Alcohols, Ethers, and Epoxides: Crash Course Organic Chemistry #24 - Free Educational videos for Students in K-12

Alcohols, Ethers, and Epoxides: Crash Course Organic Chemistry #24 - By Math and Science

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00:0-1	You can review content from crash course Organic Chemistry with
00:02	the crash course app available now for android and IOS
00:05	devices . Hi , I'm joking , Chakravarty and welcome
00:08	to Crash course Organic Chemistry . What do you think
00:10	of alcohol ? You probably think of alcoholic drinks like
00:13	beer , wine or spirits ? As we touched on
00:16	an episode 22 when we talked about elimination reactions .
00:19	The alcohol in all of these drinks is ethanol produced
00:23	during fermentation and while ethanol is toxic in larger quantities
00:27	, the amount in a few drinks just leaves you
00:29	feeling a bit tipsy , ethanol is only one member
00:32	of the alcohol family , though the alcohol with one
00:35	fewer carbon methanol can cause bigger problems . If you
00:38	drink it in our body , it's oxidized into formic
00:41	acid , which can damage the optic nerve , causing
00:44	blindness and even death . But alcohol's aren't all toxicity
00:48	and death . They can also serve a protective role
00:50	in hand sanitizers , which usually contain ethanol , propranolol
00:54	or isopropanol . Hand sanitizers affect the structure of proteins
00:58	, causing them to become misshapen or denatured . They
01:01	destroy the proteins that make up the outer shells of
01:04	viruses and bacteria killing them and preventing infections and inorganic
01:09	chemistry alcohols are useful building blocks . In this episode
01:13	we'll look at how we can use them as a
01:14	starting point to get to other oxygen containing organic compounds
01:18	, ethers up oxides and more . Yeah , yeah
01:31	. We've already seen a few ways to make alcohols
01:34	. Back in episode 16 , we saw how acid
01:36	catalyzed hydration of Calkins can add water across the double
01:40	bond market . Dickov's rule tells us that the proton
01:43	adds to the carbon in the double bond with the
01:45	most hydrogen is attached . We also saw that with
01:48	certain special re agents . The opposite happens , the
01:51	hydrogen ends up on the carbon in the double bond
01:53	with the fewest hydrogen is attached and we get what's
01:56	known as the anti Markov knockoff product . Another way
01:59	of making alcohols that we saw back in episode 20
02:01	is using substitution reactions . For example , mixing a
02:04	hallow al cane with sodium hydroxide will cause the hydroxyl
02:08	group to displace the Halide ion . We can also
02:10	create a dial , basically a double alcohol by using
02:14	an alkaline . Like we saw an episode 17 reacting
02:17	in alkaline with the oxidizing agent . Osmium tetroxide initially
02:21	produces an oz made Esther , which can then be
02:23	hydrolyzed by water to produce the dial . The hydroxyl
02:27	groups are added to the same side of the double
02:28	bond . So the product is what's known as a
02:30	sin dial . So , okay , we've clearly seen
02:33	lots of different ways to make alcohols . But what
02:36	about if we use alcohols in chemical reactions ? What
02:40	happens then ? Well , we've seen that hydroxide ions
02:43	are excellent nuclear files , but alcohol's aren't so nuclear
02:46	. Filic , their charges neutral and the oxygen and
02:49	hydroxyl group holds tightly onto its electron pair . However
02:53	, alcohols are weakly acidic compounds with a PK around
02:56	16 . So if we D . Protein eight and
02:58	alcohol , we make an Alcock side , the negatively
03:01	charged conjugate base , which is an excellent nuclear file
03:04	. Alcock sides can help us make a different oxygen
03:06	containing organic compounds , ethers which have an oxygen connected
03:10	to to alcohol or aromatic carbons . Let's start by
03:13	looking at a general model of the reaction which proceeds
03:16	by an sN two mechanism . The Alcock side displaces
03:19	the Halide ion , leaving us with an either to
03:22	get more specific . Here's the synthesis of diet either
03:25	which was used as a general anesthetic in the 18
03:27	hundreds before we figured out anesthetics that didn't make patients
03:31	vomit quite so much . We start with ethanol as
03:34	our alcohol and another re agent , plain old sodium
03:36	metal or sodium hydride , which is a negatively charged
03:39	hydrogen with a pair of electrons that can act as
03:42	a base . The sodium hydride can deep throat innate
03:44	ethanol generating and earth oxide ion . Then we add
03:48	the alcohol into the mix and the lone pair of
03:50	electrons on the oxygen attacks the carbon atom in bromo
03:54	ethane , booting out a bromide ion , informing di
03:56	ethyl ether . Great . So we've made in either
03:59	now what ? Well actually not a lot ethers are
04:03	incredibly stable compound so it's difficult to get them to
04:06	do much in terms of chemical reactions . The one
04:08	thing we can do besides using them as an old
04:10	timey anesthetic is breaking either back down using a strong
04:14	acid and a substitution reaction here , the strong acid
04:17	protein , it's or di ethyl ether . Then the
04:20	lone pair of electrons on the bromide ion attacks the
04:23	electrode positive carbon atom attached to the oxygen , breaking
04:26	the C . O bond . So we have our
04:28	starting compounds again . And alcohol lied and an alcohol
04:32	, if we've got a lot of extra strong acid
04:33	are alcohol can also be converted to an alcohol .
