140 Report of Schimmel § Co. 1922. 



According to another process devised by L. Schmidt 1 ) the bornyl and isobornyl 

 esters of organic acids are obtained in a good yield and free from by-products when 

 these acids are heated with pinene or pinene-containing oils with an addition of boron 

 trioxide. This latter reagent acts as a general condensing agent for pinene and organic 

 acids by which pinene is esterified in a short time quantitatively even in open vessels. 

 It is said to offer particular advantage to act on the mixture with boric, metaboric, 

 or tetraboric acids on the anhydrides of the organic acids. For instance, 13.6 pts. of 

 pinene or turpentine oil, 9 pts, of glacial acetic acid, and 1 pt. of boron trioxide are 

 heated to its the boiling point under a reflux tube, until the ester content increases 

 no more. The ester mixture is washed with water and fractionated in vacuo and yields 

 on saponification with alcoholic potash pure borneol -f- isoborneol with a m. p. of 197 

 to 199°. The unchanged boron trioxide can be used again. 



The process may be modified 2 ) by substituting the boron trioxide by so-called 

 mixed anhydrides of boric and of organic acids, such as boric acetic anhydride. This 

 mixed anhydride, a simple additional product of the formula: — 



3 *~£°>0 4-B 2 3 = 2B(OCOR) 3 



is preferably prepared in the course of the reaction. For instance, 136 kg. of pinene, 

 60 kg. of glacial acetic acid, 10.2 kg. of acetic anhydride, and 2.3 kg. of boron trioxide 

 are heated together for several hours on a water-bath, the reaction-product is rinsed 

 with water as soon as the ester- content has reached a maximum, and the acetates of 

 borneol and isoborneol are obtained by fractional distillation. Saponification yields 

 a mixture of pure borneol and isoborneol, m. p. 197 to 198°. 



F. Martin 3 ) started some experiments on the acetylation of borneol and isoborneol. 

 His investigation culminated in the result that in estimating borneol or alkylborneol 

 the alcohol must be heated for three hours with 3 parts of acetic anhydride and some 

 sodium acetate up to 145 to 150°. With less time, or less acetic anhydride, acetyl- 

 ation remains incomplete, as Martin states. (The acetylation was performed in an 

 oil bath at a temperature close to the boiling point.) 



Contrary to these statements it is quite sufficient when in the quantitative acetyl- 

 ation of borneol, equally so of geraniol, menthol, and santalol, 10 ccm. eacti of the 

 alcohol and of acetic anhydride are boiled for one hour with 2 g. of sodium acetate. 

 Years ago 4 ) we established, by way of experiment, the correctness and practicability 

 of this method. 



According to L. G. Wesson 5 ), \sobornyl ester and camphene are obtained by heating 

 a mixture of a carboxylic acid and of pinene hydrohalide with some zinc, the proportion 

 of which not exceeding 5 per cent, of the pinene hydrogen halide employed. 



Carvomenthol. — When reducing a-phellandrene nitrite with sodium and alcohol, 

 Wallach and Herbig 6 ) had obtained, in addition to tetrahydrocarvone (carvomenthone) 

 and tetrahydrocarvylamine, Retrahydrocarveol (Z-carvomenthol), but they abstained from 

 examing the resulting alcohol for optical isomerism. V. Paolini 7 ), on repeating these 

 experiments, found that two isomeric forms of Z-carvomenthol are generated in the 



*) Germ. Pat. Appl. Sch. 50927, Oct. 3, 1921. — 2 ) Germ. Pat. Appl. Sch. 53704, Oct. 3, 1921. Add. to 

 Appl. Sch. 50927. — 3 ) Journ. de Pharm. et Chint. VII. 23 (1921), 168. — 4 ) Report April 1910, 155. — 

 3 ) U. S. Pat. 1 372382, March 22, 1921. As per Chem. ZentralU. 1921, II. 1063. — 6 ) Liebig's Annalen 287 (1895), 

 378. — ') Rend, della R. Accad. dei Lined 30 (1921), 265. As per a separate copy kindly forwarded to us. 



