Aminoacetone is not a stable compound. It decomposes relatively rapidly. It is however completely stable in acidic media and can be isolated in the
form of its salts (see literature examples of its preparation, where it is always prepared as a salt isolated from acidic media).
It is not prepared by alkylation of ammonia with haloacetones. There have been historic attempts into preparing it this way and some claimed they
isolated it from the product mixture, but the most conclusive attempts indicate this is not possible (see: Gabriel, Ber. 1893, 2197; the
article is freely accessible at Gallica). As I understood the article, the main product isolated from the related reaction of 3-chloro-2-butanone with ammonia was
2,3,5,6-tetramethylpyrazine (thus the aromatized self condensation product of the initially formed aminoketone).
That is no reference in support of your assumption that aminoacetone should form. Firstly, because aminoacetone is an alpha-aminoketone and thus
unstable in basic media. Secondly, because you used a faulty deduction. Chloroacetone and other alpha-halo carbonyl compounds do not behave like alkyl
halides due to the neighboring group assistance. They are isoelectronic with allyl chlorides and therefore do not react via a simple SN2 mechanism. In
fact, I'm not sure there are any conclusive evidence for the mechanism of the nucleophilic displacement at alpha-haloketones. I have not checked for
the latest literature, but I have a book from 1963 (C. A. Bunton: Nucleophilic substitution at a saturated carbon) that provides a number of
hypotheses to explain the reactivity of alpha-halo carbonyl compounds and none seem fully convincing. |
