— 161 — 



occurring in the isomerides, m. p. 139 to 140°, feeble dextrorotation; 

 m. p. 160,5 to 161, 5 , M D in benzene solution-)- 15 8° 30'; m. p. 

 136 to 1 3 7 , inactive. The analogous methyl, n-propyl, isobutyl, and 

 isoamyl benzylmenthones were syrupy, and, according to the analyses, 

 not yet pure. 



Sulphureted reaction-products of menthone with phosphorus trisul- 

 phide have been obtained by N. Speranski 1 ). When 1 mol. phos- 

 phorus trisulphide is heated with 3 mol. menthone to 1 40 , there is formed, 

 besides menthene of the b.p. 168 to 170 , thiomenthone C 10 H 18 S, 

 a reddish liquid of peculiar odour, and readily soluble in the usual 

 solvents; b.p. 217 to 220 ; diso 0,9398. This body is decomposed 

 by prolonged standing, with separation of hydrogen sulphide. With 

 alcoholic solution of mercuric chloride, thiomenthone gives a crystalline 

 precipitate. In addition to thiomenthone, there is formed in the 

 above reaction menthene sulphide C 20 H 34 S of the m.p. 50,5° and the 

 b.p. 2 1 3 (28 mm. pressure). The compound absorbs 4 atoms bromine. 

 It has not yet been possible to determine the constitution of menthene 

 sulphide. Compounds such as methylhexanone, camphor, etc., also react, 

 according to Speransky, with phosphorus trisulphide. 



With regard to the splitting up of menthone by the chemical 

 action of light, see under Physical Notes, p. 124. 



Nopinone. A considerable time ago v. Baeyer and Villiger 

 discovered among the oxidation - products of turpentine oil, nopinic 

 acid C 10 H 16 O 3 , which on further oxidation yielded the ketone 

 nopinone C 9 H 14 0. These two bodies, which are derived from the 

 hydrocarbon nopinene (/}-pinene) contained in turpentine oil in the 

 following manner: — 



H,C:C(H 3 C\ -4 HOOC-(OH)C(H 3 c\ -> OC(JH 3 c\ 



\ CH 3 / \ X CH 3 / \ X CH 3 / 



have been examined more in detail by Wallach 2 ). 



The acid was produced by the following method: 300 g. freshly 

 distilled pinene are shaken with a solution of 700 g. potassium per- 

 manganate in 9 litres water, to which 150 g. caustic soda are added. 

 When the oxidation is completed, the unchanged hydrocarbon is distilled 

 off with steam, then the manganese dioxide filtered off, and the nitrate 

 evaporated to 3 litres. On cooling, sodium nopinate crystallises out. 

 The yield is at most 2,5 to 5°/ of the pinene. Nopinic acid is lsevorot- 



1 ) Journ. Russ. phys.-chem. Soc. 38 (1906), 1346. Accord, to Chem. Zentralbl. 

 1907, I. 1746. 



2 ) Nachr. K. Ges. Wiss. Gottingen 1907, Meeting of 8. June. 



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