Aldehyde and Ketone Reactions - Hydrates, Acetals, & Imines: Crash Course Organic Chemistry #29 - By CrashCourse
Transcript
00:0-1 | You can review content from Crash Course Organic Chemistry with | |
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00:05 | devices . Hi , I'm dave okay Chakravarty and welcome | |
00:08 | to Crash Course Organic Chemistry back in episode 27 we | |
00:12 | talked a lot about the synthesis of Aldo hides and | |
00:14 | key tones and now that we know the basics , | |
00:16 | we can build up to some more familiar chemical reactions | |
00:19 | involving the carbon Neil group , a carbon attached to | |
00:22 | an oxygen with a double bond stick with me for | |
00:24 | a second . I'm a huge fan of reality tv | |
00:27 | . I can't stop watching everything in the bravo cinematic | |
00:30 | universe and a common character . Trope though , it's | |
00:33 | definitely unhealthy and we should probably question why it's become | |
00:36 | so normalized is the overstressed mom who takes anti anxiety | |
00:40 | pills to make it through the day . The stereotype | |
00:43 | has been around since the 19 sixties and was even | |
00:45 | immortalized in the Rolling Stone song Mother's Little Helper . | |
00:48 | It's complicated because sedatives like Xanax or Valium can be | |
00:52 | prescribed as anti anxiety medication and really help people , | |
00:56 | but they have also been abused because our focus here | |
01:00 | is organic chemistry . In this episode , we'll learn | |
01:02 | what these sedatives all have in common . Carbonell chemistry | |
01:08 | . Mhm mm . Thanks to the polar ceo bond | |
01:18 | in a carbon steel group , the carbondale carbon has | |
01:21 | a partially positive charge . In episode 27 we talked | |
01:24 | about cyanide , a satellite and ions and the fast | |
01:27 | ammonium eyelids used in the video reaction attacking this partially | |
01:31 | positive carbon . These reactions extend the carbon chain allowing | |
01:35 | us to make bigger , more complicated molecules . And | |
01:38 | other nuclear files can also attack the carbon Neil group | |
01:41 | . In this episode will focus on addition reactions of | |
01:44 | oxygen and nitrogen based nuclear files . A simple oxygen | |
01:48 | based nuclear file that were already quite familiar with is | |
01:50 | water . If you mix water with an alga hide | |
01:52 | or ketone and equilibrium forms with the hydrate form called | |
01:56 | general dials or gem dials . The word germinal is | |
01:59 | similar to gemini's , one of several latin words describing | |
02:02 | twins . And in chemistry , germinal is used when | |
02:05 | we're talking about a molecule with two or more of | |
02:08 | the same functional group attached to a single atom . | |
02:11 | Usually this equilibrium favors the alga hide or ketone because | |
02:14 | of inductive effects groups like metals or ethel's are electron | |
02:18 | releasing , meaning they push electrons towards the partially positive | |
02:22 | carbon and carbon Neil and stabilize it . There are | |
02:25 | examples that break this pattern though like the smallest Aldo | |
02:28 | hide formaldehyde , mixing water with formaldehyde produces a solution | |
02:32 | called formalin formal and helped preserve tissues from decay . | |
02:36 | So it's what scientists use to preserve tissue specimens in | |
02:39 | jars and not just scientists artists to Damien Hirst exhibited | |
02:44 | a whole preserve tiger shark . Thinking about inductive effects | |
02:47 | . The hydrogen atoms on formaldehyde don't do much to | |
02:50 | stabilize the partial positive charge on the carbon . So | |
02:54 | the equilibrium in a formal in solution very much favors | |
02:57 | the gem dial , not the alga hide . We | |
02:59 | can also make stable gem dials by substituting Aldo hides | |
03:02 | with strong electron withdrawing groups like chlorine , which destabilized | |
03:06 | the partial positive charge on the carbondale carbon . For | |
03:09 | example , if we mix to to to try clara | |
03:12 | a settled to hide with water , it forms chloral | |
03:15 | hydrate , which was given as a sedative in asylums | |
03:17 | and much abused in the late 19th century chloral hydrate | |
03:21 | in ethanol is colloquially known as knockout drops or a | |
03:24 | mickey finn , which is probably named after a Chicago | |
03:27 | bartender who gained infamy after using this mixture to incapacitate | |
