THE CHEMICAL ACTION OF LIGHT 



/-Methylcyc/ohexanone gives 7-methylhexoic acid : 



275 



CHMe 

 H,C f x"\CH, 



H,C 



CH 2 



+ H 2 -> CH 3 .CH,.CHMe.CH 2 .CH 2 .CO,H 



CO 



with some heptenylic aldehyde, CH 2 :CH. CHMe. CH 2 .CH 2 .CHO. 

 Menthone ! behaves as follows : 



CHMe 2 



CH 



+ H 2 -> CHMe 2 .CH,.CH 2 .CH,. CHMe . CH 2 . CO s H 



Wallach's decoic acid. 



CHMe 2 . CH : CH . CH 2 . CHMe . CH 2 . CHO 



New aldehyde isomeric with menthocitronellal. 



When menthone is exposed to the action of water and 

 oxygen 2 conjointly, it undergoes oxidation as if it were sub- 

 mitted to the action of hydrogen peroxide : 



CHMe, 



CH 



H S C 



H 2 C 



CO OH 



+ 

 CH, 



OH 



CHMe 



CHMe 2 



I 

 CH.OH 



/ 

 CH 2 



CH, CH 3 .CO.OH 

 CHMe 



CHMe, 



I 

 CO 



/ 

 CH 2 



CH 2 CH 2 .CO.OH 

 CHMe 



The product is the keto-acid obtained by Arth by oxidising 

 menthol with chromic acid. The ring is split at the same 

 point as when air is excluded. 



The behaviour of dihydrocarvone when exposed in aqueous 

 alcoholic solution to the action of light is interesting in com- 

 parison with that of carvone, which, as stated in Section V., 

 gives rise to an isomeric form resembling camphor ; dihydro- 



1 Atti R. Accad. Lincei, 1907, 16, i. 835 ; 1909, 18, i. 317 ; Ber. 1907, 40, 2415 ; 

 1909, 42, 1 5 10. 



2 Atti R. Accad. Lincei, 1909, 18, i. 317 ; Ber. 1909, 42, 1510. 



