V. On the constitution of capryl alcohol from castor-oil

Abstract

There is perhaps no other compound known which has been so often and so fully investigated by different chemists, and yet whose constitution is clouded in so much obscurity, as the alcohol which is obtained by distilling castor-oil soap with caustic alkalies. From the time of its discovery until recently, this compound has been alternately considered by one investigator to be capryl or octyl alcohol, and by another to consist of œnanthyl or heptyl alcohol. As a proof that it is capryl alcohol, Bouis states that, by the moderate action of nitric acid, a small quantity of caprylic acid is produced, the greater part of the alcohol, however, being oxidized to lower members of the fatty acid series; and Kolbe concludes, from the formation of these acids, that it is a secondary or isoalcohol, probably methyl-hextl carbinol, C { CH 3 C 6 H 13 H OH. As I shall show in this paper, Kolbe’s view is correct; by moderate oxidation, the alcohol loses two atoms of hydrogen, and is converted into the corresponding acetone, methyl œnanthol, the same compound which is generally obtained as a byeproduct in the preparation of the alcohol. The alcohol which I used was prepared by distilling a mixture of castor-oil soap and caustic soda in a flask of thin copper-sheeting as quickly as possible. The distillate was repeatedly rectified over fused caustic potash, the portion boiling below 200° C. only being collected. The alcohol was isolated from this liquid by fractional distillation; its corrected boiling-point was 181° C. The portions having a lower boiling-point consist of hydrocarbons, which combine with bromine, probably members of the olefine series, amongst which octylene, boiling at 125° C., preponderates. A considerable quantity of liquid distilled above 160°, the boiling-point remaining somewhat constant at 170° C. Neither this fraction nor any other distillate contained an acetone, as none combined with hydrogen-sodium sulphite. According to Chapman, the liquid boiling at 170° consists chiefly of heptyl alcohol. In order to isolate this alcohol, I acted upon the liquid boiling between 160°-175° with iodine and phosphorus. The product, subjected to fractional distillation, was found to consist of isoctyl iodide, boiling at 210°-215°, and of hydrocarbons, distilling below 160°; the portion which came over between 160° and 210° was very small, and diminished after each further distillation. This shows that no heptyl alcohol was present, and that the original liquid boiling at 170° was a mixture of isoctyl alcohol and hydrocarbons, which could not be separated by simple fractioning. To obtain the oxidation products of isoctyl alcohol, I acted upon it with a solution consisting of 3 parts of sulphuric acid, 2 parts of potassium bichromate, and 10 parts of water, the reaction being moderated by surrounding the vessel with cold water. As soon as no further action was observed, the liquid was distilled. The distillate consisted of an aqueous liquid, which had a slight acid reaction, and a light oily fluid; it was neutralized with sodium carbonate, and the oil treated again with the oxidizing mixture, which, however, had hardly any action upon it m the cold. This oily liquid is methyl œnauthol; it has the characteristic odour of that compound, and when shaken with a concentrated solution of hydrogensodium sulphite, solidifies to a mass of pearly white crystals. These were dried between blotting-paper, and decomposed by a dilute solution of cans soda. The oil which separated was dried over calcium chloride; it distilled completely between 170°-172°, the boiling-point of methyl œnantnol being 171°.