THE CHEMICAL ACTION OF LIGHT 261 



and 0-nitrobenzylideneaniline is transformed into the anilide of 

 0-nitrosobenzoic acid (44 per cent, yield after eight days). 



r „ /NO, r „ /NO 



^««4\cH:NPh ■*" Uart «\CO . NHPh 



In the same way 4-chloro- or 4-bromo-2-nitrosobenzoic acid 

 can be prepared by exposure to light of solutions of 4-chloro- 

 or 4-bromo-2-nitrobenzaldehyde in benzene, 1 whilst the ethylic 

 salts are obtained on exposing the alcoholic solutions. ^-Chloro- 

 onitrobenzylideneaniline in toluene similarly gives 4-chloro- 

 2-nitrosobenzanilide. 2 



The nitroso-acids themselves undergo further change when 

 exposed to light, giving a complex mixture of products similar 

 to that obtained by Bamberger by the action of aqueous alkalies 

 on nitrosobenzene. 3 



A very striking instance of intermolecular oxidation-reduction 

 is the transformation of solid benzylidene-o-nitroacetophenone 

 into indigotin under the influence of sunlight : the action is as 

 follows : 4 



OCO . CH : CH . C 6 Hj O a Nj^N 



N0 2 C S H 5 . CH : CH . COk^J 



■0 



CO x /NH, 



>C:C< I +2C 6 H s .CO.OH 



NH/ \CO 



Indigotin. 



The nitro-group supplies oxygen for the formation of the benzoic 

 acid. 



With these changes may be classed the interesting trans- 

 formation, under the action of light and traces of iodine, of 

 benzaldehyde into benzylic benzoate, recently observed by 

 Mascarelli and Bosinelli. 5 This result, which is fundamentally 



1 Sachs and Kempf, Ber. 1902, 35, 2704. 



3 Sachs and Kempf, Ber. 1903, 36, 3299. Sachs and Sichel, Ber. 1904, 37, 

 1861. 



3 Compare Ciamician and Silber, Atti R. Accad. Lincei, 1902, 11, i. 277. Thus 

 ethylic nitrosobenzoate gives in alcoholic solution mainly ethylic-<?-nitrobenzoate, 

 diethylic azoxybenzenedicarboxylate, CO.Et . C 6 H 4 .N.N. C 6 H 4 . C0 2 Et, with some 



O 



free azoxybenzenecarboxylic acid and ethylic anthranilate, NHj . C 6 H 4 . C0 2 Et. 



4 Engler and Dorant, Ber. 1895, 28, 2497. 

 & Gazzetta, 191 2, 42, 82. 



