Org. Synth. 1926, 6, 68
DOI: 10.15227/orgsyn.006.0068
d- and l-OCTANOL-2
[2-Octanol, d- and l-]
Submitted by Joseph Kenyon
Checked by Roger Adams and F. E. Kendall.
1. Procedure
(
A)
Preparation of sec.-Octyl Hydrogen Phthalate.—A mixture of
130 g. (1 mole) of sec.-octyl alcohol (p. 366) and
148 g. (1 mole) of phthalic anhydride is heated for twelve to fifteen hours in a
flask surrounded by an
oil bath at 110–115°
(Note 1). During the heating the mixture should be mechanically stirred or shaken occasionally to give a homogeneous liquid. The cooled reaction mixture is added to about 8 l. of water which contains
150 g. (1.4 moles) of anhydrous sodium carbonate. The solid material gradually goes into solution, and if the resulting solution is perfectly clear, dilute
hydrochloric acid is added in slight excess, thus precipitating the
sec.-octyl hydrogen phthalate as an oil which rapidly turns to a solid; if the alkaline solution is not clear, owing to the presence of
methyl hexyl ketone in the original alcohol, it should be extracted with
ether to remove the ketone before acidifying with
hydrochloric acid.
The octyl hydrogen phthalate is filtered, washed with water, ground thoroughly with water in a mortar, and finally filtered and dried. For complete purification it may be crystallized either from petroleum ether (b.p. 60–70°) or glacial acetic acid, from which it separates as needles melting at 55°. The crude material, however, is perfectly satisfactory for the following experiments. The yield is nearly quantitative if the sec.-octyl alcohol is pure (Note 2) and (Note 3).
(B) Resolution.—A warm solution of 278 g. (1 mole) of sec.-octyl hydrogen phthalate and 600 cc. of acetone is treated with 394 g. (1 mole) of brucine and the mixture warmed until the solution is clear. Upon cooling, the crystals of brucine salt (A) form. These are filtered, pressed, and washed in the funnel with 250 cc. of acetone. The combined filtrate and washings are concentrated to about 50 per cent of their original volume and then poured into dilute hydrochloric acid (slightly more than the calculated amount), which causes the precipitation of the sec.-octyl hydrogen phthalate. After the precipitate sets to a crystalline mass, it is filtered, washed with cold water, and dried. This weighs approximately one-half of the original ester used and has a rotation [α]5461 − 47° in absolute alcohol solution (Note 4).
The crystals (A) are dissolved in the minimum amount of hot ethyl alcohol and decomposed by pouring the solution into dilute hydrochloric acid. The weight of the ester thus obtained is about one-half of that originally taken, and its rotation in absolute alcohol is about [α]5461 +47°, [α]D +44°.
The two lots of crude active sec.-octyl hydrogen phthalate are now separately crystallized twice from acetic acid (about 2 g. of 90 per cent acetic acid should be used for each gram of solid). They are thus obtained in an optically pure condition and possess the rotations [α]5461 − 58.5°, [α]D − 48.4° and [α]5461 +58.3°, [α]D +48.4°, respectively. The amount of pure product, m.p. 75°, obtained in each case is respectively about 99 g. and 96 g. (about 70 per cent of the theoretical amount). The sec.-octyl hydrogen phthalate of low optical activity obtained by adding water to the acetic acid filtrates can be collected and used in a subsequent preparation.
(C) Hydrolysis.—Optically pure l- and d-sec.-octyl alcohols are obtained by distillation in a current of steam of the sec.-octyl hydrogen phthalate and 2 moles of sodium hydroxide in 30 per cent solution. The alcohols are practically insoluble in water and are separated, dried with potassium carbonate, and distilled. Each boils at 86°/20 mm. and has a rotation [α]17°5461 + 11.8°, [α]17°D + 9.9° or [α]17°5461 − 11.8°, [α]17°D − 9.9°. The yields of alcohol from the sec.-octyl hydrogen phthalates are about 95 per cent of the calculated amounts.
2. Notes
1.
If this temperature is exceeded the yield of
octyl phthalate is reduced and the color of the product is very dark. The color is carried through with the
l-fraction, making it difficult to read rotations.
2.
The yield of
sec.-octyl hydrogen phthalate from the crude
sec.-octyl alcohol used in this preparation was
61–64 per cent.
3.
It is reported that
sec.-octyl hydrogen phthalate may be prepared in a purer state and with better yields if the reaction is carried out in the presence of
pyridine according to the procedure of Levene and Mikeska for preparing the
acid phthalate of
cyclohexyl phenyl carbinol1 (H. L. Haller, private communication).
4.
Frequently this product is so dark that a determination of rotation is impossible.
3. Discussion
The resolution of
sec.-octyl alcohol was first described by Pickard and Kenyon.
2 The method employed by these authors differs from the procedure described in the following respects. The
brucine salt of sec.-octyl hydrogen phthalate was crystallized several times from
acetone until it reached optical purity and was then decomposed to give pure
d-sec.-octyl hydrogen phthalate. The partly levorotatory
hydrogen phthalic ester obtained by the decomposition of the more soluble fractions of the
brucine salt was then combined with
cinchonidine and the
cinchonidine salt crystallized some half-dozen times from
acetone until optical purity was reached. Decomposition of this salt yielded the optically pure
l-sec.-octyl hydrogen phthalate.
The procedure described
3 is much more convenient.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
petroleum ether
ester
brucine salt
acid phthalate
hydrogen phthalic ester
cinchonidine salt
D- and L-Octanol-2
2-Octanol, d- and l-
d-sec.-octyl alcohols
sec.-octyl hydrogen phthalates
brucine salt of sec.-octyl hydrogen phthalate
ethyl alcohol,
alcohol (64-17-5)
potassium carbonate (584-08-7)
hydrochloric acid (7647-01-0)
acetic acid (64-19-7)
ether (60-29-7)
sodium hydroxide (1310-73-2)
sodium carbonate (497-19-8)
phthalic anhydride (85-44-9)
acetone (67-64-1)
pyridine (110-86-1)
sec.-octyl alcohol (123-96-6)
sec.-Octyl Hydrogen Phthalate,
d-sec.-octyl hydrogen phthalate,
l-sec.-octyl hydrogen phthalate (5393-19-1)
methyl hexyl ketone (111-13-7)
octyl hydrogen phthalate,
octyl phthalate
brucine
cyclohexyl phenyl carbinol
cinchonidine (485-71-2)
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