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Organic syntheses - Roger A.

Roger A. Organic syntheses - Chapman, 1936. - 110 p.
Download (direct link): organicsintencis1936.pdf
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Alcohol is added in portions of about 100 cc. until the emulsion is
broken and the layers begin to separate quite rapidly; usually two or
three additions of alcohol suffice. The lower layer is drawn off and set
aside (Note 8). The oil is washed three times with warm water; if
necessary, alcohol is added to break the emulsion. The ester is dried
with anhydrous calcium chloride, filtered, and distilled under reduced
pressure. The yield of ethyl tridecylate, b.p. i63-i65/5 mm. (i78-
i8o/2o mm.; i97-i98/6o mm.) is 615-660 g. (73-78 per cent of the
theoretical amount). By refractionating the fore- and after-runs, an
additional 50-70 g. of product is obtained; 15-30 g. of ester and acid
are recovered from the ammoniacal washings and from the calcium chloride
used to dry the main portion. The total yield
ETHYL e-TRIDECYLATE
37
is 685-710 g. (81-84 per cent of the theoretical amount) (Notes 9 and
10).
2. Notes
1. A mercury-sealed stirrer may be used, but a " vaseline seal "
is very satisfactory.
2. Potassium cyanide gives better results than sodium cyanide. It
is essential that the material be finely powdered.
3. The entire operation should be carried out in a hood. A small
wash tub placed on the bench and heated from the side with a Bunsen
burner is a convenient water bath.
4. This corresponds to 3.85 moles of potassium hydroxide plus a
quantity sufficient so that, after the hydrolysis is completed, the
solution will contain 10 per cent of alkali. When less than that amount
is used the quantity of unhydrolyzed nitrile is greater.
5. The condenser should' lead to a 2-1. suction flask the side
arm of which is connected directly to the vent of the hood. The alcohol
has the odor of hydrocyanic acid and should be discarded.
6. The crude acid may be used for some purposes, but it contains
a small quantity of unhydrolyzed nitrile, some material of very
disagreeable odor (possibly isocyanide), and usually a small amount of a
blue precipitate (an iron-cyanide complex salt). In the preparation of
the ester, the precipitate is removed by filtering the alcohol solution
of the acid as its presence will interfere with the removal of the free
tridecylic acid after esterification.
7. A few pieces of porous plate should be added to prevent
bumping.
8. By addition of acid to the washings a small amount (15-30 g.)
of ester and acid may be recovered.
9. For larger runs, the procedure is the same and the yields are
somewhat higher. Thus, in runs by the author using twice the above
quantities, yields of 88-89 Per cent were obtained.
10. Pentadecylic acid and ethyl pentadecylate have been prepared
by the same procedure from w-tetradecyl bromide (Org. Syn. 15, 26) with
approximately the same yield.
38
ORGANIC SYNTHESES
3. Methods of Preparation
Tridecylic acid has been prepared by the malonic ester synthesis from
imdecyl iodide,1 by the oxidation of a-hydroxymyristic acid in acetone
with potassium permanganate,2 by the action of dodecyl bromide on
potassium cyanide and subsequent hydrolysis,3 and from undecyl iodide and
ethyl cyanoacetate.4 The present method is an adaptation of that of
Ruzicka, Stoll, and Schinz.3
1 Levene, West, Allen, and van der Scheer, J. Biol. Chem. 23, 73
(1915).
2 Levene and West, ibid. 18, 465 (1914).
3 Ruzicka, Stoll, and Schinz, Helv. Chim. Acta 11, 685 (1928).
'Robinson, J. Chem. Soc. 125, 230 (1924).
XIII
e-HEPTOIC AN? (Enanthic Acid)
3C6Hi3CHO + aKMn04 + H2SO4 ->
3C6H13CO2H + K2SO4 + 2Mn02 + H20
Submitted by John R. Ruhoef.
Checked by C. R. Noller and M. Patt.
1. Procedure
In a 5-I. flask fitted with a mechanical stirrer and cooled in an ice
bath are placed 2.71. of water and 350 cc. (644 g.) of concentrated
sulfuric acid (sp. gr. 1.84). When the temperature has fallen to 15, 342
g. (403 cc., 3 moles) of heptaldehyde (Note 1) is added, followed by 340
g. (2.15 moles) of potassium permanganate in 15-g. portions. The
permanganate is added at such a rate that the temperature does not rise
above 20 (Note 2). When the addition of the permanganate is complete,
sulfur dioxide is passed through the solution until it becomes clear
(Note 3). The oily layer is separated, washed once with water, and
distilled from a modified Claisen flask having a 30-cm. fractionating
side arm. The fore-runs are separated from any water and distilled again;
this is followed by a redistillation of the high-boiling fractions. The
yield of material boiling at 159-i6i/ioo mm. is 296-305 g. (76-78 per
cent of the theoretical amount) (Note 4). This product is sufficiently
pure for many purposes; titration indicates a purity of 95-97 per cent.
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