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Lecture 7: Conversion of Alcohols to Alkyl Halides

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are so we were talking about dehydration last time they and the mechanism depends on whether we have a primary secondary and tertiary because we have a primary alcohol we didn't the 2 mechanism if we have a secondary or tertiary we get 21 mechanism alright so that's where we left off last time is Greater reaction corresponds to the ease in which the Carver Academy is for all day women actually cost was a common currency form so does that make sense the tertiary is going to be the fastest OK so here's typical conditions I do not want you to memorize these conditions of trying to just give you of comparisons here so tertiary alcohol I hundreds of 50 what's didn't do our I did not break
your heart said please and they did it by members of the senator all the time and
that is the more common the it said it to that and that where the 2 were Formula One primary look he is not quite the case so I think here where did it all that's a was a of friend of me the only thing that where it is 1 the EU Strong into bowl face at the time of the year and the whole 1 that would needed always here In case it is not available the that that the I'm involved in forcing 2 editions goes by because primary can enter to stable are too unstable alright so and then watched as label this because when you come back and look at this stage you can think of do I have to memorize that typical reaction conditions don't memorize and so we are ready answer the question why is the primary our Hollymead forcing conditions and that's because that leads to the 2 reaction requires a strong base H S O 4 minus it is a very weak pace right so was so you your book is going to have some examples of of the elimination of about primary alkyl here like I don't want you to do it so I'm gonna say on adults to
dehydration as of a primary alcohol alternative at the end of this chapter what is the last stage of this chapter in Europe European book here was the last page alternative on page 1 very last Wednesday on page 47 OK and what's going to happen is on I teach the honors in majors lab we've already done elimination you guys are going to do the same experiment a week 5 wearing a find is that you don't get a good result from the primary alcohol so all this will make more sense when you do that expert I don't want you doing dehydration of a primary alcohol and any my task I know that this sapling I signed that Smith has questions using it I don't want you to use an annual you'll see more why that is when we get to Chapter 5 are exterior demagogue ,comma the 1 dehydration is the same as history ,comma ultimately 1 elimination but now killed alliance sidestepped said products which can be a mixture of Sisson trends mixture assistant trainer and somewhere with more of the isomer with the bulkier groups on opposite sides 4 of the isomer with the groups what opposite sides alright so just as we would expect and I would introduce something you hear about Carver battalions that we didn't tell you before this is something that was actually happening behind the scenes in Chapter 7 and Chapter III didn't mention it to you because we didn't feel like you were ready for it OK so that's how like you know when you have little kids you don't tell me there's tell me there's a Santa Claus and only a little older than they realize that there's no standard hostility now you're ready to know that cover patterns are not as well behaved as we have them painting a picture of them being well behaved 1 of the things that they do is they do arrangements so that means when you go back and you work problems in Chapter 7 and 8 there's actually extra products that were accounted for that actually do forming those reactions and and really anytime before macabre cattle and we can get rearrangements of 1st of all I want talked about what a rearrangement is and will talk about when we will see a rearrangements so it's not every single time but it's a lot of the time some dehydration 1 hand Hassan 1 reactions so were coming going this back to Chapter 7 and 8 unexpected products in which the nuclear file appears to have added to the wall ,comma the carbon skeletons have been rearranged and that's actually exactly what is happening here alright so here's a good example here this is dehydration meals dehydration we have age to us of 4 bank concentrated concentrate H 2 for and this is our expected product so if I have given you a little quiz before classes is the product that you would have written and this is the rearrange the unexpected product it turns out that in this case the rearrange product is actually the major problem so 1st of all we need to know how that's forming and then we need to know I am when when to expect that went not expect