04:36	Hey lied through another substitution reaction with the bromide ion
04:39	. So we're left with two alcohol lights at the
04:41	end of this , either breakdown converting alcohols to alcohol
04:44	highlights is actually a really useful tool for chemists remember
04:48	that hydroxyl groups in alcohols are poor leaving groups because
04:51	the hydroxide ion is a strong base . So if
04:54	we can turn the hydroxyl group into a good leaving
04:57	group like a hell I'd we can make it more
04:59	useful for other reactions . There are three re agents
05:02	we can easily use to convert alcohols into alcohol ,
05:05	hal IEDs , hydrogen Halide , phosphorus , try bromide
05:08	and thiamine chloride . We just saw an example of
05:10	a hydrogen Halide , specifically hydroponic acid , pro donating
05:14	hydroxyl groups to break down a diagonal ether . And
05:17	here's the basic model of this reaction with an alcohol
05:20	. The second option is using phosphorus try bromide here
05:24	, the electron pair on the oxygen of our alcohol
05:26	attacks the phosphorus atom , kicking out a bromide ion
05:30	. The bromide iron can then act as a nuclear
05:32	file and get a little bit of revenge . It
05:34	swoops around and kicks out the oxygen that just bonded
05:37	to the phosphorus , which is a good leaving group
05:39	. That leading group can then go on to react
05:41	with two other alcohol molecules going through the same steps
05:44	. So overall one mole of phosphorus tribe Rome .
05:47	I can convert three moles of an alcohol into three
05:50	moles of an alcohol bromide . The final option for
05:52	making an alcoholic allied from an alcohol , uses these
05:55	vinyl chloride and only works for primary and secondary alcohol
05:58	. First the alcohol and vinyl chloride react to form
06:01	an ox ammonium ion intermediate . The chloride ion then
06:04	attacks the carbon next to the oxygen , giving the
06:07	electrons back to oxygen and neutralizing it . And there
06:11	we have it . The alcohol chloride , most of
06:13	the alcohol to alcohol highlighted stuff . We just did
06:15	involve SN two mechanisms which flips the stereo chemistry at
06:19	Kyle carbons . So if we add a nuclear file
06:22	and sN two reaction later , we'll get double inversion
06:25	of stereo chemistry and we're back to the stereo chemistry
06:28	of our starting alcohol . Now if you're stuck with
06:30	an alcohol , want to make it more reactive and
06:33	don't want to go with the highlight leaving group .
06:35	There are other options . For instance , you could
06:38	use Tosel chloride or measles chloride to turn alcohols into
06:41	Tosel . It's or missile . It's in these reactions
06:44	. The stereo chemistry at the carbon attached to the
06:46	hydroxyl group stays the same so later if we add
06:49	a nuclear file and doing snt reaction on our missile
06:52	, it the stereo chemistry of the starting alcohol is
06:55	inverted . This isn't to say that making an alkali
06:57	Halide is better than making them easily or vice versa
07:00	. A lot of organic chemistry involves multi step reactions
07:03	and carefully controlling products . So it's useful to know
07:06	reactions that can do subtly different things . Remember ,
07:10	the stereo chemistry can have huge differences on the function
07:12	of molecules from smell to toxicity . We also just
07:16	tweak the structure of alcohol is a bit to make
07:18	a pox sides which are essentially cyclic ethers where the
07:21	oxygen forms a three adam ring with two carbon atoms
07:24	. If a pox side sound familiar , that's because
07:27	we've seen how to make them from al keane's already
07:29	. But we can also make them from hala hydrants
07:32	, compounds containing a Halide and a hydroxyl group on
07:35	adjacent carbon atoms . Which we learn to make an
07:37	Episode 16 . We come across a pox sides in
07:40	epoxy glues where they react with a means to form
07:42	an adhesive polymer . A pox sides are also important
07:45	when it comes to organic synthesis because they're much more
07:48	reactive than the very stable ethers that we could only
07:51	break down with a strong acid up oxides have a
07:53	lot of ring strain so they open up pretty easily
07:56	. We can actually break open the ring in two
07:58	ways to form two different products through an acid catalyzed
08:01	reaction or a base catalyzed reaction . The acid catalyzed
08:04	reaction , which we also met an episode 16 is
08:07	an S . N . One like reaction involving are
08:09	up , oxide and acid and a nuclear file .
