In addition to the two santalols, East Indian sandalwood oil contains two sesquiterpenes, a- and B-santalene, so named by Guerbet.1) a-Santalene shows the following properties:

B. p. 252 to 252,5° (uncorr.), 253 to 254° (corr.); d0o 0,9134; aD - 13,98° (Guerbet).

B. p. 118 to 120° (9 mm.); d20o0,8984; aD - 15°; nD 1,491 Semmler.2)

B-Santalene shows the following properties:

B. p. 261 to 262° (uncorr.), 263 to 264° (corr.); d0o0,9139; aD - 28,55° (Guerbet).

B. p. 125 to 127° (9 mm.); d20o0,892; aD - 35°; nD 1,4932 (Semmler).

According to Semmler, a-santalene is to be regarded as a tricyclic sesquiterpene with one double bond, B-santalene as di-cyclic with two double bonds.

a-Santalene combines with hydrochloric acid to a liquid hydrochloride. With nitrosylchloride a nitrosochloride, m. p. 122°, results, the nitrolpiperidine base of which melts at 108 to 109°. When oxidized with ozone, Semmler obtained the bicyclic eksan-talal (b. p. 112 to 116° (9 mm.); d20o1,00; aD + abt 4°; nD 1,4872) which likewise results upon oxidation of a-santalol.

1) Compt. rend. 130 (1900), 417, 1324; Bull. Soc. chim. III. 23 (1900), 217 and 540.

2) Berl. Berichte 40 (1907), 3321.

B-Santalene adds two molecules of hydrogenchloride with the formation of a liquid dihydrochloride.1) The nitrosochloride exists in two isomeric forms, which melt at 152° and 106° respectively, and to which two nitrolpiperidine bases (m. p. 101° and 104 to 105° respectively) correspond. When oxidized with ozone a di-cyclic aldehyde results.

Hence the two santalenes appear to stand in genetic relationship to the two santalols. The two santalenes can be identified by means of their nitrosochlorides and by their oxidation products with ozone.

Isosantalenes. The hydrocarbons resulting upon dehydration of the santalols are, however, different from the santalenes. From the crude santalol Chapoteaut2) obtained two hydrocarbons, one C16H24, b. p. 260° and another C15H22, b. p. 245°. The hydrocarbons obtained from the two santalols, Guerbet3) named Iso-santalenes and recorded the following properties: a-Isosantalene: b. p. 255 to 256°; aD + 0,2°.

B-Isosantalene: b. p. 259 to 260°; aD + 6,l°.

It is doubtful whether these two hydrocarbons are sesquiterpenes.

Of the lesser known sesquiterpenes the following may here be mentioned:

Atractylene. This sesquiterpene, which has not yet been found in volatile oils, was obtained by Gadamer and Amenomiya4) by the action of dehydrating agents on atractylol, a sesquiterpene alcohol.

B. p. 125 to 126° (10 mm.); d15o0,9154; nD20o1,50893.

The liquid dihydrochloride, prepared from atractylol, when heated with aniline yields a hydrocarbon which differs from atractylene.