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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    thus probable that the above-desci’ibed dextrorotatory menthone did not possess its full degree of optical activity, and that the difference between the calculated value ([a]o +97°) and the figures actually obtained ([a]o +47’1° to +48‘6°) may be attributed to racemisation having taken place during the liberation of the ketone from its semi- carbazone. Since the menthone molecule contains two asymmetric carbon atoms, ordinary ^menthone must be represented by either the configuration - - or - +. On treatment with sulphuric acid, one of these asym- metric carbon atoms, without doubt the one situated in the a-position to the keto-group, undergoes racemisation, and it has been shown that the resulting mixture consists of ^menthone, together with a second menthone possessing a rotatory power of opposite sign but of greater value than that of the former ketone. It follows from this that ordinary 7-menthone must be represented by the second con- figuration, namely, —H, and that on treatment with sulphuric acid the carbon atom possessing a Isevorotatory power undergoes racemisa- tion. The d!-menthone contained in hedeoma oil, and also in Beck- mann’s “ dextro-menthone ” {Annoden, 1889, 260, 322), must therefore be represented by the configuration + +. As this ketone is not the optical antipode of ^-menthone, it would seem advisable to denote it by some distinctive name, such as d-isomenthone.* The two other possible menthones, possessing the configurations and H— respectively, both of which are apparently at present unknown, would then be designated respectively as 7-isomenthone and cf-menthone. Fraction 217—224°.—^The amount of this fraction was 43 grams: 0-1616 gave 0-4638 COg and 0-1565 HgO. 0 = 78-3 ; H= 10-8. d 20°/20° = 0-9257; an +23°0' in a 1-dcm. tube. A portion of this fraction was treated with semicarbazide and the resulting semicarbazones fractionally crystallised, when it was found to consist of the constituents of the preceding fraction, but containing a larger proportion of pulegone than the latter. Fraction 220—240°.—This amounted to 10 grams : 0-1083 gave 0-3125 CO.^j and 0-1052 HgO. 0 = 78-7 ; H = 10-8. d 20°/20° =0-9270 ; op + 12°4' in a 1-dcm. tube. This consisted of pulegone and the constituents of the fractions of higher boiling point. * This nomenclature is in accordance with that adopted by Aschau (Chemie der alicyklischen Verbindungen, 1905, p. 667), who designated the “d-menthone” of Beckmann as d-fsomenthone, but recognised that this is a mixture of Z-menthone and a hitherto unknown dextrorotatory menthone which, wlien isolated, would properly receive the n&me d-womeuthon