THE JOURNAL OF PHARMACOLOGY. 



I OH (4) 

 Protocatechuie Acid (a) 1 OH (3) 



( COOH (1) Carboxy 1-dioxy 3 4-Benzen 



t OH (4) 

 Ce H 3 \ OCH 3 (3) Mono-methyl Protocatechuie Acid 



( COOH (1) Carboxy 1-methoxy 3-oxy 4-benzen 



Vanillic Acid 



t OH (4) 

 C 6 H 3 ■< OCH3 (3) Methyl Protocatechuie Aldehyde' 



( COH (1) MethylaJ 1-methoxy 3-oxy 4-benzen 



Vanillin 



37 



COH 



Dimethyl Protocatechuie Aldehyde Methylene Ether of Photocatechuic Alde- 

 hyde (Heliotropin Piperonal) 



PREPARATION. 



I. (a) Oxidation of aliphatic side chains in coniferin (glucovanillin, oli- 

 vin-acethomovanillic acid, acetoferulic acid), yielding an aldehyde group, 

 while the hydroxyl and methoxy groups are already in their proper position 



(b) From eugenol, iso-eugenol (eugenol-acetic acid, acetiso-eugenol, 

 benzyl-iso-eugenol, methylene, iso-eugenol, iso-eugenol-phenyl-acetic acid 

 and iso-eugenol-toluic acid) by oxidation. 



Peroxide of hydrogen and sodium peroxide have been employed as oxi- 

 dizing chains in late patents. In another patent electric oxidation has been 

 referred to. Usually derivatives of and not eugenol itself are employed. 

 This is done to protect the phenol group in these compounds from oxida- 

 tion. Such compounds in which the hydrogen of the free hydroxyl group 

 is replaced by a substituting group which is readily removed by oxidation, 

 if preferred. For example, acetyl-eugenol. 



I 0-CH 3 CO (4) ( 0-CH 3 CO (4) ( CH (4) 



C, H, ■< 0-CH 3 (3) C„ H 3 ) 0-CH 3 (Saponified)-C e H 3 - OCH 3 (3) 

 ( CH 3 CH CH 2 (1) ( COH ( COH (1) 



Acetyl-eugenol Acetyl Vanillin Vanillin 



In place of the acetyl derivatives others have been employed, as, for ex- 

 ample, by the action of methylene chloride on eugenol-sodium, methyleiie- 

 bi-eugenol results, which on oxidation yields methylene-bi-vanillin. This, 

 when converted into a hexa-chloride derivative and treated with hydro- 