03:32 | and steal from some of his customers . Big yikes | |
03:35 | . Now we can also react carbonell compounds with other | |
03:38 | oxygen based nuclear files like alcohol groups . When a | |
03:41 | single alcohol group adds to an AL to hide , | |
03:44 | we get a heavy a settle . The name comes | |
03:46 | from the greek word hemi , meaning half because only | |
03:49 | one alcohol is added . There are also full blown | |
03:52 | as tools that we'll talk about in a bit which | |
03:54 | have two alcohol groups added . Hermia settles are generally | |
03:57 | less stable than their Aldo hide equivalents . So the | |
04:00 | equilibrium favors the alga hide as it does with many | |
04:03 | gem dials , sugars and other molecules that can form | |
04:06 | inter molecular and sick leukemia settles can be exceptions . | |
04:10 | In a quick solution , glucose rapidly inter converts between | |
04:14 | its straight chain and cyclic forms when one of its | |
04:16 | alcohol groups attacks it's carbondale carbon . Since the carbondale | |
04:20 | group in glucose has a traditional planner geometry and our | |
04:23 | intra molecular hydroxy nuclear file can attack from either side | |
04:27 | are hemi . A subtle products are to die hysteria | |
04:30 | MERS , but we can get even more specific in | |
04:33 | what we call them . The sugar world actually has | |
04:35 | lots of special vocabulary . The hemi , a subtle | |
04:38 | carbon of a sugar is called the an americ carbon | |
04:40 | . So these two products are more precisely called an | |
04:43 | Immers , one labeled alpha and one labeled beta . | |
04:46 | In the beta animal , these groups end up on | |
04:48 | the same side and in the alpha animal , these | |
04:50 | groups are opposite . The beta animal of glucose is | |
04:53 | actually favored in water because similar to cycle heck saying | |
04:57 | it can adopt a comfy , stable chair confirmation . | |
05:00 | And all the groups are equatorial , which also helps | |
05:03 | reduce derek hindrance and increased stability that covers the basics | |
05:07 | of hermia settles . So now let's take off that | |
05:09 | heavy prefects and make a settles which form when two | |
05:12 | alcohol groups add to an AL to hide or a | |
05:15 | key tone . These reactions are acid catalyst . So | |
05:18 | the three players are a carbon steel group in alcohol | |
05:21 | and acid . Looking at the summary reaction , we | |
05:23 | can see that we need to add two molecules of | |
05:25 | methanol to the carbonell carbon to form the product . | |
05:29 | So let's puzzle through the mechanism . If we added | |
05:31 | methanol as a first step , that would give us | |
05:34 | a negative charge , which we can't have in an | |
05:36 | acid . Okay , so we've got to try something | |
05:39 | else to start in acidic conditions . We have protons | |
05:42 | and there's a lone pair on the carbon oxygen . | |
05:45 | So what if that loan paragraph two proton from an | |
05:48 | ox ammonium ion ? We have a positive charge , | |
05:51 | which is totally fine in our acid . Even though | |
05:54 | this works as a first step , the oxygen isn't | |
05:56 | happy about this whole positive charge situation . It draws | |
06:00 | a pair of electrons in the carbon oxygen double bonds | |
06:03 | towards itself , making the carbondale carbon very electra positive | |
06:06 | and prone to nuclear filic attack . Looking at our | |
06:09 | product , we want to add meth oxy groups to | |
06:11 | that carbon . So that means the nuclear file we | |
06:14 | choose for this attack is our alcohol . Specifically a | |
06:16 | lone pair on the oxygen of one of the alcohol | |
06:19 | molecules attacks the carbon carbon and adds a methanol . | |
06:23 | We've still got a positive charge on the molecule though | |
06:25 | , so this isn't stable enough to be an end | |
06:27 | product . We've got to make our way to a | |
06:29 | neutral molecules somehow . Remember , we've got plenty of | |
06:32 | alcohol molecules floating around with two lone pairs on their | |
06:35 | oxygen atoms . So one of those alcohols can grab | |
06:38 | the spare proton on our molecule , leaving us with | |
06:40 | an O . H . And an O . R | |
06:42 | . Group attached to the what was the carbon Neil | |
06:44 | carbon ? Now we have a hemi a subtle , | |
06:46 | so we're getting closer but to have a full blown | |
06:50 | a subtle we need another myth oxi group . Instead | |
