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chemrox
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[*] posted on 20-2-2008 at 10:07
methyl formate


The powers that be, in their infinite wisdom, have limited access to N-methylformamide. I want some and propose to get it by way of methyl formate. The latter material I propose tomake thus:

Formic acid is combined with sulfuric in a distillation flask equipped with condenser and receiver. MeOH is added slowly. Heat is added if needed. As the amide is formed it distills and is collected in the receiver.




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[*] posted on 20-2-2008 at 10:19


Formic + sulfuric acids is used in the lab to produce carbon monoxide. Formic acid is a strong enough acid that in most cases it serves as its own catalyst.

I think you meant the you distill the ester out, not the amide. You'll want at least a short fractionating column, and good cold water in the condenser; likely want to cool the receiver as well. Good prep to do in the winter in an unheated room, or a shed.

Note its low flash point and moderately wide explosive limits.
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[*] posted on 20-2-2008 at 10:29


Yes, methylformate is easily made with only MeOH and formic aicd, maybe a little dry HCl gassed in there can help.
But for aminolyse of the ester, you could just aswell make ethyl formate, which is less volatil, then distill/dry your ester, and gas it with methylamine gas, leaving the solution to stir a few days before distn. Is that the idea you had?
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[*] posted on 20-2-2008 at 12:47


Don't add any acids to formic acid, not even a little HCl, it is very prone to dehydrate into CO. As said, formic acid is strong enough to catalyze its own esterification.

Since both methyl and ethyl forrmate have lower boiling points than formic acid and the alcohol, the equilibrium can simply be shifted to the product side by slowly distilling off the ester.

As I have experienced myself, the ammonolysis of ethyl formate is rapid and strongly exothermic with aqueous 20% ammonia solution. In contrast to the preparation of acetamide from ethyl acetate and ammonia, which takes several days, the analogous preparation of formamide is over in a few minutes after mixing the ingredients.
Since methyl formate has a low boiling point, this could potentially cause a runaway with uncontrollable boiling if you don't cool the reaction or add the ester too rapidly.

N-Methylformamide would be made from ethyl or methyl formate and aqueous methylamine.




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[*] posted on 20-2-2008 at 13:02


Thanks for clarifying the issu with formic acid and HCL. I didn't know HCl had the same effect. It made me realize I did a few mistakes in the past, adding 10% HCl to residu containing ~50-100mL HCOOH and refluxing. That must have generated noticeable amounts of CO, thankfully I'm still alive because of good ventilation.
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[*] posted on 21-2-2008 at 00:27


so.. combine MeOH & formic and dsitill with much cooling?

how about bubbling Me-am through formic? (post edited to ask this latter)

[Edited on 21-2-2008 by chemrox]




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[*] posted on 21-2-2008 at 02:12


Quote:

how about bubbling Me-am through formic?


You get the salt - ammonium formate analogue - which can be dehydrated by further heating. Works with ammonia too, although heating ammonium formate with urea works better for that.

FYI - a early 1900s prep of formamide using ethyl format and ammonia, should be able to use the lower amines as well http://preview.tinyurl.com/2qmzda
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[*] posted on 21-2-2008 at 03:18


The analogous preparation of ethyl formate is in Vogel.

I suspect that the intended use of the amide is Leuckart-related. Making and purifying precursors is probably wasteful, when the reaction proceeds probably little worse with in situ material in typical excess, i.e.:

[The amide:]
General Method.
In a distilling flask fitted with a cork bearing a thermometer extending nearly to the bottom is placed 4 moles of alkylammonium formate prepared by adding the proper amine to cold formic acid. The temperature is raised slowly to 180-190° and this temperature maintained as long as water distils.

[Use for obtaining secondary amines from acetophenones, in 50-80% yields:]
After cooling, 1 mole of ketone is added and the mixture heated until boiling begins; water, carbon dioxide, and amine distil and are collected in concentrated hydrochloric acid. In case any ketone distils over, it is returned to the flask at intervals. The temperature of the boiling mixture is 190-230°, which is maintained for four to eight hours, after which the mixture is cooled and diluted with 3-4 volumes of water, giving oily and aqueous layers. The aqueous layer, mixed with the hydrochloric acid used in collecting the distilled amine, is concentrated to give the hydrochloride of the excess of amine used. The oil is refluxed for several hours with 150-200 ml. of hydrochloric acid per mole of ketone taken, and after the hydrolysis is complete water is added, the solution filtered through moist paper to separate resinified material and the filtrate, if not clear, extracted once or twice with ether. In some experiments the amine hydrochloride crystallizes on cooling. The aqueous solution is made alkaline with ammonia, extracted with ether, the ether solution dried with sodium sulfate and saturated with hydrogen chloride to give the amine hydrochloride. The product is purified further by dissolving in absolute alcohol and precipitating with absolute ether.

JACS 61, 520 (1939)
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[*] posted on 21-2-2008 at 19:50


Methyl formate can be synthesized by heating methanol with sodium formate and hydrochloric acid with subsequent distillation :D Rectification is used for further purification :P



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chemrox
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[*] posted on 21-2-2008 at 22:48


Quote:
I suspect that the intended use of the amide is Leuckart-related.


No-completely different direction. Why speculate? BTW I'm not a Leuckart fan with so many better ways to accomplish the same ends.

I do thank you for the information.




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[*] posted on 1-3-2008 at 06:50
bubble amine through acid


You can bubble amine through acid according to the attached.

Attachment: aliphatic amides.pdf (312kB)
This file has been downloaded 798 times





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[*] posted on 1-3-2008 at 08:45


Note that process, which has been used industrially, uses a large excess of the amine. You're working with an equilibrium

( RCO2H + NH3 ) <=> RCO2NH4 <=> ( RCONH2 + H2O )

an excess of amine both pushes the left reaction to the salt, and sweeps away the water formed to drive that over to the right. You can get away with only a small excess of amine if you're good at separating the water from the salt and free acid. And for simple amides using a large excess of ammonia usually isn't a problem.
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