Notes on scientific research. 



151 



latter forms methylheptenone (semicarbazone, m. p. 135°) when oxidized with lead 

 oxide and acetic acid or when its sodium salt is heated in a dry state. The reduction 

 of «./?-dihydroxycitronellic acid leads to an acid Ci H 20 O 4 , the «^-dihydroxyhydro- 

 citronellic acid whose sodium salt produces on heating methylheptanone (isoamylacetone). 



On the maximum tension of camphor vapour see page 118. 



Condensation of p-tolylidenecamphor with p-tolylmagnesiumbromide. — A. Haller 1 ) together 

 with Ramart has studied the effect of p-tolylmagnesiumbromide on p-tolylidenecamphor, 

 whereby the formation of two isomeric di-p-tolylcamphomethanes was to be expected. 

 The viscous condensation product produced, on being distilled in vacuo (15 mm.), a 

 fraction boiling between 100 and 240°, from which a crystalline mixture separated 

 itself which by means of repeated crystallization could be resolved into 2 components, 

 namely p-tolylidenecamphor (melting point 98°) and p-ditolyle (melting point 119 to 

 120°). Two crystalline compounds were isolated from the portions boiling between 

 240 and 265° which gave the melting points of 108° and 98 to 99° respectively. The 

 various products of reaction turn, when heated with alcoholic caustic potash, into a 

 compound melting from 113 to 114°. 



The substance with the melting point 98 to 99° gave [«] D + 75°, that melting from 

 113 to 114° [«] D about +16°. 



For the time being, the authors regard the compound melting at 108° as a mixture 

 of the two substances melting from 98 to 99° and from 113 to 114° respectively. 



Accordingly, the condensation of p-tolylidenecamphor with tolylmagnesiumbromide 

 leads to two isomeric di p-tolylcamphor methanes, just as that of benzalcamphor with 

 phenylmagnesiumbromide produce two isomeric diphenylcamphormethanes. 



Transformation products of nopinone.— In order to explain the relations between 

 polycyclical terpenes to monocyclical ones, their attitude towards sulphuric acid is of 

 paramount importance. In this manner camphor reacts with sulphuric acid producing 

 dihydrocarvone or its product of rearrangement carvenone. According to E. Rimini 2 ), 

 nopinone (I), a ketone, which besides by other means can be prepared from nopinic 



CO CO CO 



H 2 C 

 H 2 C 



CH 

 CH 



H 2 C 

 H 2 C 



CH 2 

 CH 2 



CH C - 



HaC-CH-CHs H 3 CCCH 3 



(II) 2s0propyI-J I -hexanone-4. (Ill) J$opropylidenetv/c?ohexanone-4. 



acid, an oxidation product of /?-pinene, by oxidation with lead peroxide or perman- 

 ganate in a solution of sulphuric acid, produces on being treated with concentrated 

 sulphuric acid at room temperature a mixture of Z-isopropyl-zl 2 -C2/cZohexanone-4 (II) and 

 of ?-£sopropylidenec2/cfohexanone-4 (III). When boiled, however, with diluted sulphuric 

 acid only the former originates. This ketone yields a semicarbazone melting at 201°, 

 whereas J 2 -isopropylhexenone semicarbazone melts at 183°. Jsopropylidene hexanone-4 

 produces acetone and tetrahydroquinone on being oxidized with permanganate. 



!) Bull. Soc. chim. IV. 19 (1916), 219. 

 905. — Journ. chem. Soc. 110 (1916), 1. 655. 



2 ) Gazz.chim. ital. 46 (1916), II. 119; Chem. Zentralbl. 1916, II. 