06:52 | of that . Ohh . In our acidic conditions , | |
06:54 | we can get rid of the O . H . | |
06:56 | By making it a good leaving group that ohh grabs | |
06:58 | a proton from a pro donated molecule of methanol . | |
07:01 | We might be tempted to have another molecule of methanol | |
07:04 | attack and kick off water at this point , but | |
07:06 | that would be like S and two at a tertiary | |
07:08 | carbon , which doesn't work because remember there's not enough | |
07:12 | room for the backside attack . Instead , we get | |
07:15 | a little help from the adjacent oxygen . A lone | |
07:18 | pair of electrons on the oxygen of the newly attached | |
07:21 | alcohol group help push out water , forming an arc | |
07:24 | sodium ion and a molecule that's not that different from | |
07:27 | where we started except now , instead of a protein | |
07:30 | ated carbondale , we have a carbon feel attached to | |
07:32 | a metal group on oxygen . The similarity is important | |
07:35 | to notice because we can basically do the same set | |
07:38 | of moves again . A nuclear filic attack from another | |
07:41 | alcohol molecule followed by D pronation . And we get | |
07:44 | our a settle with two meth oxy groups . We're | |
07:46 | done . That was a lot . So let's review | |
07:49 | all of the steps of our reaction mechanism with the | |
07:51 | arrow pushing in these acidic conditions . This process is | |
07:55 | reversible heat and to settle with water and acid and | |
07:58 | boom back to the ketone or Aldo hide . But | |
08:02 | if acid isn't present a settles are really stable once | |
08:05 | they're formed , in fact , they won't even react | |
08:08 | with really strong nuclear files like carbon ions . Societal | |
08:10 | formation is an important strategy for controlling the reactivity of | |
08:14 | Aldo hides in ketones in multi step reactions . So | |
08:18 | we'll come back to this when we talk about protecting | |
08:20 | groups in a later episode , for now , we'll | |
08:22 | move on to another similar reaction involving the formations of | |
08:26 | means in china means it means our molecules with carbon | |
08:29 | nitrogen double bonds and china means contain a carbon carbon | |
08:32 | double bond next to an amine and al keen . | |
08:35 | Plus in a mean , it means come from a | |
08:37 | carbon Neil and a primary amine , while china means | |
08:41 | come from secondary amines . One way to remember . | |
08:43 | The difference is to notice that the words mean and | |
08:46 | a mean are the same except for one letter . | |
08:49 | So it means come from primary amines . Inamine , | |
08:52 | on the other hand , has two extra letters . | |
08:55 | So china means come from secondary amines . The mechanism | |
08:58 | for women formation is similar to a subtle formation with | |
09:02 | three main players . A carbon you'll group a primary | |
09:05 | amine an acidic conditions . Once again , there's a | |
09:08 | lone pair on the carbon . He'll oxygen that can | |
09:10 | grab a proton . Then the nuclear file , which | |
09:13 | is the nitrogen . In the I mean this time | |
09:15 | can attack the carbon atom of the protein ated carbonell | |
09:18 | group . The pi electrons in the carbon oxygen double | |
09:20 | bond neutralized the axe , ammonium ion and our intermediate | |
09:23 | molecule has an amine and an O . H . | |
09:26 | On the What was the carbonell carbon ? As in | |
09:28 | a subtle formation , oxygen gets protein ated the nitrogen | |
09:32 | lone pair forms a carbon nitrogen double bond and water | |
09:35 | is eliminated . That leaves us with an a mini | |
09:37 | um ion , which is any molecule with a positive | |
09:40 | charge on the double bond in nitrogen . After a | |
09:43 | deep pronation , we get an amine . However , | |
09:46 | if we're making an Inamine and start with a carbon | |
09:48 | steel group , a secondary amine and a set of | |
09:50 | conditions , we can't do this final discrimination step . | |
09:54 | The nitrogen has to our groups . Instead of a | |
09:56 | hydrogen , we can just kick out . So instead | |
09:59 | the final step of the mechanism is deep resonating the | |
10:01 | carbon adjacent to our mini um ion giving us an | |
10:04 | enemy . I mean this is a great moment to | |
10:06 | mention a compound called nine hydrant , which is used | |
10:09 | in chromatography to identify amino acids and forensics , to | |
10:12 | view fingerprints specifically nin hydrant detects the amines present in | |
