This secondary alcohol occurs in the oils of the "Peppermint" group of Eucalypts, and although several members of this group give an oil containing only a comparatively small amount of piperitone (the peppermint ketone of Eucalyptus oils), yet a fair quantity of an alcohol - other than terpineol or geraniol - is present. This investigation showed this alcohol to be the corresponding one to piperitone, and is, therefore, named piperitol. It is an unsaturated alcohol.

Although it occurs naturally in a number of these oils, yet it has not, so far, been possible to form it by the reduction of the ketone, the reduction product, with sodium amalgam particularly, consisting of a solid dimolecular ketone of quite a definite character. (See also the article on piperitone in this work.)

Experience had shown us that one of the best oils for the preparation of this alcohol was that derived from E. radiata, and for this purpose material for distillation was obtained from Hill Top, New South Wales, in November, 1919. The yield of oil was 2.9 per cent. The oil of this Eucalypt consists very largely of phellandrene, and the leaves have the phellandrene venation particularly well-defined.

That ketonic and alcoholic bodies were only present in small amount is indicated from the specific gravity of the crude oil, this being only 0.8643 at 150 C. It was thus fortunate that the yield was so good, particularly as it was necessary to employ a considerable quantity of oil in order to prepare sufficient alcohol for investigation.

The crude oil was first distilled and the portion which came over below 185° C. removed. The remainder was repeatedly distilled under reduced pressure until finally a fraction boiling at 100-1030 C, at 10 millimetres was obtained. This had specific gravity at 15° C. = 0.9326; rotation aD - 2870; refractive index at 200 = 1.4780.

As this fraction contained piperitone, it was removed by agitating with a solution of normal sodium sulphite; the ketone thus recovered in a pure condition, represented 17 per cent. of the fraction. It had all the characters of piperitone and on reduction with sodium amalgam in alcoholic solution gave the solid dimolecular ketone melting at 149-150° C.

The unabsorbed portion was again refractionated, when an oil boiling at 95-96° C. at 10 millimetres was obtained. This had: -

The molecular refraction calculated for a C10Hl8O alcohol with one double bond is 47.14; found 47.04.

It is thus apparent that the lævo-rotation of the alcohol was - after distillation - greater than that of the corresponding ketone, but this may be partly due to the lowering of the optical rotation of piperitone under repeated distillation.

A portion of the alcohol was oxidised in the cold by the potassium bichromate method; when the reaction was complete the product was steam-distilled, the oil separated and agitated with a solution of neutral sodium sulphite in the cold, until practically the whole was absorbed. The regenerated product had all the characters of piperitone, and gave the solid dimolecular ketone on reduction with sodium amalgam. The piperitone thus formed had specific gravity at 15° C. = 0.9390; rotation aD - 24.0°; and refractive index at 20° = 1.4832.