— 172 — 



Kondakow 1 ), who lays special stress upon the extent to which 

 his investigations have contributed to throw light upon the constitution 

 of the terpinene-derivatives, concludes from the methods of preparing 

 terpinene, as well as from its leading physical and chemical properties, 

 that the hydrocarbon which formed the crystalline nitrosite, m. p. 155 , 

 is a zl 1}4 -menthadiene. It would lead us too far to reproduce Kon- 

 dakow's views, which are not supported by experimental facts, and 

 we therefore refer to the original paper. 



The author obtained a hydrocarbon of the probable constitution 

 of J 1 ' 3 -menthadiene by splitting off 2 molecules of hydrochloric acid 

 from the dichloride of the secondary-secondary diolalcohol, by means 

 of alcoholic potash: b.p. 178 to 181 , d2o° 0,846. This body is optically 

 inactive and gives no solid di-haloid anhydrides. Kondakow has suc- 

 ceeded in reducing the dimethyl thymo-hydroquinone by Sabatier's and 

 Senderens' method and hopes in this way to arrive at terpinene. 



We are indebted to Auwers for a most interesting contribution on 

 the solution of the terpinene problem. This author has continued 

 with F. von der Heyden 2 ) the researches on the synthesis of hydro- 

 aromatic hydrocarbons, which he had begun in collaboration with 

 M. Hessenland. As his raw material he employed methyl - dichloro- 

 methyl-keto-dihydrobenzene (I), prepared from o-cresol by the action 

 of chloroform and alkali. This body was converted into the higher 

 homologues of methyl- dichloro - methyl -keto-dihydrobenzene by acting 

 upon it with magnesium alkyl- iodide (II). JBy means of concentrated 

 sulphuric acid the resultant product was converted into the isomeride (III), 

 and by boiling with alcoholised potash he obtained the corresponding 

 hydrocarbon (IV). By using magnesium isopropyl iodide he obtained 

 Zl 1 ' 3 -menthadiene (a-terpinene). 



I. II. III. IV. 



CH. CHC1 2 CH 3 CHC1 2 CH 3 CHC1 2 CH 3 



\ / \ V \ / I 



c c c c 



hc/ \:=o hc/ \:=o h 2 c/ \:=o h 2 c/ ^ch 



II I II I II II 



HCv s/CH HCv /CH 2 H 2 Cv //CH H 2 Cv //CH 



CH CH C C 



I I I 



CH CH CH 



/\ /\ / \ 



CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 



Decomposition by means of oxidation, and the preparation of the 

 nitrosite (m. p. 155 ) afforded proof that the body in question was 



*) Journ. f. prakt. Chem. II. 79 (1909), 497. 

 2 ) Berl. Berichte 42 (1909), 2404. 



