Notes on scientific research. 



99 



lected in the cooler. After treating the distillate with 5 per cent, soda lye it was once 

 more distilled over metallic sodium. The p-cymene obtained in this way had the 

 following constants: — b. p. 176 to 176.5°; n D12 . 5 o 1.4905. 



Since purified ^-cyrriene is an important solvent Wheeler determined the solubility 

 of some compounds in this substance at different temperatures: 100 g. of ^-cymene 

 dissolved 1.53 g. of ^-camphoric acid at 100°, 113.85 g. of thymol, 6.53 g. of benzoic 

 acid and 0.986 g. of salicylic acid at 25°. 



The author observed further that ^>-cymene was quickly coloured red by an addition 

 02 per cent, of ^-anisidine. Other impurities cause similar colorations, whilst the 

 pure ^?-cymene remains colourless. 



Pinene. — A new partial synthesis of pinene via the pinocamphyltrimethylammonium 

 hydroxide, yielding a pure pinene of b. p. 156° (725 mm.), has been effected by 

 L. Ruzicka and H. Trebler 1 ). They started from pinocamphylamine (I) which was prepared 

 by the catalytic reduction of pinylamine (II); the further synthesis proceeded along 

 the line of the reactions which we describe in the case of bornylene (see page 103 of 

 this Report). The authors could also in this case prepare two isomeric pinocamphyl- 

 trimethylammonium iodides (m. p. 255° and 300 to 301°). In preparing the pinene- 

 nitrosochloride the authors observed, that alcoholic hydrochloric acid yields a product 

 of a higher melting point, 107 to 108°, than that which results when the process of 

 Wallach is employed (m. p. 103°). 



CH-CH 3 



C-CH< 



CHNHs 



CHNH 2 



CH 



(I) ^Pinocamphylamine. 



CH 



(II) Pinylamine. 



Ruzicka and Trebler further report on experiments which were partly failures, 

 undertaken to prepare, from pinonic acid (III), the easily-accessible oxidation product 

 of pinene, the homopinocamphoric acid which was not known so far. In this the 

 authors made the following observations: — 



(1) The ethylpinolate (IV) prepared by catalytic reduction of ethylpinonate yielded with 

 phosphorus pentachloride, in addition to pinocampholenic ester, only little of the desired 

 chloroester (V). They did not succeed in converting this ester into homopinocamphoric 

 acid. In the preparation of ethylpinonate (b. p. about 100° [one third mm.], semi- 

 carbazone m. p. 136°) it was noticed that pinonic acid was, under certain conditions, 

 easily esterified already by very weak alcoholic hydrochloric acid. 



(2) In treating the ethylester of pinonic acid cyanohydrin with phosphorus penta- 

 chloride they did not obtain the expected ester of dehydrohomopinocamphoric nitrile 

 acid, but the aliphatic 2-cyano-6-methyl-2 : 6-heptadiene-5-acetic acid ethylester (VI) 

 which, on saponification, yielded the dicarboxylic acid of constitution (VII). From the 

 latter they obtained, by treatment with acetic acid anhydride in a sealed tube, the 

 intermediary anhydride (VIII) and further the unstable ketone (IX) and carvacrol (X). 

 This reaction represents a new mode of preparing this phenol. By reduction and 



! ) Beteet. ekim. acta 3 (1920), 756. 



