The constituents of the essential oil of American pennyroyal / by Marmaduke Barrowcliff.

  • Barrowcliff, Marmaduke.
Date:
1907
Catalogue details

Licence: In copyright

Credit: The constituents of the essential oil of American pennyroyal / by Marmaduke Barrowcliff. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    0-1187 gave 0-3392 CO2 and 0-1247 HoO. C = 77-9; H = ll-7. CjoHjgO requires C = 77-9 ; H = H‘7 per cent. = 0-8961 at 20°120°; +43°36' in a 1-dcm. tube, -whence [a]o -f48-6°. It seemed likely that this ketone was a stereoisomeride of Z-menthone, as the physical constants of the two compounds, with the exception of the optical rotation, were practically the same. Its oxime is an. oil. Beckmann (Annalen, 1889, 250, 322) has shown that when Z-menthone ([a]n about -28°) is treated with 90 per cent, sulphuric acid, a product is obtained which possesses a rotatory power of about [oJd +28°. It appeared probable that this change was due to the racemisation of one of the two asymmetric carbon atoms contained in the ketone, and that, if this were the case, the resulting mixture might be separated into its components by the fractional crystallisation of the semicarbazones obtained from it. In order to ascertain Avhether this could be accomplished, the following experiment was conducted. Fifteen grams of Z-menthone (Kahlbaum) having a rotation of [a]n -28-0° were inverted according to the method employed by Beckmann (Zoc. cit.), when a product was obtained which had a rotation of [a]o +22°. Twelve grams of this were converted into the semicarbazones, which were fractionally crystallised from alcohol. A quantity (96 grams) of a compound melting at 184—186° was thus obtained, which was shown to be Z-menthone semicarbazone, both hy comparison with the latter and by the characters of the regenerated ketone. The mother liquors yielded a substance melting at 126—127° * which crystallised in imperfectly-formed cubes. This was found to be identical with the above-described semicarbazone melting at 125—126°. The ketone regenerated from it was found to boil at 208—209°, had cZ = 0-8988 at 20°/20°, and +42°20' in a 1-dcm. tube, whence [a]o +47-1°. This menthone thus possesses the highest dextrorotatory power that has as yet been observed. Beckmann (J. pr. Chem., 1897, 55, 18), by oxidising Zsomenthol with chromic acid, obtained menthones varying in optical rotation from [a]i) +30° to [a]i, +35°, values considerably lower than that recorded above. The amount of Z-menthone semicarbazone obtained from the above- described “inverted menthone” ([a]o +22°) indicates that it must have contained at least 60 per cent, of Z-menthone ([aji, —28°). The specific rotation of the dextrorotatory constituent of this mixture, calculated from these figures, would therefore be [a]n +97°. It is * The mother liquors from this second semicarbazone yielded a very small quan- tity of a substance which crystallised in fine needles melting at 161—163°, The nature of this compound has not been determined.