Composition. The statements recorded with regard to the composition of vetiver oil vary considerably and cannot always be harmonized. This is due in part to the difficulty of the investigation because of the high boiling point and viscid character of the oil. The confusion is further attributable to the circumstance that no well-defined crystalline derivatives have thus far been obtained from its constituents.
E. Theulier2) restricted his investigations to a comparison of the properties of two oils, one distilled at Grasse, the other in Reunion: viz. of the boiling temperatures under a pressure of 25 mm. and of the other properties of the corresponding fractions.
According to Franz Fritzsche & Co. 3) vetiver oil is said to contain ketones which can be separated by means of their noncrystalline semicarbazones and oximes from the other constituents. These ketones (vetirone or vetiverone) are said to be mixtures of several isomers which boil at about 149 and 154° (10 mm.). d15o about 0,990. Their analysis revealed the empirical formula C13H220. According to the investigations made by the same firm4), the oil contains in addition to the ketones two alcohols (vetirols or vetiverols) which can be isolated as the acid phthalic esters. The one boils between 150 - 155° (10 mm.),
1) Bull. Imp. Inst. 10 (1912), 32.
2) Bull. Soc. chim. III. 25 (1901), 454.
3) Germ. Pat. 142415 (1902).
4) Germ. Pat. 142416 (1902).
P. Genvresse and G. Langlois1) have shown the presence of two constituents in vetiver oil which are, however, of no importance so far as the odor is concerned. The two oils examined were obtained from Reunion and from Grasse. Both oils contained the same substances but in different proportion, the Reunion oil containing much more sesquiterpene than the other. The neutral Reunion oil had a specific gravity of 0,993 (20°) and an optical rotation of +23°43' (in alcoholic solution). The Grasse oil, which had an acid reaction, had a specific gravity of 1,012 (20°), and an optical rotation of + 27°9'. Upon steam distillation but 1/3 of the total oil passed over and of this a part was relatively lighter than water, the other part heavier. The former consists principally of a sesquiterpene C15 H24, vetivene, a colorless and odorless liquid boiling at 262 to 263° (740 mm.) or at 135° (15 mm.). It has a specific gravity of 0,932 (20°) and an optical rotation of + 18° 19'. It absorbs 4 atoms of bromine, becoming blue, but does not solidify. The denser portion of the oil consists, in the main, of a sesquiterpene alcohol C15H260, the vetivenol, a viscid, light yellow, odorless substance with the following physical constants: b. p. 169 to 170° (15 mm.), d20o 1,011; aD + 53° 43' (in alcoholic solution). With acetic acid anhydride, the alcohol yields an acetate. When acted upon with anhydrous oxalic acid, vetivene, the sesquiterpene mentioned above, is produced. In addition to vetivenol, the distillation residue contains an acid C15H2404 or a mixture of acids. It is a viscid mass which becomes brown upon exposure to air and yields a soluble potassium salt. Genvresse and Langlois are of the opinion that the bearer of the odor of the oil is an ester of this acid with vetivenol, an ester that is readily saponifiable even with water. In connection herewith it should be mentioned that Schimmel & Co.2) have observed crystals of palmitate of zinc in a vetiver oil which had been kept for a long time in a zinc container. Hence the conclusion may be drawn that palmitic acid is a constituent of vetiver oil.
1) Compt. rend. 135 (1902), 1059.
2) Bericht von Schimmel & Co. April 1899, 50.
Bacon1) also has studied the acids of vetiver oil. Upon saponification, 100 g. of oil yielded 19 g. of an acid mixture that possessed a fatty acid odor. After distillation in vacuum, 40 p. c. of a light yellow, viscid acid were obtained. It had the odor of oleic acid and boiled between 200 and 205° under 4 mm. pressure. The analysis of the sodium salt revealed the formula C16H2402.
As already pointed out, Genvresse and Langlois2) attribute the typical vetiver odor to the ester of the acid C15 H24 04 with vetivenol, an alcohol C15H260. With this opinion Bacon could not agree, since the oils remaining after saponification revealed a strong vetiver odor. Upon fractionation of the saponified oil, the odor was observed in the middle and higher fractions (b. p. 137 to 140° and 140 to 145° under 12 to 15 mm. pressure), also in the semisolid, tar-like residue, but not in the lower fraction (b. p. 125 to 133°). From another sample of vetiver oil, Bacon obtained upon saponification, a large amount of benzoic acid.
According to the more recent investigations by F. W. Semmler, F. Risse and F. Schroter2), the formulas assigned by Genvresse and Langlois to vetivenol and the acid are not correct. The former, it is claimed, has the composition C15H240 and the latter the composition C16H2202.
The authors examined an oil distilled by Schimmel & Co., which had the following properties: d20o 1,0239; aD + 31°; nD20o 1,52552. 400 g. were distilled under a pressure of 12 mm. and thus resolved into four fractions, viz.: A. b.p. 129 to 175°, 23%, B. b.p. 170 to 190°, 34%, C. b.p. 190 to 250°, 8%, D. b.p. 250 to 300°, 30%.
By means of a second distillation, fraction D was resolved into two parts: a) b.p. 138 to 260° (13 mm.), 28 %, b) b.p. 260 to 298° (13 mm.), 62%.
According to analysis fraction D, b consisted of an ester C30 H44O2 viz. of the acid C15H2202 and the alcohol C15H240. The free alcohol has the following properties: b. p. 170 to 174° (13 mm.); d20o 1,0209; aD + 34°30'; nD 1,52437; mol. refr. found 65,94, computed for C15H240 66,00. Hence vetivenol must be regarded as a tricyclic alcohol with a single double bond. The acid C15H2202 boils between 202 and 205° (13 mm.), is tricyclic and is named vetivenic acid by the authors. The boiling point of the methyl ester lies between 170 and 173° (18 mm.): d20o 1,0372; aD + 42 12'; nD 1,50573; mol. refr. found 71,05; computed for C16H2402/"71,31.
1) Loc. cit.
2) Berl. Berichte 4o (1912), 2347.