LXXVI.—The action of nitrosyl chloride on pinene
Journal of the Chemical Society Transactions
15, 554) in which, in conjunction with Mr. Shenstone, I first described the application of nitrosyl chloride to the purpose of classifying the terpenes, attention was drawn to the apparent connection between the optical activity of the hydrocarbon operated on and the yield of nitrosochloride. It was found that terpenes of high rotatory power gave a much smaller product than others apparently identical in other respects, but having less action on the polarised ray. Von Baeyer having shown
... having shown (Be?.., 1895, 28, 648) that pinene nitrosochloride is a bimolecular compound with the formula (C,oH"*NOC1)2, it occurred t o me that the inferior yield of nitrosochloride by the more strongly rotating varieties of the hydrocarbon was due to the destructive effect of heat generated in the process of inversion of one-half of the compound as soon as formed, and that by using a mixture of d-and I-pinenes in due proportions the bimolecular compound would at once be produced by simple combination of the two semi-molecules without further change in either of them, and a larger product would rcsult. This turns out to be the case. When to pinene from American turpentine, diluted with half its volume of chloroform and cooled to about 0", is added very gradually a solution of nitrosyl chloride in chloroform, an intense blue coloration is observed on the addition of each drop of the reagent. The colour quickly fades and a white, crystalline precipitate soon begins to form. A similar, though less intense, blue colour is produced when ethyl or amyl nitrite together with hydrochloric acid is employed, as in the process introduced by Wallach (Annalen, 1888,245, 251) . When the blue colour is no longer produced, the liquid diluted with about three times its volume of 84 per cect. alcohol yields a precipitate which, after being washed with alcohol and dried at about 50°, amounted in a series of experiments pretty uniformly to 31-32 per cent. of the pinene. The specimen used had a rotation of about + 7" in a 200 mm. tube. When the d-pinene was replaced by I-pinene of greater rotatory power (-57O48' in 200 mm.), the yield was much less and never exceeded 20 per cent. of the pinene employed. A specimen of pinene from the turpentine of Pinus Khasyana, which has a specially high rotatory power ( + 80'41'