— 179 — 



to 177° is precipitated. The filtrate of the zinc salt, upon the addition 

 of hydrochloric acid, yielded an acid phthalate, m. p. 93°, which may also 

 be readily separated in the form of a calcium salt. The corresponding 

 alcohol is l-methyl-3-ci/cZohexanol: b. p. 173° (752 mm.), d^ 0,912, m. p. of 

 the phenylurethane 96°. The phthalate with m. p. 129 to 131° is that of 

 the i-menthol with m. p. 34° (b. p. 103 to 105° at 16 mm.), which yields 

 a phenylurethane, m. p. 104° and an acid succinate, m. p. 85 to 86°. To the 

 alcohol corresponding to the acid phthalate with m. p. 175 to 177° the 

 authors have given the name of weomenthol. This body melts at 51° 

 and yields a phenylurethane with m. p. 114° and an acid succinate with 

 m. p. 67 to 68°. i-Neomentho\ is identical with the menthol (isomenthol) 

 which has been obtained by Beckmann 1 ) by hydrolysing Z-menthylphenyl- 

 urethane with sodium ethylate at 150°. The acid menthyl phthalate 

 m. p. 177° and the phthalic ester which has been prepared by Enklaar 2 ) 

 from the alcohol which had been formed by the reduction of geraniol, are 

 also probably identical with i-neomGntho\. The menthol with m. p. 34° 

 appears to be identical with Brunei's /?-thymomenthol (loc. cit.) and with the 

 menthol obtained by Kremers 3 ) in the reduction of a synthetical menthone. 



The experiments with natural Z-menthol made by Pickard and Littlebury 

 have demonstrated the uniformity of this alcohol. From the brucine salt of 

 the Z-menthyl hydrogen phthalate they recovered Z-menthol having a specific 

 rotation of — 49,44°. The t-menthol with m. p. 34° was split up, from the 

 primarily produced brucine salt and the cinchonine salt of the acid phthalate 

 into Z- menthol ([«] D —48,27°; m. p. 42°) and d- menthol ([«] D +48,15°; 

 m. p. 40°). When splitting up ^-weomenthol into its optical components 

 the authors obtained d-neomtnthol (b. p. 96° at 16 mm.; [>] D + 19,69°) 

 and Z-neomenthol (b. p. 105° at 21 mm.; d^ 0,8995; |>] D180 — 19,62 Q ; 

 "d2oo 1,46031). Neither d- nor Z-weomenthol was obtained in the solid state. 



When oxidised with Beckmann's chromic acid mixture, ^-menthol 

 yielded i-menthone, b. p. 205° (748 mm.) which gave rise to an oxime, 

 (m. p. 80°) and a semicarbazone (m. p. 158°). The oxidation of i-neo- 

 menthol resulted in the same i-menthone. From Z-menthol the authors 

 obtained an Z-menthone of somewhat higher rotatory power ([a] D i 9 o — 29,10°) 

 than is stated in the literature on the subject ([«] D — 24,78 to 28,18°). The 

 oxidation of almost pure cZ-neomenthol led to the formation of an Z-men- 

 thone (b. p. 204° at 750 mm.; [«] D i 9 o 23,3°); Z-weomenthol gave rise to 

 d-menthone (b. p. 204° at 750 mm.; [>] D18 o + 24,85°). Both ^-menthol and 

 jrieomenthol, therefore, yield d-menthone, while Z-menthol and d-neo- 

 menthol both yield Z-menthone. An analogous result takes place in the 

 case of Z-borneol and d-tsoborneol, which, when oxidised, give rise to 

 Z-camphor. 



*) Journ. f. prakt. Chem. II. 55 (1897), 30. 



2 ) Berl. Berichte 41 (1908), 2086. 



2 ) Americ. chem. Journ. 18 (1896), 762. 



12* 



