Alkene Redox Reactions: Crash Course Organic Chemistry #17 - Free Educational videos for Students in K-12

Alkene Redox Reactions: Crash Course Organic Chemistry #17 - By CrashCourse

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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 Dave okay Chakravarty and welcome
00:08	to Crash course organic chemistry oxidation , reduction reactions ,
00:11	also known as redox reactions are all around us from
00:16	charging cell phone to avocados turning brown and they happen
00:19	inside of us to redox reactions . Let us strip
00:22	electrons off the food we eat and add them onto
00:25	the oxygen we breathe to give us the energy we
00:27	need to survive . Speaking of electrons in Crash course
00:30	general chemistry we defined oxidation as the loss of electrons
00:34	and reduction as the gain of electrons . Or as
00:37	I remember it , leo the lion says Gert losing
00:40	electrons , oxidation and gaining electrons is reduction . These
00:43	rules are true for organic molecules but it can sometimes
00:46	be easier to track the number of carbon oxygen bonds
00:49	we gain or lose . For example , the molecule
00:51	methane can be oxidized by replacing carbon hydrogen bonds with
00:55	carbon oxygen bonds until we get carbon dioxide , the
00:58	most oxidized form of a single carbon atoms . On
01:01	the flip side , carbon dioxide can be reduced by
01:04	replacing oxygen atoms or oxygen carbon bonds with hydrogen atoms
01:08	. So we can also define oxidation is gaining bonds
01:11	to oxygen and reduction as losing carbon oxygen bonds .
01:15	In this episode , we'll consider the oxidation and reduction
01:18	reactions of all kinds and see what types of oxygen
01:20	containing compounds we can make from Calkins . Yeah ,
01:34	Oxidizing agents are molecules that oxidize organic compounds . They
01:38	accept electrons from the organic compound and in the process
01:41	three agents are reduced . Oxidizing agents are usually the
01:44	culprits behind multiple carbon oxygen bonds forming from an alkaline
01:48	. We'll see two types of oxidizing agents in this
01:50	episode , ones with oxygen oxygen bonds and ones with
01:53	metal oxygen bonds . Like we worked on last episode
01:56	, a handy way to see patterns and predict products
01:58	in addition reactions is by asking three key questions are
02:02	three parts secret handshake question number one , what are
02:05	we adding across the double bond question number two ,
02:08	where will the groups add on an asymmetrical molecule in
02:12	general ? This question is asking about radio selectivity market
02:15	because rule is an example of regio selectivity and question
02:19	number three , what is the expected stereo chemistry of
02:21	the added groups ? If they are added to the
02:23	same face of the alkaline , it's Sin edition or
02:26	if they're added to opposite faces , it's called Anti
02:29	Edition in this episode , we'll look at these questions
02:31	in the context of reactions that oxidize are alkaline friends
02:34	. We saw an example of an oxidizing agent at
02:36	the end of episode 16 with hydro operation oxidation .
02:40	When hydrogen peroxide replace the boron atom we added to
02:43	the al Qaim , we can also use peroxide to
02:45	perform a reaction called iP oxidation and up oxide is
02:48	a three member ID ring with an oxygen and we
02:50	can make things from Calkins . So question number one
02:53	is pretty straightforward approximation , adds one oxygen molecule across
02:58	both atoms of the double bond . Usually we do
03:00	approximation by reacting an alkaline with EM CPB , a
03:03	medical or a peroxide Ben's OIC acid . You might
03:06	see this reaction written out in a simplified way like
03:09	this , but if you draw everything out , you
03:12	can see how EM CPB A transfers one of its
03:14	oxygen atoms in the process . To answer our other
03:17	questions , we need to look at the reaction mechanism
03:20	like hydro operation . We have another concerted reaction that
03:23	happens all at once . So there's a lot of
03:25	electron pushing to help us get to the transition state
03:28	. In fact , if you can get this mechanism
03:30	down , you'll be doing great . This reaction has
03:33	some of the most complex aero pushing we'll see in
03:35	a one step organic reaction basically the falcons double bond
03:39	forms a strained bridge with the blue oxygen . At
03:42	the same time . The other bonds break on EM
03:44	CPB A . I'd like to start with the double
03:46	bonded oxygen in EM CPB A and attack the proton
