Stearolic acids

Submitted by Homer Adkins and R. E. Burks, Jr. Checked by Arthur C. Cope and Harold R. Nace. 

Bromine is added dropwise with stirring to 35 g. (0.118 mole) of methyl oleate (Note 1) in a 500-ml. round-bottomed flask. The mixture is kept below 50° throughout the addition, which is continued until a slight excess of bromine is present approximately the theoretical amount (18.9 g.) is decolorized. Methyl oleate (2 or 3 drops) is then added until the bromine color just disappears. w-Amyl alcohol (50 ml.) (Note 2) and potassium hydroxide pellets (40 g., 0.61 mole assuming 85% purity) are added to the flask, and the mixture is heated under reflux for 4 hours in an oil bath at 150°. Then approximately 50 ml. of the w-amyl alcohol is distilled at atmospheric pressure (Note 3). The residue on cooling solidifies into a tan-colored mass. Phe- 

The methyl oleate was prepared by esterification1 of commercial u.s.p. grade oleic acid and fractionated through a Widmer column. The fractions used boiled at 140-144° (0.5 mm.), 175-179° (2 mm.), and had d 1.4500-1.4527 and an iodine number of 93-97 (calcd. 85.6) by iodine bromide titration.2 

-Amyl alcohol was selected as a solvent with a convenient boiling point for the dehydrohalogenation. Acetylenic triple bonds are attacked by water in the presence of strong alkali or strong acid. 

Part of the dehydrohalogenation occurs during the distillation of w-amyl alcohol at atmospheric pressure. If the solution was concentrated by distillation under reduced pressure, the product contained bromine and failed to crystallize. 

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Stearolic acid, C H- Oa, yields stearic acid on catalytic hydrogenation and undergoes oxidative cleavage with ozone to yield nonanoic acid and nonanedioic acid. What is the structure of stearolic acid ... 

How would you synthesize stearolic acid (Problem 27.19) from 1-decyne and l-chIoro-7-iodoheptane ... 

The crude acid is dissolved in 500 ml. of petroleum ether at room temperature. The small amount of amorphous solid which may separate is removed by filtration through Supercel, and the filtrate is concentrated under reduced pressure to 300 ml. Chilling to 0-5° yields a first crop of tan crystals which is collected by suction filtration and washed with the minimum amount of ice-cold petroleum ether. Concentration of the mother liquors to 150 ml. and chilling yields a second crop of brownish crystals. The combined crops are dissolved in 300 ml. of petroleum ether, and the light-red solution is chilled to 0-5°. The almost white to light-tan crystals are collected, washed with a small amount of cold petroleum ether, and dried in a vacuum desiccator. There is obtained 51.5—61.5 g. (51-61%) of stearolic acid, m.p. 46-46.5° (Note 5). 

Sodium >-toluenesulfinate dihydrate, 34, 93 Sommelet reaction, 33, 93 Sorbic acid, 5-hydroxy-0-methyl, 5-lactone, 32, 57 Stannic chloride, 33, 91 Stearic acid, 34, 15 Stearolic acid, 37, 77 Stearone, 33, 84 cis-Stilbene, 33, 88 Irans-Stilbene, 33, 89... 

The liquid stearolic acid is highly susceptible to autoxidation in the presence of air,7 and this portion of the work-up should be conducted in a nitrogen atmosphere. 

This stearolic acid has been thoroughly characterized 3 6 by the freezing-point curve, ultraviolet and infrared spectra, ozonization, and hydrogenation. It has been shown to be free both of positional isomers and of olefinic acids such as oleic and elaidic acids. Its properties include m.p. 46-46.5°, iodine number (Wijs titration, 30 minutes) 89.5, d 5 1.4510, d 5 1.4484, neutral equivalent 279.2-279.6 (theory 280.4), hydrogen uptake 95-100% of theory for a triple bond. The last trace of color is difficult to remove by recrystallization from petroleum ether. It can be removed, however, by crystallization from a 20-30% solution in acetone at —5 to —8°, or from an 8-10% solution at —20°, or by distillation (b.p. 189-190°/2mm.). 

Nearly all methods for preparation of stearolic acid involve de-hydrohalogenation of a 9,10-dihalostearic acid, or its esters, with alcoholic potassium hydroxide the most recent method is that of Adkins and Burks.8 These methods employ drastic conditions, which result in poorer yields than those obtainable on dehydrohalogenation with sodamide.6 Methyl 9,10-dibromostearate, on dehydrobromi-nation with sodamide, yields stearolamide 6 (m.p. 82-83°) which may be hydrolyzed to stearolic acid. For preparative purposes, however, this method offers-no special advantage over that described here. 

Reversing the order of addition, or using an ether as a solvent, causes a marked retardation of the reaction, with subsequent sudden, uncontrollable speed-up. Yields of about 80% are obtained and probably can be improved by devices to minimize the mechanical losses. 0 The addition of hydrogen fluoride to stearolic acid in methylene chloride solution to give 9,10-difluorostearic acid is cited in the patent literature.46 This claim should be verified, as either 9,9- or 10,10-difluoro-stearic acid or a mixture is much more likely to be the reaction product. 

Stearolic acid has been prepared by the dehydrohalogenation of brominated olive or almond oil,3 dibromostearic acid,4 or dichlorostearic acid.6 The procedure described is a modification of one used by Kino.4... 

A triple bond, in stearolic acid, remote from the end group, gives such an increase in attraction for the water, combined with little increase in the lateral adhesion between the chains, that the films are vapour-expanded. This triple bond produces a considerable increase of surface potential. 

Stearolic acid Nonanoic acid Nonanedioic acid... 

Stearolic acid contains a triple bond because the products of ozonolysis are carboxylic acids. 

Stearolic acid better leaving group than chloride. 

Cii 6-Hendecynoic acid Cu a-Naphthylpcopiolic acid C IB Stearolic acid... 

A variety of functionalized acetylenes have been obtained by dehydrohalogenation with NaNHz in liquid ammonia with the functions remaining intact, as illustrated in several examples (equations 54-56). Stearolic acid and 2-butyn-l-ol were obtained... 

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