Origin and Production The resinous leaf buds of the white birch, Betula alba, L, contain a relatively large amount of an agreeably smelling, balsamic oil, which was first prepared by H. Haensel'). Upon distillation, the buds yield 4 to 6,5 p.c. of oil.
1) Loc. cit.
2) Compare also E. Kremers and Martha M. James, Pharm. Review 16 (1898), 130.
Properties 2). Oil of birch buds is a yellow, somewhat viscid liquid, which, even at room temperature, is often permeated with crystals of paraffin. Upon cooling the oil at first separates paraffin crystals, finally it congeals to a solid mass. d16o0,962 to 0,979; aD - 2 to - 14°; A.V.I to 4; E. V. 35 to 75; E. V. after acetylation 140 to 180. Soluble in 1 to 2 vol. of 80 p.c. and in 0,25 vol. of 90 p.c. alcohol. At times the solution is clear, frequently, however, paraffin separates. The latter separation always takes place upon the addition of more solvent.
Composition. According to H. von Soden and F. Elze3) the oil contains a sesquiterpene alcohol which they have designated betulol. For the isolation of the betulol its acid phthalic ester was prepared. It results readily when the oil, in benzene solution, is heated with phthalic anhydride. The pure betulol obtained by saponification of the phthalic acid compound with alcoholic potassium hydroxide had the following constants:
B.p. 138 to 140° under 4 mm., 284 to 288° under 743 mm. pressure with partial decomposition; d15o0,975; aD - 35°; soluble in 3 parts of 70 p.c. alcohol. Its composition is presumably C15H240.
When boiled with acetic anhydride, betulol is acetylated quantitatively. The acetate boils at 142 to 144° (4 mm.); d15o 0,986. The content of free betulol of the oil investigated was about 47 p.c.
Another oil contained 73,2 p.c. of total betulol, of which 29,6 p.c. was esterified and 47,1 p.c. free. The esterified betulol is partly bound to acetic acid, partly to formic acid4).