that forex Serena looked at the file the secondary ,comma kind in this example so but in the 1st step we probably at the alcohol and is going to go directly to the 2nd step OK actually wants to show the 1st step over here just for fun I will use the abbreviated form of sulfuric acid and going appropriators this alcohol so when they go over here ground that hydrogen break the hydrogen oxygen bond and go down here so this is the 2nd step in the 2nd step since this is a primary alcohol that we've started with we're going to form a basis secondary alcohol would inform a secondary ,comma cat so on that so that's what happens in that cholesterol that secondary copper and and this is a this particular requiring is ideally situated to do arrangement so what is the rearrangement look like diminished change colors used to conceal better clear what's going to happen is that this magical is going to migrate over so the error should come from the middle of that bond there that carbon-carbon bond that can migrate with its pair of electrons is taking its electrons with fits and when it does that since it's taking both electrons with the it's now the carbonated just left as you know a macabre cabinets electron deficient that's because it took both of its electrons with so now the carbon on the right is no longer car recounting the carbon on the left is a cargo carrier and you can see that what we what we've ended up doing here is we've gone from a secondary cargo carrier to a true Sheri copycat and we know tertiary cover kinds more stable so where is the lottery arrangement is well worth making secondary Kirby if the secondary ,comma carrying can now rearranged to a tertiary it's going to happen there's nothing you can do to stop it OK so on and on on so it turns out that the elimination which is the 2nd step here will also debate a hydrogen can occur from both of these cover carriers so I'm going to draw both of them on the draw the first one unchanged before the rearrangement and this is the product that is the expected product In already have conjugate base of sulfuric acid command and mate remove that a hydrogen and then some for many wealthy OK so that can happen and that actually leads to the expected product
expected price but as we said we can also eliminate from this cargo carrier so this is a rearrange cargo category and what going expect for a major product is going to be and the most substituted all team so here's are powerful program here this one's beta this one's beta this 1 year's data right here which 1 are we going eliminated make him more substituted product anybody we need if we eliminate the hydrogen on were substituted carbon will get more substituted all came so that someone would eliminate based solely on must go and do that right here and have discussed around world grabbed that made a hydrogen anecdote down here and make a new carbon-carbon double bonds that leads to the rearrange all right questions on the rearrangement anybody's guess yes did a piece of the question is that we have 2 different Baylor hydrogen is here is going to depend on what I asked for on the test if I ask for all the products on that I don't want you to eliminate the other the other side type of the hydrogen bomb case of invite for the major products then denim and look for the 1 that's more substitute classes that OK so the metal migrants with its parent bombing electrons from the current adjacent to the electron deficient ,comma ,comma for which the group departs as a result becomes electron deficient because that nestles grabbing an extra hydrogen that actually belonged to that apartment taken with them this is ,comma won 2 medals shampoo rearrangements of public Major-General phenomena that occur when migration of a hydrogen manifold or other all out killed group so it's not just a cited another other outfielders leads to a more stable ,comma apparently season examples of each
once you Hydrogen Migration so it would be something like this notice what's different here we have a metal and therefore and a hydrogen In case so In this case we have a hydrogen likely so there's the new hydrogen right here curvature right so that would be a 1 2 on Hydrogen Migration Oriole also call it a 1 2 hydrogen shift that's the other thing and it moves them up from the neighboring province right onto the car Academy is out to migration this is 1 likely just saw so this is identical to the 1 just saw so we see that 1 of those methyl groups is going to end up on this problem here it's moved over and as we've gone from a secondary to a tertiary you could also have groups bigger than monthly didn't Ethel migrate in this case you can actually have on demand for migrating like this so that goes here and in again and we're going from a secondary ,comma :colon 2 0 short of course we can actually have some a carbon from the ring migrate this is a little trickier to see she will do 1 of these and discussion to give you a little practice here these are the hardest ones to predict the students 1 more time a redraw the part Karen and so this is going to look like is this is actually did this whole ring is gonna migrate we get a ring expansion that's a little mind-blowing it is but that's exactly what it looks like and can we know the six-member grain is more stable than a five-member so not only are we going from a secondary copycat that has an adjacent firing were going to a six-member bring tertiary Carver Cameron so that's really going to be on the verge of let's label all of these guys so this is a secondary cover Kateryna goes to a tertiary This is a secondary ,comma Catherine disclosed to a tertiary secondary cover :colon goes to a church secondary cover Karen goes to church and that's any commonly see this now I I often get the question Can is secondary ,comma can go to another secondary cargo it's about equal stability in real life yes but this is not real life here in my class it's going to go to a more stable ,comma time either a tertiary or maybe something that's conjugated something like that so that's you'll see it like that so you will you won't see is a secondary cover can to a secondary ,comma kind that's equal stability even all that really does have cover that not very well-behaved question the 2nd 1 is is going to give you a of attentive substituted out himself on the most stable product is going to come from this cover Karen