THYMOL, MENTHONE AND MENTHOL FROM EUCALYPTUS OILS. 43 



Piperitone combines with sodium bi-suiphite without 

 mueli difficulty, but the compound is very soluble in the 

 aqueous solution, if, however, the combination be continued 

 for some days, the saturated solution eventually forms a 

 crystalline mass, from which the pure piperitone can be 

 recovered. 



A sample of pure piperitone, first obtained in the crude 

 condition by distilling under greatly reduced pressure, and 

 afterwards separated from the bi-sulphite compound, had 

 specific gravity at 20° O. = 0*9348 ; optical rotation 

 a D — 40'05°; and refractive index at 20° = 1*4837. It boiled 

 at 229-230° 0. (uncor.) at 760 millimetres, and at 106- 

 107° at 10 millimetres pressure. The semicarbazone 

 melted at 219-220° O. 



Piperitone, which is an unsaturated ketone, forms both 

 an oxime and an oxamino-oxime, which substances melted 

 .at 110-111° C. and at 169-170° C. respectively. 



The molecular refraction for a C10H16O ketone with one 

 double linkage is 45*82; found 46*49. It has, however, 

 been shown by Auwers and Hessenland [Ber. 41 (1908) 

 1812], that menthenonesof this character, with a conjugated 

 double bond, require an addition of 0*83 to the aggregate, 

 and if this addition be made for piperitone the result is 

 closely theoretical. 



On oxidising piperitone with potassium permanganate, 

 isobutyric acid is readily formed as one of the products ; in 

 fact it is difficult to prevent the formation of this substance 

 even when the theoretical amount of permanganate is 

 added in order to oxidise the carbonyl group, the temper- 

 ature being kept down by the addition of ice. 



The formation of thymol shows the carbonyl group in 

 the piperitone molecule to be in the 3 position, and the 

 results so far obtained suggest the double linkage to be in 



