472 THE CHEMISTEY OF ESSENTIAL OILS
Schimmel & Co. have isolated dextro-a-terpmeol from the oil, and
also an alcohol not previously found naturally, which they identified as
methyl-heptenol.
1
This body has the following characters :—Specific gravity 0'8579
Optical rotation - 1° 34'
Refractive index 1-44951
Boiling-point 178° to 180°Schimmel & Co. in 1908 isolated a body possessing the formula
C 1 0H 18 O 2 from this oil. They have since identified it as linalol monoxide,
Identical with the body prepared by Prileshaeff
2
by the oxidation of
linalol by means of benzoyl hydrogen peroxide.
Linalol monoxide is somewhat viscous and is also clearly differentiated
from linalol by its mouldy odour, which recalls that of fenchyl alcohol
and of camphor. As its boiling-point is only 3° to 4° lower than that of
linalol, it is impossible, in view of the very small extent to which it occurs
in the oil, to prepare it in the pure form by fractionation. It is, however,
possible to obtain ID pure, although at a considerable loss of material, by
repeatedly oxidising the fractions containing linalol of high specific gravity
i
vith 0
- 5 per cent, permanganate solution at ice temperature, each time
driving off the unattacked oil with steam. It also appears to be possible
io accumulate the compound by treating the fractions in question with
glacial acetic-sulphuric acid at 40° to 50° for several hours. From the
formation of esters, it is clear that the body C 10 H 18 O 2 is an alcohol. Its
acetic ester, of which the odour differs altogether from that of linalyl
acetate, boils between 60° and 65° (4 mm.), and its benzoic ester between
157° and 160° (3 to 4 mm.). These chemists have also isolated the
hydrocarbons octylene^3 (previously found in bergamot oil by Burgess and
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4
) and nonylene from the oil. An oleginic terpene is also present,
possibly identical with myrcene.
Linaloe oil is a colourless or pale yellow oil of sweet, soft odour, that
of linalol predominating. It has the following characters:—
Specific gravity.. 0-875 to 0898
Optical rotation.. - 3° to - 15° (sometimes dextro-rotatory to + 8°)
Refractive index.. 1-4590 to 1-4655
Acid value. 0 ,, 6
Ester „ , ,. 5 „ 75
The oil is soluble in 3 volumes of 70 per cent, alcohol, or in 4 to 5
volumes of 60 per cent, alcohol.
Occasionally pure oils will be found which vary outside these limits.
Thus, oils with a high content of linalol oxide may have a specific gravity
of 0900 or even a little over. Oils with a high ester value naturally
contain less free linalol.
The amount of free linalol is the most important feature of the oil.
Its actual determination is difficult, if not impossible, on account of the
ease with which it decomposes under the action of acetic anhydride.
Boulez's modification of the usual acetylation process, however, yields
approximately correct results.
A fractional distillation is most useful, and will give a good indication
of the amount of linalol present. The following results were obtained on
fractionating four pure samples, by the author and C. T. Bennett:—
(^1) Berichte, October, 1908, 78. (^2) /6id., 42 (1912), 4811.
(^3) Schimmel's Report, April, 1909, 67. 4 Jour. Chem. Soc., 85 (1904), 1327.