10:16 | the amino acids and proteins left behind by our fingerprints | |
10:20 | . When it reacts with the amino acids , a | |
10:22 | deep blue purple color appears called romans purple . This | |
10:26 | is actually an immune forming reaction that occurs on the | |
10:29 | keto form of nine hydrant . And the mechanism is | |
10:33 | fairly straightforward that central carbonell carbon in the five member | |
10:37 | ID ring , smushed between all those carbonell groups has | |
10:39 | a big partially positive charge . So it's really attractive | |
10:44 | to nuclear files as a result , when Inamine turns | |
10:46 | up , say from the oily residue left by a | |
10:49 | finger , the lone pair on the nitrogen attacks the | |
10:52 | central carbon . Then the nine hydrant is dehydrated and | |
10:55 | we form an enemy in the next few steps of | |
10:58 | this mechanism are beyond the scope of this episode . | |
11:00 | But basically another molecule of nine hydrogen reacts and the | |
11:04 | two molecules link up through the nitrogen atom . This | |
11:07 | compound is responsible for that pretty purple color and successful | |
11:11 | fingerprints sleuthing to continue linking our carbonell chemistry to real | |
11:14 | world applications . We can also look at the anti | |
11:16 | anxiety medicine that stereotype of dramatic tv . We talked | |
11:21 | about Valium to start , which is a brand name | |
11:23 | for days . A pan , the chemist Leo Sternbach | |
11:25 | and has gifted technician barrel Kapil discovered the first of | |
11:28 | this family of compounds by accident in the mid 19 | |
11:31 | fifties called Claudia's Up oxide . Capital had been screening | |
11:34 | potential muscle relaxants for seven years when she found that | |
11:38 | this compound had anxiety reducing effects . A few years | |
11:41 | later , the discovery of diazePAM followed these drugs quickly | |
11:45 | became popular because they reduce anxiety and tension without the | |
11:48 | knockout effect of something like chloral hydrate . These days | |
11:51 | , doctors are increasingly cautious about prescribing them because they're | |
11:54 | habit forming cause respiratory depression and long term use is | |
11:58 | associated with cognitive impairment . However , despite its complicated | |
12:01 | medical history , diazePAM is a useful example for carbonell | |
12:05 | chemistry . Let's focus on one part of its synthesis | |
12:08 | involving the top bit of the molecule with a clear | |
12:10 | acetate . A likely mechanism starts with the carbon attached | |
12:13 | to the chlorine being attacked by nuclear filic ammonia , | |
12:16 | replacing the chlorine with N H two . In an | |
12:18 | SN two reaction . After that , you'll notice we | |
12:21 | have an amine , nice and close to a carbon | |
12:23 | Neil group . That carbon Neil group is irresistible to | |
12:26 | the nuclear filic nitrogen . And it attacks forming the | |
12:29 | I mean that is part of diazePAM . This inter | |
12:31 | molecular reaction closes the seven member ID ring . That's | |
12:34 | a signature part of this family of medicines . Overall | |
12:37 | in this episode , we've learned that Aldo hides can | |
12:40 | form hydrates and water and formula is a particularly important | |
12:44 | example . The two animals of the hemi astral form | |
12:47 | of glucose are connected by a reversible reaction between al | |
12:50 | to hide and alcohol groups . A settles can be | |
12:53 | a useful way to protect carbon steel groups in longer | |
12:55 | sin theses and it means and china means can be | |
12:58 | formed from Aldo hides and ketones . That's it for | |
13:01 | Aldo hides in key tones for now . But we | |
13:03 | definitely haven't seen the end of these important functional groups | |
13:07 | . They'll pop back up here and there . Next | |
13:09 | episode will explore another kind of carbon heel containing chemical | |
13:13 | the car bucks silic acid . Until then , thanks | |
13:15 | for watching this episode of Crash Course Organic Chemistry . | |
13:18 | If you want to help keep all crash course free | |
13:20 | for everybody forever , you can join our community on | |
13:23 | Patreon . |
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Aldehyde and Ketone Reactions - Hydrates, Acetals, & Imines: Crash Course Organic Chemistry #29 is a free educational video by CrashCourse.
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