OK yet along with the yes we're not going to see them moving to carbons over just 1 part of it so in the 1st example of sewing and the other question that I get is in this 1st example why did we might real hydrogen had we know we'll migrated Corrigan sold show you what I'm talking about so we moved out of migrated or hired him how are we supposed to know that enacted doesn't migrate bullets answer that I wanted show that that's at the very end of the scale Shh let's try it would try another migrate instead many go here all right so why doesn't that hired why doesn't that happen yeah I'm just going from a secondary to a 2nd OK so in this happy little bubble of the 1st year of organic chemistry when everything that works as opposed to working and all that but this is not going to happen because we're going from a secondary to a 2nd case in real life that could happen not something we're going worry about for this class alright alright so
whenever a reaction leads to the formation of a common plan anatomy includes reactions that includes as 1 reactions he won reactions from Chapter 7 and 8 you must check its structure for the possibility of rearrangement will I tell you it pain this going rearrange know you're going to know that you form a secondary ,comma Academy where reform secondary ,comma Academy to look for rearrangement so you you need to know how to do that on your all I'm not going warning OK so this guy these aren't expected the ones from range cover campaigns I'm going to put an asterisk next to them so this 1 here that 1 here which was made which product is major we think the 4th product Texas substituted alkyl and here's a dehydration example this is just like the 1 that we just didn't and so on definitely this is the rearrange products so that's what the asterisk means from rearrange product and so definitely this one's going to be the major the 2nd 1 drawn attaches substituted alkyl are excellent summaries dehydration reactions use
H 2 hours of work concentrate in order to it but as age of sagacity from concedes We want peace favors elimination Wordsworth was secondary or primary alcohols don't use retiree oddballs Uselton and shown on occasion and that was what 46 47 was therefore is 47 the change at all for himself what's for rearrangements especially with secondary alcohols and most highly instituted there the McCain are excellent dehydration Oregon and Morgan and move on to the
2nd part of this chapter which is
all about taking alcohols and alcohol as a really for leaving the dozen taking alcohol and converting it into something that has a good leaving group that's that's the major of the bulk of this middle part of this chapter and so an alcohol cannot undergo nucleophilic substitution because it has a strong basically because that cannot be displaced by nuclear file so if you're thinking that this can happen and we wanted to take another look at Chapter 7 what we said in Chapter 7 is we're not going to have hydroxide as a leading group in unison to reaction so if you're thinking this is going to happen and that's not going to happen but for the big extra that that's not gonna happen but were reduced to figure out some way is that we can make a similar thing happened not by by this method but by something that's a little bit different and this is all because this is a bad leaving group it's a strong base we know that the leading groups are weak faces strong basis the day of the conjugate acid punch Hasidim hydroxide is water but is approximately 15 so that sort of in our category of badly groups Barak so as to whether we in alcohol can undergo substitution it's always group is
converted into a group that's a better living room so how about a halogen if we can take that hydroxyl who can't do it this previous way that we have on this page but if we take that hydroxyl and we will make up them we converted into a hang-glider we can do all the reactions from Chapter 7 8 right so and is a way to do that we can take the alcohol and to territory with Ajax converts the bad leaving group hydroxyl into a great meeting group and so this is what it looks like Dad leading Group it was review will we have previous page piece PKA of the conjugate acid each 2 is about 15 and we treat us with HP are we can actually converters In method for In an product is water the price so now undertaken that bad Aberdeen Group and converted into a great leaving groups the game animals really needed day of the conjugate acid and HP or yeah is minus 8 it's a fantastically groups so that's what we wanted to take the alcohol and converted into an uncle he like so that's where as the 1st reaction talk about this section it turns out that we could do this with primary secondary
and tertiary alcohols all undergo nucleophilic substitution when treated with HIH MHC altered form alkyl here no staff around this agent does not work in this reaction so long primary secondary and tertiary the can be converted into R X where X equals eyes the and see so that's that her doing his part of the chapter mechanism is going to depend on the alcoholic you so primary alcohols methanol reaction proceeds through as too-tight secondary alcohols and tertiary those a perceived by bias and one-time mechanism so it's it's similar to dehydration we have a different mechanism depending on alcohol we started so primary alcohols enough offers 1st step so this is
