thesmug
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Methylation
I've looked everywhere and I can't seem to find anything on this subject. How would one go about methylating something ? I am mostly after methylating
acetone to try to get methyl ethyl ketone (and yes, I know you can buy it).
[EDIT]: Oops, nobody calls acetone "ketone!"
[Edited on 3/4/14 by thesmug]
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Hockeydemon
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You would use a methylating agent. I'm sure someone will correct me if I'm wrong but I don't know that you can easily add a methyl group to a primary
carbon like that. The secondary carbon is much more stable and the sigma bond formed eliminates the more reactive pi bond between C=O.
I could also be completely wrong and not know wtf I'm talking about so we will wait and see I guess.
Maybe using the dangerous diazomethane would work?
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Mesa
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http://www.biologie.uni-hamburg.de/b-online/library/newton/C...
The first 2 or 3 examples may interest you. 
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Metacelsus
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Starting from acetone and using a methylating agent will get you t-butanol (methylation will occur at the carbonyl). You need to start from ethanal
(acetaldehyde) or propanal. This will form 2-butanol, which you will then need to oxidize to the ketone.
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thesmug
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Quote: Originally posted by Cheddite Cheese  | | Starting from acetone and using a methylating agent will get you t-butanol (methylation will occur at the carbonyl). You need to start from ethanal
(acetaldehyde) or propanal. This will form 2-butanol, which you will then need to oxidize to the ketone. |
Oh well then nevermind.
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Theoretic
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Cheddite, that's if it's a nucleophilic methylating reagent. Electrophilic ones are different.
Mesa: true, LDA and other strong bases that convert all acetone to enolate will work. but on a homechemist's setup, perhaps other bases can be
contrived
CaO is definitely strong enough, since it is even able to deprotonate ammonia. This is one route - compress ammonia over CaO+Na2CO3 to liquefy it,
the calcium amide that is generate will react with Na2CO3 to produce NaNH2. This base will work best in ammonia (it is not very soluble in other
solvents, and this may cause the enolate to form slowly, causing side reactions). Cool as well as you can (best if you have dry ice, or CaCl2+ice) and
add acetone in small portions... however mind that both NaNH2 and especially the enolate are water and air sensitive, so you must exclude these
somehow, from the acetone, ammonia and the whole apparatus (NaNH2 and the enolate can form explosive compounds with oxygen). Afterwards, methylating
agent - like methyl iodide - is added in small portions (again dry and air free - best to remove even the oxygen that is dissolved in it). Methyl
iodide is carcinogeic, so care is needed (many other methylating agents are, too)
diazomethane will work on reasonably acidic substrates (up to and including phenols, but not saturated alcohols). However, acetone isn't acidic
enough. In the presence of an acid with a non-nucleophilic conjugate base (HCl is out for instance, because it will form CH3Cl), diazomethane will
become activated, and turn into the methyl ester of that acid. This might methylate the enol form of acetone, and the acid will quickly catalyze the
conversion of acetone into the enol form as it is consumed. You might as well use the methyl ester to begin with (less dangerous than diazomethane),
for instance methyl sulfate (however it is quite toxic and carcinogenic - and can easily penetrate skin). It is made from methanol and excess sulfuric
acid - and to obtain it free from water you should have anhydrous sodium or magnesium sulfate.
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thesmug
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Sorry to bump an old post but could you methylate toluene to selectively make para-xylene?
[Edited on 3/7/14 by thesmug]
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