— 175 — 



In his researches intended to elucidate the constitution of terpinene, 

 Wallach has shown that the terpinene obtained from terpinene-dihydro- 

 chloride, pinene and sabinene-hydrate, contains ^-terpinene (zJi ? 3-dihydro- 

 cymene) and y- terpinene (zfi j4 -dihydrocymene) 1 ). It was therefore a 

 matter of interest for Wallach to investigate also the structure of 

 terpinene of different origin 2 ). One of the longest-known modes of 

 formation is that from bihydro-carvylamine. Dry distillation of bihydro- 

 carvylamine hydrochloride yielded a hydrocarbon boiling at 174 to 17 8°, 

 which, when oxidised, only gave very little a, a'-dihydroxymethyl-wfl- 

 propyladipic acid, m. p. 189 , and only traces of the erythritol which 

 melts at from 236 to 23 7 . The preparation contained, therefore, 

 but little terpinene. When bihydro-carvylamine phosphate, which was 

 first prepared by Harries, was distilled, the result was a product boiling 

 principally between 176 and 179 . This consisted for the greater part 

 of a-terpinene; for in the process of oxidation considerable proportions 

 of a - a'- dihydroxymethyl - /^propyladipic acid, together with a little 

 erythritol were obtained. In the preparation from the phosphate, 

 therefore, a further -reaching displacement of the ethylene -bond in 

 the bihydro-carvylamine has ensued than in the case of the dry 

 hydrochloride. 



It will probably also be difficult to obtain a uniform- product by 

 the method recommended by Semmler for the preparation of a-terpinene 

 i. <?., by reduction of monochloro terpinene (chloro-carvenene). By 

 allowing the calculated quantity of phosphorus pentachloride to act 

 upon diluted carvenone at a low temperature oxygen and dichlorinated 

 bodies may easily be formed, while an excess of phosphorus penta- 

 chloride or increased temperature may favour the formation of cymene 

 derivatives. This view of Wallach was confirmed by the fact that 

 Klages and Kraith on the one hand, and Semmler on the other make 

 different statements as to the monochloroterpene which resulted from 

 carvenone. Wallach's experiments show that even when the work is 

 conducted with the utmost care, preparations with very different pro- 

 perties are obtained. 



The carvenone which was used in the experiments was carefully 

 purified from the semicarbazone and treated with phosphorus penta- 

 chloride in petroleumether solution according to Semmler's indications. 

 But the monochloride was by no means so readily formed as was to be 

 expected from Klages 5 and Kraith's statements. Wallach did in fact 

 succeed in obtaining fractions with the properties of the mono-chloride 

 described by Semmler and Klages, but ultimate analysis of the product 

 of investigation gave unsatisfactory figures, so that it was to be in- 



*) Liebigs Annalen 362 (1908), 285; Report November 1908, 174. 

 2 ) Liebigs Annalen 368 (1909), 13. 



