Pumukli
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Amidation
Hello,
There is a probably well known reaction between esters and ammonia (or primary or secondary amines) which results an amide. So far so good. :-)
I was wondering what could happen if aqueous solutions of ammonia or the amines were used instead of the pure, anhydrous compounds?
I understand that the amines are more nucleophilic than water but would this difference in their nucleophilicity provide a good safety margin to
achieve the same results in aqueous solutions or the ester hydrolysis would be too pronounced?
I mean I could probably live with 1% hydrolysis product but purifying 10% or more such compound would be more painful (and consume 10% or more
starting material).
Any thoughts on the matter?
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aga
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Quote: Originally posted by Pumukli  | | There is a probably well known reaction between esters and ammonia (or primary or secondary amines) which results an amide. So far so good. :-)
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Might be well known to you, but not to me.
Any chance of a reference to that so i can join the Well-Known-To-Club ?
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AvBaeyer
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Here you go:
From Norris, Experimental Organic Chemistry, 2nd Edition, 1924 (a free book):
Preparation of Acetamide from Ethyl Acetate (SECTION
221).—Mix in a 250-cc. distilling flask 50 grams of ethyl acetate
and 100 cc. of a concentrated aqueous solution of ammonia
(sp. gr. 0.90). Close the flask with corks and let the mixture
stand over night, until the two layers first formed have disappeared.
Arrange the flask for distillation with a
thermometer and water condenser, and use as a receiver a
distilling flask or a filter-bottle, the side-arm of which is provided
with a tube which dips under water; the latter precaution is taken
to absorb the large quantity of ammonia which is given off in
the distillation. Distil carefully; collect the first part (about
10 cc.) of the distillate separately and test it for ethyl alcohol
When the thermometer registers 160°, replace the water-condenser
by an air-condenser, change the receiver, using this time
a beaker, and collect what distils at 160°-225°. As the temperature
rises the acetamide solidifies in the condenser to a crystalline
mass. which can be readily liquefied by warming the condenser
cautiously with a free flame. When the distillate is cold pour
off from the crystals in the receiver any liquid present, and dry
the crystals on a porous plate. Weigh the product obtained
and determine its melting-point. Calculate the percentage
yield obtained. The slightly impure acetamide may be purified
by a second distillation, or by crystallizing it from a mixture
of one volume of alcohol and two volumes of ether. If the
product obtained in the first distillation does not melt sharply,
recrystallize a small portion of it.
Acetamide melts at 82°, and boils at 222°. The yield obtained
in the preparation should be about 65 per cent of the theoretical.
This should work for many esters that have some water solubility.
AvB
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