266 



SCIENCE PROGRESS 



methyleugenol and methylisoeugenol is shown in the following 

 scheme : 



CH 2 . CH : CHj 



Methyleugenol : not changed after 

 18 months. 



CH:CH.CH a 



O 



o 



\:H 2 



Isosafrole gives some di-isosafrole 

 with much resin. 



OMe 



OMe 



Methylisoeugenol gives 

 di-methylisoeugenol. 



A striking change, allied to polymerisation but accompanied 

 by elimination of hydrogen bromide, is that observed by the 

 writer 1 in the case of 3 : 6-dibromo-/3-naphthaquinone when 

 exposed in certain solvents (ethylic acetate, benzene or chloro- 

 form) to the action of light; this substance, which in the dry 

 state undergoes autoxidation (see p. 263), in presence of the 

 solvents named is transformed as follows : 



O 



Br 



O 



Br 



HBr + 



Br 



ox< 



< 



Br 



Purified benzaldehyde, exposed to light in the dry state 

 during two and a half years, in absence of air, is converted into 

 an amorphous material which is apparently a tetrameric form 

 (C 7 H 6 0) 4 . 2 



Small quantities of two trimeric forms 3 are also produced, 

 one of which was obtained by Mascarelli 4 as the principal 



1 Brit. Assoc. Refiort, Committee on Isomeric Naphthalene Derivatives, 

 1902. 



* Ciamician and Silber, Atti R. Accad. Lincei, 1909, 18, i. 216 ; Ber. 1909, 42, 

 1386. 



1 Atti R. Accad. Lincei, 191 1, 20, i. 881. * Gazzetta, 1912, 42, i. 82. 



