38 



HYDROCARBONS 



[9-G. 



221 ; Bertram and Walbaum, Arch. 

 Pharm. 231, 290; SchimmeFs Ber. Oct. 

 ] 892 ; April, 1893) ; in American oil of 

 spearmint from Mentha viridis (Power, 

 quoted by Gildemeister and Hoffmann, 

 p. 852; in Russian oil, SchimmeFs 

 Ber. April, 1898; Ch. Centr. 1898, 1, 

 991); in Russian peppermint oil (Andres 

 and Andreef, Ber. 25,609); in American 

 peppermint oil (Power and Kleber, 

 Pharm. Rund. 12, 157 ; Arch. Pharm. 

 232, 639) ; in oil of cascarilla (see 

 above under dipentene ; also Fendler, 

 Arch. Pharm. 238, 671); in oil of rue, 

 probably Algerian (Power and Lees, 

 Trans. Ch. Soc. 81, 1590); in the oil 

 of Bystropogon onganifolius, Teneriffe 

 (SchimmeFs Ber. Oct. 1902; Ch. Centr. 

 1902, 2, 1208). 



The oil from the leaves of Verbena 

 tripJiylla (Grasse) probably contains 

 1-limonene (Theulier, Rev. gen. de China. 

 6, 324). A limonene is present in the 

 American oil of cedar leaves from Juni- 

 perus virginiana (SchimmeFs Ber. April, 

 1898; Ch. Centr. 1898, 1, 990). 



SYNTHETICAL PROCESSES. 



[A.] From terpineol [39] by heating 

 the latter with acid potassium sulphate 

 to 190 (Wallach, Ann. 230, 258; 275, 

 104; 291, 362). 



[B.] Cineole [40] gives a hydro- 

 chloride which yields dipentene on dry 

 distillation (Hell and Stiircke, Ber. 17, 

 1971; Hell and Ritter, Ibid. 1979; 

 Wallach and Brass, Ann. 225, 298). 

 Also from cineole by heating with 

 benzoyl chloride or by combining with 

 hydrogen iodide and then eliminating 

 hydrogen iodide from the dipentene 

 dihydriodide thus formed (Wallach and 

 Brass, loc. cit. ; Wallach, Ann. 23O, 



355)- 



[C.] Geraniol [36] by the action of 

 dilute mineral acids gives terpin hydrate 

 (Tiemann and Schmidt, Ber. 28, 2137). 

 The latter on heating with acid potassium 

 sulphate at 200 gives dipentene (Wal- 

 lach, as under A above). 



[D.] Linalool [37] also gives terpin 

 hydrate by the action of mineral acids 

 (Tiemann and Schmidt, foe. cit.}. Formic 

 acid acts on 1-linalool with the forma- 



tion of dipentene and terpinene (Ber- 

 tram and Walbaum, Journ. pr. Ch. [2] 

 45, 601; Stephan, Ibid. [2] 58, 109: 

 see also Charabot, Bull. Soc. [3] 23, 

 189). 



[E.] From carvone [127] through its 

 oxime and dihydrocarvylamine by re- 

 duction. The hydrochloride of the 

 latter gives dipentene among other pro- 

 ducts on treatment with sodium nitrite 

 (Wallach, Kruse, and Kerkhoff, Ann. 

 275, no). Dihydrocarvylamine can 

 also be obtained from carvone by heating 

 with ammonium formate (Leuckart and 

 Bach, Ber. 2O, 105; Wallach, loc. cit. 

 120; Ber. 24, 3984). 



d-Carvone can be reduced by sodium 

 to dihydrocarveol and the latter con- 

 verted into the xanthic acid dihydro- 

 carvyl methyl ester by means of carbon 

 disulphide and subsequent methylation 

 of the sodium salt. The methyl dihydro- 

 carvyl xanthate on dry distillation gives 

 1-limonene (Tschugaeff, Ber. 32, 3332 ; 

 33, 735). 



[F.] From normal or isopropyl alcohol 

 [15 ; 16] and potassium cyanide [172] 

 through the nitrile of pyrotartaric acid 

 by the interaction of propylene bromide 

 and the cyanide (S impson, Ann. 121, 1 60) 

 and ft - methyltetramethylenediamine 

 by reduction (Oldach, Ber. 20, 1654). 

 The diamine is converted into 3-^- 

 methylpyrrolidine by the dry distillation 

 of the hydrochloride ([bid. 1657), the 

 latter base into /3-methyl-N-dimethyl- 

 pyrrolidylammonium iodide; the latter 

 distilled with solid potash gives a base 

 which combines with methyl iodide to 

 form/3-methyl-N-trimethylpyrrolidylam- 

 monium iodide, and the latter on distilla- 

 tion with solid potash gives trimethyl- 

 amine and isoprene [CH 2 : C(CH 3 ) . CH : 

 CH 2 ] (Euler, Ber. 3O, 1989). Isoprene 

 polymerises on heating to 250 or by 

 the action of dilute or alcoholic sulphuric 

 acid with the formation of dipentene 

 (Wallach, Ann. 227, 295 ; Bouchardat, 

 Comp. Rend. 89, 1217). 



NOTE : All generators of propylene thus be- 

 come, with potassium cyanide, generators of 

 dipentene. 



From glycerol [48] through 

 allyl chloride (see under benzyl alcohol 