03:50	. Then I can use the electrons from the oxygen
03:52	hydrogen bond to attack the alki . The alkaline attacks
03:55	back and the bonds of the blue oxygen that breaks
03:58	forms a new carbon Neil . And the transition state
04:01	looks like this because we're only adding one atom and
04:04	its bridge . The answer to question two is it
04:06	doesn't matter essentially the same group is added to each
04:10	side and because everything is all attached at once in
04:12	a concerted reaction . If we look at the stereo
04:15	chemistry , we always have a sin edition . That's
04:17	our answer to question three . The oxygen bridge can
04:20	form on either side of the double bond . So
04:22	we get to different in anti MERS as products and
04:24	or ischemic mixture , which as you might remember ,
04:27	means equal amounts of each one . Overall approximation has
04:30	a pretty straightforward combo . We can sum it up
04:33	with another card , so now we know how to
04:36	make it up oxide , which is a fun little
04:38	ring shape . Earlier in this series , we looked
04:40	at the bond energy of cyclo propane and learned that
04:42	three member ID rings have a lot of strain so
04:45	they're fairly unstable and instability means the chance for some
04:49	exciting chemical reactions . Specifically , we can use up
04:52	oxides as a gateway to anti die hydroxy elation .
04:55	A name that hints at the stereo chemistry of this
04:58	reaction . Spoiler alert , it's going to be anti
05:00	edition . This name also hints at what we're going
05:03	to end up with two hydroxyl groups also known as
05:06	alcohol groups . Yes , hydroxyl and alcohol are interchangeable
05:11	in case . Organic chemistry nomenclature wasn't tricky enough .
05:14	The anti die hydroxy elation reaction happens the same way
05:16	for both an anti members of an ip oxide .
05:18	So we'll look at just one stereo . I seem
05:20	to remember a strong acid in water forms hydro Nehemiah
05:23	. So when we add a quiz hydrochloric acid to
05:26	an ip oxide , the nuclear filic oxygen will attack
05:29	our electro filic hydro Nehemiah , which makes a positively
05:32	charged oxo Nehemiah . This next step is where it
05:35	gets fun . A water molecule will swoop in as
05:37	a nuclear file in an anti attack and open the
05:40	app oxide . In this particular case , the water
05:42	molecule can attack either of the a pox I'd carbons
05:45	. The final step of a pox side opening is
05:47	that typical 12 punch pattern that happens under acidic conditions
05:51	. A water molecule ads first and the ac sodium
05:54	ion we get is deep resonated by a second molecule
05:57	of water . This makes the systemic mixture of 44
06:00	dimethyl cyclo hexane one to dial and that's it .
06:03	Here's our three step summary of anti die hydroxy elation
06:07	. The overall effect of the anti die hydroxy elation
06:10	process is the addition of two alcohol groups on opposite
06:13	sides of the substrate . But if we wanted to
06:15	add them to the same side , we need a
06:17	totally different reaction logically called Cindy hydroxy elation . And
06:21	we actually have two options for oxidizing agents here ,
06:24	like fraternal twins . They're related but have some distinguishing
06:27	features . One metal catalyst is Oz me um tetroxide
06:30	, which is a wonderful source of oxygen but also
06:33	super toxic . It's safer to use less of it
06:36	so we can add other oxidizing agents , Leichter ,
06:38	bugle peroxide or end metal morphine and oxide , also
06:42	known as an M . O . Into the reaction
06:44	. Nomo helps remake osmium tetroxide over the reaction and
06:48	lets us more safely use a catalytic amount of the
06:50	toxic metal . The first step in this reaction is
06:53	the formation of an oz made Esther , which is
06:55	why our hydroxyl groups end up . Sin the Osmium
06:58	regent approaches the double bond from one face . In
07:01	the reduction step , the sodium by cell fight bonds
07:03	to the Osmond Esther and helps it break apart in
07:05	water . If we use osmium tetroxide with nemo ,
07:08	the animo does two things . It helps break up
07:11	the Osmond Esther and gives up one of its oxygen's
07:14	to regenerate osmium tetroxide , making the reaction catalytic in
07:18	Oz me . Um The nitty gritty of these reactions
07:20	is inorganic chemistry and a little beyond the scope of
07:22	this series . What's most important for this one is
07:25	which re agents to use for Cindy hydroxy elation and
07:28	generally why they work so with that in mind .
