44 H. G, SMITH AND A. R. TENFOLD. 



the 4 position, and that piperitone is A-l-menthenone-3; 

 the only alternative to this being A-l-rnenthenone-3. 



Wallach and Meister, [Ann. 362 (1908) 261] have, how- 

 ever, sIiowq that mentheQOQe with the double linkage in 

 the 4 position boils at 212-213° O.; but Auwers [Ber. 41, 

 (1908) 1801, and 42 (1909) 2408], has expressed doubts as 

 to the correctness of this statement, although Wallach 

 later confirmed bis original determination. (Ohem. Zentr. 

 1912, 11, 922-923). 



The question as to the correct position of the double 

 bond in the piperitone molecule does not affect the con- 

 clusions submitted in the present paper, as menthone would 

 be the reduction product for both the 1 and 4 positions, 

 with the CO group at 3. 



We hope eventually to be able to clear up this point, and 

 to show beyond doubt the exact position of the double bond 

 in piperitone. 



Preparation of Thymol. 

 60 grams of pure piperitone were added to a solution of 

 175 grams ferric chloride, 160 c.c. glacial acetic acid, and 

 500 c.c. of water. The whole was then heated on the sand 

 bath to boiling. The reaction takes place according to the 

 equation 2 Fe0l 3 +H 2 O = 2 FeCl 2 + 2 HC1 .+ O, and was 

 completed at the expiration of about one hour. Tiie reaction 

 product was then steam distilled, the phenol separated and 

 absorbed in a 5 per cent, solution of sodium hydrate, the 

 unabsorbed oil removed by ether, and the aqueous layer 

 decomposed by hydrochloric acid. The phenol was finally 

 distilled under reduced pressure when the thymol came 

 over at 110-111° C. at 10 millimetres. In this way we 

 obtained a 25 per cent, yield of the weight of piperitone 

 taken; but, no doubt, methods can be devised whereby 

 almost a theoretical yield could be obtained. The change 

 in molecular arrangement from piperitone to thymol is: — 



