Volume 1

Recent advances in organic chemistry / by Alfred W. Stewart.

  • Alfred Walter Stewart
Date:
1927
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Recent advances in organic chemistry / by Alfred W. Stewart. Source: Wellcome Collection.

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    molecule might be expected to be practically instantaneous ; and 1 us, even if diazomethane exists in two isomeric forms, the isolation of one variety in a pure state may be experimentally impossible. The case of the diazene compounds, in fact, is much more akin to the benzene oscillation phases of Kekule than to tie pseudo-acid type; and there is really no more reason for e eving that diazomethane can be isolated in two forms than there is for supposing it possible to separate two of the benzene oscillation phases from each other. Thus when discussing the problem of cyclic versus open-chain structures for the diazene derivatives, it must be borne in mind that these substances may quite well be supposed to pass from one mode of linking to the other with the least possible change m internal energy; and all that can really be settled in the matter is best method of formulating a reaction which is observed in practice. When hydrazine acts on simple ketones or aldehydes, the products are hydrazones having the structure R2C : N . NH9 ; and these bodies, in presence of excess of ketone or aldehyde’ yield ketazines, R2C : N . N : CR2 . On trying analogous re¬ actions with benzil or the a-ketonic esters, Curtius 1 found that m these cases the products showed no avidity for condensation with extra molecules of aldehyde or ketone. On oxidation, also, the two classes showed differences in behaviour. The derivatives of the simple ketones yielded unstable tetrazone derivatives of the type R2C : N . N : N . N : CR2 ; whereas the products from the dicarbonyl compounds were oxidized to aliphatic diazo¬ derivatives. In order to express this difference between the two series, the hydrazine derivatives of the simple ketones were written in the form (I.), whilst the corresponding substances derived from dicarbonyl compounds were given the cyclic formula (II.) and /NH N (I.) R2C : N . NH2 (II.) R-C( | (HI.) R-c/ll | XNH \]sr n—CO R—CO in this way the cyclic representation made its appearance, since obviously the oxidation product of (II.) must have the structure 1 Curtius and others, J. pr. Chem., 1889, (2), 44, 161, 544 • 1911, (2), 83, 217. VOL. I. F
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