— U3 — 



a secondary and a tertiary compound. They have recently gone 

 further into this question by examining the behaviour of the above 

 hydrocarbons and of sabinene towards haloid hydracids, and they have 

 now arrived at the conclusion that the occurrence of liquid dihalo- 

 hydrogen compounds, which are particularly formed during this treat- 

 ment from thujene (obtained from thujyl haloid anhydrides), must be 

 attributed to the high-boiling portions mixed with thujene, i. e. iso- 

 thujene (Semmler's tanacetene). For this reason the solid dihaloid 

 anhydrides which can be converted into trans-terpin derivatives, are 

 formed from the true dicyclic thujenes. Iso thujene can be recovered 

 from the liquid dihalogen compounds, by splitting off two molecules 

 haloid hydracid; but it does not appear to be identic with the tana- 

 cetene, thujene, and isothujene from the amines. Possibly it is here 

 a question of mixtures of isomerides. 



Now with regard to the formation of the dihalogen compounds 

 of thujene (from the xanthogenate), it may possibly be explained most 

 simply by accepting the presence of admixed isothujene. The latter 

 may be formed by isomerisation from thujene. To the last-named, the 

 dextrorotatory hydrocarbon with lower boiling point and smaller specific 

 gravity, the authors give the following constitution: 



CH = CH 



/ \ 



CH 3 . CH 



\ 

 whilst the following formula would then belong to the isomeride: 



CH — CH, 



f \ 



CH 3 .C 



\ 



On oxidation with potassium permanganate, the authors obtained 

 from the first-named more stable hydrocarbon, homotanacetone dicar- 

 boxylic acid of the melting point 146 to 147 ; from the isomeride 

 with the higher boiling point, i. e. the isothujene, they obtained 

 a- and /?-tanacetogene dicarboxylic acids (melting point 14 1°, and 11 6° 

 to 1 1 7 ). Later in his work, Kondakow refutes the arguments 

 which Tschugaeff x ) and Semmler 2 ) bring forward against Konda- 

 kow' s thujone formula, and endeavours to explain by means of his 

 formula the conversion of tanacetone into carvotanacetone, and also 

 that of a- tanacetone ketocarboxylic acid into the jS-form. 



Contrary to Kondakow and Skworzow, Tschugaeff 3 ) explains 

 in a subsequently published work on thujone derivatives, the formation 



x ) Chem. Ztg. 27 (1903), 970. 



2 ) Berl. Berichte 36 (1903), 4367. 



3 ) Berl. Berichte 37 (1904), 1481. 



