— 164 — 



Attempts to arrive at a- or /J-pinene by the abstraction of water 

 did not lead to the desired result, owing to this behaviour of homono- 

 pinol; on the contrary, there were obtained, by means of 85 per cent, 

 formic acid, terpenes which gave the terpinene-reaction (nitrite m. p. 1 53 ), 

 the terpinolene-reaction (tetrabromide m. p. 112 to 11 5 ) and the 

 dipentene-reaction (?). From this it may be assumed that during 

 the treatment with formic acid first of all terpin hydrate was formed, 

 which then split up into the known decomposition-products dipentene, 

 terpinolene, terpinene, and terpineol. The action of dry agents splitting 

 off water, such as zinc chloride, potassium bisulphate, and soda-lime, 

 on homonopinol, led to mixtures of terpene-like hydrocarbons which 

 it has not yet been possible to identify. 



The treatment of homonopinol with hydrogen chloride in glacial 

 acetic acid solution yielded dipentene dihydrochloride 



CH 9 CH 9 



H 3 C • C1C< >CH . CC1 • (CH 3 ) 2 



CH 2 CH 2 

 whilst the action of phosphorus pentachloride in ligroin solution in 

 the cold produced the chloride of homonopinol C 10 H 17 C1. It boiled 

 at 95 to 105 (13 mm. pressure) or 200 to 205 at atmospheric 

 pressure, with loss of hydrochloric acid, and consequently differs 

 completely from pinene hydrochloride. This is a fresh proof that 

 in adding hydrogen chloride to dry pinene, in the first phase not 

 the double bond is dissolved, but the tetracyclic ring is broken up. If the 

 glacial acetic acid solution of the chloride is saturated with hydro- 

 chloric acid, dipentene dihydrochloride is also formed. With amyl 

 nitrite and nitric acid, homonopinol chloride yields a chlorinated 

 nitrosate. 



Analogous to homonopinol, Wallach produced from nopinone 

 and ethyl magnesium iodide ethyl nopinol C u H 20 O (m. p. 43 to 45 , 

 b. p. 219 to 22^°), which on heating with formic acid yielded, with 

 loss of water, homologous terpenes, and on shaking with 5 per cent, 

 sulphuric acid was converted into a homologous terpin hydrate 

 C n H 22 2 + H 2 (m. p. 75 to 76 ). 



By saturating ethyl nopinol x ) with hydrohalogenides in glacial acetic 

 acid solution, or by treating homo-cisterpin hydrate in glacial acetic acid 

 solution with hydrohalogenides, the corresponding dihalogen derivatives 

 were formed: dihydrochloride of the m. p. 63 to 64 , dihydrobromide 

 of the m. p. 82 to 84 , dihydriodide of the m. p. 63 to 64 . From the 

 dihydrochloride there was obtained by abstraction of hydrochloric acid by 

 means of aniline, the hydrocarbon C n H 18 (b. p. 201 to 202 ; d 0,8545; 



*) Nachr. K. Ges. Wiss. Gottingen 1907, Meeting of 20. July. 



