POSITION OF THK DOUBLE LINKAGE IN PIPKRITONE. 139 



NOTE ON THE POSITION OF the DOUBLE LINKAGE 

 in PIPERITONE, Part I. 



By A. Li. Penfold, f.c.s. 



With Plate VI I. 



[Bead before the Royal Society of N. S. Wales, August 3, 1921.'] 



Mr. H. G. Smith, F.c.s. and the present author in a paper 

 entitled "On the manufacture of Thymol, Menthone, and 

 Menthol from Eucalyptus Oils," read before this Society 

 in June 1920, x pointed out that piperitone — the ketone 

 found occurring in certain Eucalyptus oils — on account of 

 the formation of the aforementioned bodies was a menthen- 

 one, with the carbonyl group at position 3. These authors 

 were unable at that time to bring forward evidence that 

 would establish the position of the double bond, but con- 

 tented themselves with the statement that it was either 

 in the fourth or first positions, leaving the decision until 

 such time as the evidence in favour of either one or the 

 other was forthcoming, particularly as they were dealing 

 with only those bodies which threw light on the carbonyl 

 grouping. At the time of reading of this paper, they con- 

 sidered there was a little evidence in favour of the fourth 

 position, although the chemical and physical constants of 

 the ketone agreed very closely with those given by 

 Schimmel & Oo. for A^Menthenone-B. 2 



During the past year the writer has carried out a series 

 of experiments on the decomposition of piperitone by means 

 of both alkaline and neutral potassium permanganate solu- 

 tions with a view to deciding the constitution of this 



1 This Journal, Vol. liv, 40, (1920). 

 2 Semi-annual Report, October, 1910, p. 97. 