08:12	Having an acid means we have a bunch of protons
08:14	floating around . So first the oxygen in the ip
08:17	oxide gets protein ated . Then we have a knack
08:19	sodium ion with a positive charge which has residents with
08:22	two carbo cat ions . So the nuclear file attacks
08:25	the more substituted carbon . The one with better stabilized
08:28	carbo catalon character . Breaking open the ring . And
08:31	finally there's one more deep rooted nation to give the
08:34	final product . On the other hand , in the
08:36	base catalyzed reaction , there's nothing to protein eight .
08:39	The ip oxide . We've just got our up oxide
08:41	and our basic nuclear file . So the nuclear filic
08:44	attack comes first . The nuclear file will attack the
08:46	least substituted carbon , triggering an SN . Two reaction
08:49	in breaking open the ring . Then we can add
08:52	in some acid in a second step , and the
08:54	negatively charged oxygen grabs a proton , forming the final
08:57	product . Like I mentioned , the products of acid
08:59	catalyzed and base catalysed reactions are different because these two
09:03	reactions can have different ratios selectivity . We don't have
09:06	to think about it too much now , but this
09:07	will be useful for multi step reactions to Okay ,
09:10	we've just got one final set of alcohol reactions to
09:13	cover oxidation . Remember from episode 17 , we can
09:17	define oxidation as the loss of electrons . Remember leo
09:21	the lion says ger and we can also define oxidation
09:24	in organic chemistry as the loss of carbon hydrogen bonds
09:27	or gain of carbon oxygen bonds . Alcohols can be
09:30	oxidized using chronic acid and the products we get are
09:33	determined by the type of alcohol . We're starting with
09:36	primary alcohols initially oxidized to formaldehyde . But because chronic
09:40	acid is a strong oxidizing agent , it will keep
09:43	on going oxidizing the alga hide to a carb oxalic
09:45	acid . If you're starting with a secondary alcohol ,
09:48	you'll end up with a key tone after the oxidation
09:50	reaction . But if you've got a tertiary alcohol ,
09:53	you're out of luck . Even a strong oxidizing agent
09:56	won't do the job . Let's look at part of
09:58	the mechanism of alcohol oxidation . To see why .
10:01	As for example , let's use benzoyl alcohol , which
10:03	we can see from the structure is a primary alcohol
10:06	. This can be oxidized to Ben's Aldo hide the
10:09	molecule that gives almonds their characteristic smell . And Ben's
10:12	Aldo hi , can be oxidized to Ben's OIC acid
10:14	, which is used as a food preservative in the
10:16	mechanism here , you can see that the oxidation reaction
10:19	removes hydrogen atoms from the Benzel alcohol molecule , which
10:23	lines up with our definition of oxidation for organic molecules
10:26	specifically are starting molecule loses two hydrogen atoms to make
10:30	the alga hide one from the hydroxyl group and the
10:32	other from the adjacent carbon . So we can see
10:34	why tertiary alcohols just won't oxidized . They don't have
10:38	any hydrogen is attached to the carbon with the hydroxyl
10:40	group , so they certainly can't lose two of them
10:43	. Meanwhile , the chromium is reduced from chromium six
10:46	, which is orange in solution to chromium three ,
10:48	which is green . This gives us a handy color
10:50	change to indicate that oxidation of our alcohol has taken
10:53	place . If oxidation hasn't taken place , we won't
10:57	see a color change easy . Is that okay ?
10:59	But what if you've got a primary alcohol , you
11:01	don't want to oxidize all the way to a carb
11:04	oxalic acid . This is where weaker oxidizing agents come
11:07	in instead of a very strong chronic acid . We
11:10	can use something milder like pure titanium claro , chrome
11:12	eight NPR dini um die chrome eight to stop at
11:15	an AL . To hide . The downside of all
11:16	these oxidizing regions we've looked at is that they contain
11:19	chromium . It's good for that handy color change I
11:21	mentioned . But chromium compounds like chronic acid and bicarbonate
11:25	salts are toxic carcinogenic and corrosive . In other words
11:29	not great to be using regularly but there are some
11:32	safer mild oxidants that can be used instead . Such
11:34	as desk martin Paride in in or D . M
11:37	. P . So it's safe to say that alcohols
11:39	are way more than just beer and wine . They're
11:42	involved in lots of important reactions and make compounds with
11:45	specific reactivity , stereo chemistry and re geochemistry . We'll
11:49	be seeing plenty more of them in future episodes in
11:52	this episode we reviewed the reactions we know to form
11:54	alcohols . Looked at substitution reactions that can make alcohol
11:58	into better leaving groups . Learned how to open up
12:01	oxides , radio selectively and oxidized alcohols to Aldo hides
12:05	or carb oxalic acids with different re agents in the
12:07	next episode will take a break from adding more reactions
12:10	to our toolkit and apply some of what we learn
12:12	to a lab experiment . Until then , thanks for
12:14	watching this episode of Crash Course Organic Chemistry . If
12:17	you want to help keep all Crash Course free for
12:19	everybody forever , you can join our community on Patreon
12:25	Yeah .

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