THE CHEMICAL ACTION OF LIGHT 277 



aldehyde being formed by the scission of the ring in a manner 

 analogous to that which occurs in the cases already considered. 



Fenchone l is changed under the influence of light more slowly 

 but in a more far-reaching manner, carbon monoxide being 

 evolved and a resinous material formed the nature of which 

 is still uncertain. 



The observations recorded on the changes of the cyclic 

 ketones considered above are of special interest from the point 

 of view of the production and transformation of odoriferous 

 principles in plants and the part they play in plant physiology. 

 Among other ketones studied by Ciamician and Silber the 

 following cases may be cited. Pinacolin gives butylene and 

 acetaldehyde : 



CH 3 CH 



:< 



CH3.C.CO.CH3 -> CH 2 :C.CH 3 + CH3.CHO 



I I 



CH 3 CH 3 



Pinacolin. Butylene Acetaldehyde. 



Methylisobutylketone and the ketone methylheptenone 

 (CMe 2 : CH . CH 2 . CH 2 . CO . CH 3 ) do not undergo change 

 under the influence of light. 



Mention may be made in this section of Neuberg's statement 

 that light is capable of causing the hydrolysis of disaccharides, 

 polysaccharides and glucosides dissolved in water containing 

 o"5 to 1 per cent, of uranyl salt. 2 



VII. Changes of Complex Character 



When acetone (one part) mixed with methylic alcohol (two 

 parts) is exposed to sunlight during a year the principal pro- 

 duct is one formed by simple addition, viz. isobutylene glycol : 



£}^>CO + CH 3 .OH -> OH.CMe 2 .CH 2 .OH 



But isopropylic alcohol (reduction) and ethyleneglycol are also 

 formed, as follows: 3 



i. (CH a )., CO + CH, OH = (CH 3 \> CH . OH + H . CHO 

 ii. CHs.OH + HCHO = OH.CH 2 .CH 2 .OH 



Glycol. 



1 Atti R. Accad. Lincei, 1910, 19, i. 532. 



2 Biochem. Zeitschr. 1908, 13, 305. 



3 Atti R. Accad. Lincei, 1910, 19, i. 364 ; 191 1, 20, i. 714 ; Ber. 1910, 43, 945 

 and 191 1, 44, 12S0. 



