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Acetamide as a Solvent
BY O. F. STAFFORD
Assuming a measure of validity for the doctrine that a substance dis-
solves other substances of its own kind, a most interesting case should be
presented by acetamide as a solvent. This substance melts at about
80" to form a fairly mobile liquid. The fact that it contains a methyl group
should give it solvent powers for hydrocarbons; its carbonyl group relates
it to ketones, esters and acids; its tautomeric hydroxyl grcup gives it kin-
ship to water and the alcohols; its amino group brings it into line with am-
monia and its derivatives, while the ease with which it yield: nitrile suggests
a relationship to cyanogen compounds. In the field of inorganic chemistry
the above considerations are supplemented by the fact that acetamide
outranks all but a half dozen substances in the magnitude of its dielectric
To test these assumptions the approximate solubilities of some 400 organic
compounds and about half that number of inorganic compounds have been
ascertained. The procedure, in general, was merely to add the substance
to fused acetamide (at about 100°) and to note wether much or
little would dissolve. Where in any instance the solu1)ility thus appeared
to be slight, the influence of higher temperatures w 1s investigated.
Sparingly soluble inorganic compounds were not only testcbd directly, but
in most cases were precipitated by suitable double substitiition reactions.
I t is interesting to note that these precipitation reactions occur with the
same readiness as in water or ammonia as solvent.
The general results may be summarized by saying that of the 400 organic
substances the only one showing no indications of solubility was cellulose.
Asparagine, barbituric acid, oxamifle and uric acid are sparingly soluble
at low temperatures (i. e., below 100°). I t is significant
that these same substances are but slightly soluble in water and are rated
as insoluble in alcohol and ether. The solubilities of the inorganic com-
pounds are strikingly analogous to those in water. Exceptions are pre-
sented by potassium perchlorate, the halides of mercury ar.d lead, and the
phosphate and oxide of mercury, all of which are more soluhle in acetamide
than in water.
More specifically, it was found that among organic compounds sixtyfive
ammonia-nitrogen derivatives (except uric acid), seventeen carbohydrates
(excepting cellulose but including starch), sixty-eight dyestuffs,
forty-four alcohols, eleven nitro and nitroso compounds and a number of
miscellaneous nitrogen derivatives, all dissolve readily. Of the twenty
hydrocarbons tested, anthracene, phenanthrene and triphenylmethane
are quite soluble The others are soluble a t higher temperatures, but
separate out to form two-phase systems at lower temperatures (80 to 120°).
Forty-five acids tested are all soluble, but those with very long
hydrocarbon chains are less soluble than the others.
Some twenty oxygen compounds were tested, in this class the ethers
appearing to be somewhat less soluble than the others.
Among inorganic compounds bismuth nitrate gives a white insoluble
compound similar to that formed by hydrolysis or ammonolysis. Mer-
CUTOUS nitrate undergoes some transformation in contact with the solvent.
A similar action appears to take place with mercurous halides.
Chromates are slowly reduced in acetamide solutions, although even the
solution of chromium trioxide (which in color exactly resembles solutions
of chromates) is stable for quite a while. The brown silver carbonate
precipitate is presumably in the form of silver oxide, as in the case
of precipitation from water.
The close analogy between acetamide and water as solvent is proved not
only by the close correspondence which is shown by solubilities of in-
organic compounds in these two substances but also by the chemical be-
haviors of dissolved substances. Mention has already been made of the
fact that double substitution reactions occur with the same readiness in
acetamide solution as in water solution. In such cases the precipitates
in acetamide are even similar in appearance to those formed in water,
colored sulfides, for example, appearing precisely as when precipitated
from water. A search of the literature reveals that conductivity curves
for a considerable number of salts in acetamide solution have been deter-
mined and that these curves resemble those obtained in water solutions.
Furthermore, it has been shown that electrodeposition occurs readily in
acetamide solutions with metals not more active than zinc. Numerous in-
stances are described in which acetamide seems to function analogously
to water of crystallization.
It follows, therefore, that the expectations enumerated in the opening
paragraph of this article are surprisingly substantiated by experiment.
Seemingly acetamide has a wider range of solvent powers than any other
substance which has been reported.
RECEIVED MAY 29, 1933
PUBLISHED OCTOBER 6, 1933
J Am Chem Soc, 1933 55(10): 3987-3988
"Acetamide as a Solvent"
O F Stafford
J Am Chem Soc, 1930 52(7): 2693-2698
"ACETAMIDE AND FORMAMIDE AS SOLVENTS FOR THE ELECTRODEPOSITION OF METALS"
L F Yntema, L F Audrieth
preparation of acetamide: Post 330416 (3base: "refs: preparation of acetamide", Chemistry Discourse)
Thanks 3base, that was quite interesting.