G-12.] 



DIPENTENE 



39 



[54 ; F]) and potassium cyanide [172] 

 through pyrotartaric nitrile (Pinner, 

 Ber. 12, 2053) and then as above. 



10. Terpinene ; A 1 ' 4 -Menthadiene. 



CH, 



HC 



(JH 3 



CH 



9 



OIi3 . CH . Cli3 



For constitutional formula see Harries, 

 Ber. 35, 1169. 



NATURAL SOURCES. 



In oil of Ceylon cardamom from 

 Elettaria cardamomum, var. major 

 (Weber, Ann. 238, 107), and in oil of 

 sweet marjoram from Origanum majo- 

 rana (Biltz, Ber. 32, 995). 



NOTE : It is possible that the terpinene does 

 not pre-exist in the oils from these plants, but 

 is formed from some compound in the oils by 

 the heat of distillation (Gildemeister and Hoff- 

 mann, p. 178 : see also Semmler, Ber. 34, 718). 



SYNTHETICAL PROCESSES. 



[A.] Dipentene [9] gives terpinene 

 on treatment with hydrochloric or sul- 

 phuric acid in alcoholic solution (Wal- 

 lach, Ann. 239, 15 ; 35). Limonene 

 gives terpinene when distilled with 

 solid arsenic acid (Genvresse, Comp. 

 Rend. 134, 360). 



[B.] Cineole [40] gives terpinene by 

 the same treatment (Wallach, Ann. 

 239, 22). 



[C.] Terpineol [39] gives terpinene 

 among other products on heating with 

 dilute sulphuric acid (Wallach and 

 Kerkhoff, Ann. 275, 106) : also on boil- 

 ing for some time with oxalic acid 

 solution or with anhydrous formic acid 

 (Ibid. 291, 342). 



[D.] From geraniol [36] through 

 terpin hydrate (see under dipentene [9 ; 

 C]) and the action of boiling dilute 

 sulphuric acid on the latter. 



[E.] From linalool [37] through ter- 

 pin hydrate, &c. (see under dipentene 

 [9 ; D] ; also Bertram, Journ. pr. Ch. 

 45, 601). 



[P.] From carvone [127] through 

 dihydrocarveol by reduction. The latter 

 gives terpinene on boiling with dilute 

 sulphuric acid (Wallach, Kruse, and 

 Kerkhoff, Ann. 275, 113). Dihydro- 

 carvylamine also gives terpinene when 

 acted upon by acid (Wallach, Ber. 24, 

 3991) or by distilling the dry hydro- 

 chloride (Wallach, &c. Ann. 275, 120). 



11. Ltevo-Isoterpene (?), 



NATURAL SOURCES. 



A hydrocarbon corresponding with 

 the above possibly exists in elemi resin 

 from species of Canarium and in the 

 resins from Pinus and Abie* (Kuriloff, 

 Journ. Russ. Soc. 21, 362). 



SYNTHETICAL PROCESS. 



[A.] Terpineol [39] gives isoterpene 

 on heating with acetic anhydride to 

 135-150 (Flawitzky, Ber. 12, 2356). 



NOTE : The synthetical product -was obtained 

 from 1-terpineol acetate prepared by the action 

 of zinc chloride and acetic acid on pinene 

 (Ertschikowsky, Journ. Russ. Soc. 28, 132). 

 The synthesis is thus complete only in so far 

 as the synthesis of 1-terpineol is complete. 

 d-Isoterpene is also said to have been syn- 

 thesised from d-terpineol (Flawitzky, Ber. 20, 

 1961) 



12. Naphthalene. 



H 



HC 



H 



/\ 



C CH 



HC C CH 



V V 



H H 



NATURAL SOURCES. 



According to v. Soden and Rojahn 

 (Pharm. Zeit. 47, 779) this hydrocarbon 

 is contained in certain ethereal oils from 

 clove stems and storax bark. 



Syntheses of naphthalene are given 

 under hydro juglone (90). 