a potential mechanism for Mitchell I'm right what are the potential mechanisms for mid-term 1 we have elimination we have the 1 we have the 2 we also have dehydration dehydration with the primary alcohol and dehydration was a secondary or tertiary so we're already getting quite a list of possible mechanisms this is another possible mechanisms out for mid-term 1 can you pretty much guaranteed to have more than 1 mechanism on this 1st match he II emphasize mechanisms quite a bit because they help you organic chemistry they help minimize your memorization OK so it's really helpful Lara rights looks like the 1st step of dehydration doesn't it all right and what we've done there is found in a kind of a roundabout way we've taken are so badly .period and a good living intermediate :colon now in step 2 of this reaction organizers redraw events far good nucleophile growing on is a very good nuclear file that country In us into so bromides here so that's that's a condom bases in a community backside attack kickoff are leaving and it consumer aside product is coming from that's when water leaks seoul we've gone from about leaving room for an hour alternate products here he is ,comma this which has a great waiting questions on mechanism for primary alcohol and HP are anybody let's look at secondary madam procedure doesn't
want tight mechanism here's an example here tertiary alcohol HI converted into them interview iodide alright so that's step 1 is going to be exactly the same when approving the alcohol so let's do that here I rights on pretty particularly mechanisms and was the lone pairs all reacted patterns if you're breaking a bond I want you to drive drive the bonds that operating there was need to come from a long period of horrible and so here this error was coming from a long period the 2nd error was coming from a fall so look like that this is a very fast reaction acid-base reactions are extremely fast such a fast reaction Meretz was voted the alcohol now if you thinking that I'd I'd community and community backsides that that's not gonna happen why is that it's a tertiary alcohol it's a tertiary so that's not going to happen Barak so we're going lose water to form a current account the Salford is looking just like dehydration interpreted alcohol tertiary cover can I'm sending will have secondary will go secondary Cobb and if we get a secondary ,comma Qatar would we watch out for yet if you can have it can always happen but them so this is faster slow steps slow step away from a car mechanic and then we have nucleophilic attack at the curb account summary jobless OK so there's going to come from 1 of the long on iodine iodine is involved in India pushing for the steps meet all of its appears as they common attacks the Kerber Catherine this is also a fast reactions so that's the mechanism that we're going to see what we have a secondary or tertiary alcohols all right for him .period order reactivity agent for
Ajax HI as fast as well always HP awful by HCl then why is the White a seal slaughter well it's really comes right down to the stuff right here chloride ions so we could live with OK so I'm at slower slower because see is a weakening good and it's only contracted in your book your text book the book uses zinc chloride to promote the reaction to promote reaction In other words of HCl on its own isn't good enough so they take HCL and reactive this inquiry I'm not having to worry about the zinc chloride I think we're just going to pretty much stick to HIH the R can avoid the whole zinc chloride issue altogether is so that's why How I usually handles questions on that point anybody by rights ordering activity for alcohols tertiary is faster than secondary is faster than primaries faster than mouthful OK so these guys around these would be the result these undergo arson was sent to these guys undergo SN 1 so what that saying is that as secondary alcohol it's faster to make the Cobra pattern is to undergo backside is much faster for secondary ,comma parents 1st secondary alcoholic Aqaba County may be a little surprising but that's something that's really what that is telling us so it's an Castro where a secondary alcohol to form a part of a Academy then to undergo fax Itar-Tass so passengers maybe surprising that actually cases actually faster and not because of 1 s 2 secondary Ontario and it's beginning to get very hysterical and slows reaction down on tremendously so this reaction is our best for primary menthol and tertiary substrates reaction doesn't work well for secondary and I don't want you to use it for secondary readership you alternatives coming up OK so don't use for secondary substrates if we have a a secondary alcohol we turn it into a an alkyl here libraries in other regions don't use for secondary substrates why is this why why not secondary substitutes are so there's no reason that the long reason secondary substrates like can undergo 1 you want Anderson to meet you depending on the conditions used under the conditions of this reaction strong acid strong acquiesced assets and someone 131 pathways are favored over and to the 2 pathways for secondary substrates faster to make a complicated that it is to undergo backside attacked so the reaction proceeds by way of a car mechanic intermediate which can rearrange so now and now they were learning to rearrangements that's what's going on and after worry about those have so it's going through this example any OK it struck the product to that step we have no proof media alcohol this is a secondary alcohol we have appropriated on alcohol so the next step is going to be for the leading group to leave L so let's try other permeated out and this and this is going to leave arrangements Straw that cover Kennedy we've already seen a a couple times and you'll see the discussion also this week the peso secondary ,comma caring legal officer had