— 134 — 



example, can also be produced from the crude terpinene which is 

 obtained when treating terpin hydrate with dilute sulphuric acid (i : 7), 

 by introducing into it hydrohalogen dissolved in glacial acetic acid. 

 The presence of dipentene renders the separation extremely difficult, 

 and for this reason the characteristic addition-products of terpinene 

 have long been overlooked. The constitution of the hydrochlorides is 

 found on the one hand from the regeneration of terpinene, on the 

 other from their easy manner of production from sabinene and thujene, 

 and from v. Baeyer's terpineol of the m. p. 69 . Wallach accepts 

 the following formula, and for the sake of comparison the formula of 

 dipentene dihydrochloride has been placed below it: — 



yCH 2 — CH 2 

 CH 8 — CC1 \cci — CH(CH 3 ) 2 



\ch 2 -ch/ 



Terpinene dihydrochloride (1, 4-dichlorohexahydro-p-cymene) 

 /CH 2 — CH. ? 



/ \ 



CH 3 — CCl \CH— CC1(CH 8 ) 2 



\ch 2 -ch/ 



Dipentene dihydrochloride (1, 8-dichlorohexahydro-p-cymene) 



From the hydrochloride or the hydrobromide, terpinene can be 

 produced in the pure state in the following manner: 10 g. terpinene 

 hydrochloride are heated with 20 cc. aniline until reaction begins, and 

 after adding 20 cc. glacial acetic acid, are distilled over with steam 

 The distillate is shaken with oxalic acid, and again treated with steam, 

 which operation is repeated until the distillate has been freed from aniline. 

 Pure terpinene boils between 179 and 181 (d2o° 0,846; n D 14789), 

 yields without difficulty the nitrosite (m. p. 155 ), and readily absorbs 

 hydrohalogen acids. When terpinene dihydrobromide (m. p. 5 8°) is 

 treated with silver acetate in solution of glacial acetic acid, there is 

 obtained, after saponification of the acetate formed, a-terpineol (m. p. 3 5 ), 

 but in addition to this, cis-terpin (m. p. 1 17 ) and trans-terpin (m. p. 156 

 to 1 57°). The view that according to this result the hydrochlorides 

 of terpinene could yet be identical with the corresponding compounds 

 of dipentene, and that only physical isomerides might here be present, 

 is contradicted by the following experimental results. 



Whilst dipentene dihydrochloride, when shaken with 2 percent, aqueous 

 potash liquor at 50 , readily yields, besides dipentene, a-terpineol, 

 cis-terpin (m. p. 11 7 ), and trans-terpin (m. p. 156 ), there is formed 

 during the same treatment of terpinene dihydrochloride at ioo°, 

 much more slowly, in addition to a large quantity of pure ter- 

 pinene, a new terpineol of the following constants: b. p. 212 to 2 14°; 



