Abstract
The Ehrlich‐Sachs reaction' consists in condensing a compound containing a reactive aethylenc group, c.g., 2 : 4‐dinitrotoluene, with an aromatic nitroso‐compound, Substituted aldehydcs and ketones may. then b' prepared from the resulting azomethines by hydrolysis With plinerol. acid. Since the yields of final product were ofren mausfactory 11 appeared possible to achieve thc same end by condensing the rcacuve methylene compound with an aromatic aldehyde, e.g. and oxidizing, or ozonizing, the resulting stilbcnc to the required aldehyde.
The polynitrostilbenes, however, proved to be highly resistant to oxidation and the strenuous conditions required to achieve success resulted in the formation of the corresponding acid. Ozonolysis, likewise, furnished chiefly the acid, although small quantities of aldehyde were isolable (compare Kaslow and Stayner'). Since the hydrogen peroxide formed during the decomposition of the ozonide might be responsible for the oxidation of the aldehyde to thc acid, reducing gcnts such as aqueous fcrrous sulphatc were used to dccomposc the ozonidc, but :he main product was still the acid. From this result it seems probable that there is a peroxide present which inevitably produces the acid on hydrolysis.
The work instigated an investigation into the reactivity of methylene groups in general, the results of which will be published later. A number of improvements in stilbene production are recorded. Thus the yield of 2 : 4‐dinitrostilbene was maintained by using toluene as a solvent and the product was much more 'readily purified than that obtained without a solvent. The crude yields of stilbcnes frequently quoted in the literature arc of little value, since tlic final yield of pure matcrial is often considerably lower. For instance, in the preparation of 2 : 4‐dinitrostilbcnc, Thiele and Escalcs' crude yield of 90‐95 is attainable, but the final yield of pure product amounts to about 759 the rcmaindcr being an intracrablc tar.
Benzoyl p‐hydroxybenwldchyde and z: 4‐dinitro‐bcnzoyloxy‐stilbenc do not appear 10 have bcen described previously.