral nature
Dialogue: 0,0:04:21.00,0:04:24.00,Default,,0000,0000,0000,,of tetrahedral carbons can explain\Nthis fascinating phenomenon.
Dialogue: 0,0:04:24.02,0:04:28.98,Default,,0000,0000,0000,,Chirality is responsible for all kinds\Nof other fascinating effects
Dialogue: 0,0:04:29.00,0:04:30.98,Default,,0000,0000,0000,,in chemistry, and everyday life.
Dialogue: 0,0:04:31.00,0:04:33.98,Default,,0000,0000,0000,,Humans tend to love symmetry
Dialogue: 0,0:04:34.00,0:04:35.98,Default,,0000,0000,0000,,and so if you look around you,\Nyou'll find that chiral objects
Dialogue: 0,0:04:36.00,0:04:37.98,Default,,0000,0000,0000,,made by humans are rare.
Dialogue: 0,0:04:38.00,0:04:41.98,Default,,0000,0000,0000,,But chiral molecules\Nare absolutely everywhere.
Dialogue: 0,0:04:42.00,0:04:44.98,Default,,0000,0000,0000,,Phenomena as separate as optical rotation,
Dialogue: 0,0:04:45.00,0:04:46.98,Default,,0000,0000,0000,,Screwing together furniture,
Dialogue: 0,0:04:47.00,0:04:48.98,Default,,0000,0000,0000,,and clapping your hands
Dialogue: 0,0:04:49.00,0:04:53.00,Default,,0000,0000,0000,,all involve this intriguing\Nspatial property.