07:31	The other twin reaction happens in a similar way .
07:35	The metal catalyst involved in the first oxidation step is
07:38	potassium permanganate . And that second step needs cold basic
07:41	conditions like sodium hydroxide floating around in an icy cold
07:44	solution . And here's our card to sum up Cindy
07:47	Hyde rocks elation up until this point we've been adding
07:50	alcohol groups to falcons which is all fine and good
07:53	. But it lacks some drama . Sure . All
07:56	chemical reactions are cool in their own unique ways .
07:59	But so far we've left our carbon chains intact .
08:01	What about something that blasts the molecule into smaller pieces
08:05	. Entropy turns out we can oxidize an alkaline and
08:07	break the double bond completely . Using a reaction called
08:10	those analysis , the name comes from our main region
08:13	ozone and license , which is greek for breaking something
08:16	down to understand how this happens . Let's look at
08:19	the reaction mechanism . First step is R Tolkien reacting
08:21	with ozone so it adds across the double bond .
08:24	This makes an intermediate , which then breaks apart and
08:27	rearranges into a molecule called ozone . I after we've
08:30	gotten ozone I . The next step is a quick
08:32	reduction reaction by adding D . M . S .
08:34	Or zinc and acid . The referees that break up
08:36	the reactant and our products are two different molecules each
08:40	with the carbon Neil group . Now these products might
08:42	be a little hard to visualize but we can think
08:44	of those analysis as a pair of oxidizing scissors that
08:47	snips the double bond in half while adding a double
08:49	bonded oxygen to each side . On paper . I
08:52	draw an alkaline and pencil . Use an eraser to
08:55	snip the double bond in the center and then add
08:57	in oxygen caps to both double bonded ends . Since
09:00	for splitting the double bond in half an oz analysis
09:02	, we don't need a no card . We don't
09:04	need to worry about stereo chemistry and re geochemistry .
09:07	Now we know lots of ways to oxidize Calkins and
09:09	we also need to learn how to reduce them ,
09:12	adding hydrogen across the double bond is called hydrogenation and
09:16	makes an al caine . However , the activation needed
09:18	to get the party started is really high because other
09:21	than the double bond , there aren't really any reactive
09:24	sites in the alkaline or molecular hydrogen . They're pretty
09:27	stable and boring as far as reactions go . So
09:30	, to help a hydrogenation reaction along , we need
09:33	a catalyst to lower the activation energy , usually a
09:36	metal like platinum or palladium first the hydrogen forms a
09:39	complex with the surface of the metal . The alcan
09:41	approaches the metal hydrogen complex and hydrogen that's added with
09:45	its electrons across the double bond , the alkaline gains
09:48	electrons so it's reduced and the metal surface makes the
09:51	hydrogen zad to one face a sin edition . Here's
09:55	our hydrogenation note card . In the past few episodes
09:58	, we've talked about a lot of different reactions involving
10:01	al caine's building intuition about the products along the way
10:04	. But let's face it in organic chemistry , we
10:07	need tons of practice . One way of practicing is
10:09	filling in a wheel of chemical reactions to see how
10:12	they're all connected , basically taping all our reaction mechanisms
10:15	together into one big map of the island of al
10:18	keane's . You can pause the screen here if you
10:20	want to take notes , here's the reaction wheel .
10:22	Our team drew up with one metal cyclo hex one
10:25	in in the centre . Look at all we've learned
10:27	in the past few episodes alone and there's still so
10:30	many more exciting things to come . But in this
10:32	episode we learned about oxidation , the addition of oxygen
10:35	and reduction , the addition of hydrogen in relation to
10:38	organic molecules , added two alcohol groups to an AL
10:42	king , both sin and anti . And used those
10:45	analysis to cleave a double bond . All our reaction
10:47	knowledge will keep building and we'll even see some familiar
10:50	regents next time when we explore reduction reactions with all
10:53	kinds . Thanks for watching this episode of Crash Course
10:55	Organic Chemistry . If you want to help keep all
10:58	Crash Course free for everybody forever , you can join
11:01	our community on Patreon . Mhm .

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