saying OK we look for rearrangements of arrangements and we have a nice rearrangement here we can do I want to hydride share so any change colors from like that so the area should come from that carbon hydrogen bond to move over to the carbon so there's a tertiary cover Calderon so on either 1 of those products can be we departs from them from both of those let's drop both of them if the bromide attacks before debt rearrangement happens we can get this product or if we I'm doing 1st before the bromide attacks and I'm skipping a step here then we can get this far so know that is that reaction and you're trying to do actually yields to products sold with we wanted to get the range products then we would have to do separating at 2 separate those 2 problems which is not trivial to do was a pretty similar physical properties it's going to be attracted are so I only wanna use an alternative yes questions the used before arrangements he was yes not really will tightly controlled will talk about that after class OK that's reason number 1 rearrangements right reason numbered Stewart's talk about the staring chemistry of this reaction you lot staring chemistry right middle only eastern chemistry but difference on the substrate used primary alcohols I might give you a problem like this on the testimony expected to show the stirred chemistry in the so let's say we started off with this optically pure primary alcohol How do we have enough with your primary alcohol used interior from 1 of the hydrants to distinguish those 2 hydrogen from each other let's go through the mechanism if you know the mechanism you will have no trouble predicting the father if you don't know the mechanism is a 50 50 guests so we'll see how old you are on the test if you just do a 50 50 guests must go through it we know the mechanism so this should be easy to predict the hydrogen is going back to change forward far-right what happens next elimination right no the substitution rights yet theatrical but decided attack SAN to inversion of configuring a ship fastened to inversion of configuring action so it was short version of configurations going to have the bromide coming in from the opposite side there's more than 1 way to show a version of configuration if you have another way to do it that's also fine and if you have the needless thought coming from the opposite side and we just moved the hydrogen over to the side and we moved the deuterium but would keep them in the same then I will give you on so that's as version of configuration is 100 per cent conversion configuration so 100 per cent inversion need to know that so when the product we will draw inversion what happens in the secondary era tertiary alcohol let's go through that if we know the mechanism that's not a hard question Trevino mechanism and we know the structure of Aqaba Catherine that is not a hard question it's really not a 50 50 guests could you could have 1 injury could have the other could have called right so that's own one-third of one-third of its guess we all wanted a chance to get it right alright so let's go through them In effect here we know a little bit about the structure of Aqaba Cannon so this is a secondary alcohol under these conditions the alcohol least for macabre Catherine and we do 1 structure of Aqaba Cannon will gosh the carving of of the carpet Catherine 18 and although 3 Adams attached all in the same way hydrogen goes back here we have a fall alright so these guys are all in the same plane not every single added there but all of these groups this carbon which is the cargo Catherine this carbon that hydrogen in this car along the same way so now think about the next step in this reaction will Costa Rica still get will talk more about this on Friday
Reaktive Sauerstoffspezies
Bukett <Wein>
Chemische Bindung
Substrat <Chemie>
Elektron <Legierung>
Fülle <Speise>
Chemische Reaktion
Chemische Bindung
Wässrige Lösung
Chemischer Prozess
Nucleophile Substitution
Elektron <Legierung>
Funktionelle Gruppe
Aktivierung <Physiologie>
Setzen <Verfahrenstechnik>
Gangart <Erzlagerstätte>
Chemische Formel
Alkohole <tertiär->
Diamantähnlicher Kohlenstoff
Barrel <alpha, beta->
Funktionelle Gruppe
Substrat <Chemie>
Organische Verbindungen
Chemische Forschung
Chemische Forschung
Freies Elektron
Chemische Struktur
Proteinkinase A
Schweflige Säure
Aktivität <Konzentration>
Einsames Elektronenpaar
Substrat <Boden>
Minimale Hemmkonzentration
Eliminierungsreaktion <alpha->
Chemische Eigenschaft
Chemische Struktur


Formale Metadaten

Titel Lecture 7: Conversion of Alcohols to Alkyl Halides
Serientitel Chemistry 51B: Organic Chemistry (Winter 2015)
Teil 07
Anzahl der Teile 26
Autor King, Susan
Lizenz CC-Namensnennung - Weitergabe unter gleichen Bedingungen 3.0 USA:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen und das Werk bzw. diesen Inhalt auch in veränderter Form nur unter den Bedingungen dieser Lizenz weitergeben.
DOI 10.5446/21626
Herausgeber University of California Irvine (UCI)
Erscheinungsjahr 2015
Sprache Englisch

Inhaltliche Metadaten

Fachgebiet Chemie
Abstract This is the second quarter of the organic chemistry series. Topics covered include: Fundamental concepts relating to carbon compounds with emphasis on structural theory and the nature of chemical bonding, stereochemistry, reaction mechanisms, and spectroscopic, physical, and chemical properties of the principal classes of carbon compounds. Index of Topics: 00:11 - Elimination Reactions of Alcohols: Dehydration 08:02 - Carbocation Rearrangement 24:12 - Conversion of Alcohols to Alkyl Halides with H-X

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