Caproic anhydride

One hundred and sixteen grams (126 cc., 1 mole) of M-caproic acid is placed in a 250-cc. gas-washing bottle. The bottle is supported in an ice bath, and 0.50 to 0.55 mole of ketene is passed into the acid at a rate of approximately 0.45 mole per hour (Notes 1 and 2). 

The resulting mixture is transferred to an apparatus for fractional distillation, and carefully fractionated, an oil bath being used for heating (Note 3). A low-boiling fraction, consisting of acetone containing some ketene, acetic acid, and a small quantity of acetic anhydride, is removed at atmospheric pressure. As the distillation progresses the temperature of the oil bath is raised to 220° over a period of about an hour and held there until three hours have elapsed from the time distillation started (Note 4). 

The distillation at atmospheric pressure is then discontinued, the liquid is allowed to cool somewhat, and distillation is continued at a pressure of 3-10 mm. After a fore-run of less than 20 g., M-caproic anhydride is collected (b.p. io9-xi2°/3 mm., n8-i2i°/6 mm.). The yield is 86-95 g. (80-87 Per cent °f the theoretical amount) (Note 5). 

Ketene may be generated conveniently, at the proper rate, in the apparatus described by Williams and Hurd.1 

Addition of one mole of ketene per mole of acid does not increase the yield. Under these conditions more acetic anhydride is found in the low-boiling fraction. 

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The best results are obtained with a fractionating column surrounded by an electrically-heated jacket (compare Figs. II, 17. 2. and II. 17, 3), but this is not essential for n-caproic anhydride. For the preparation of propionic or n-biityric anhydride, a highly efficient fiactionating column must be used in order to obtain satisfactory results. 

In a modification of this scheme, hydroxypregnenolone is first acetylated under mild conditions to the 3-acetate and then under forcing conditions with caproic anhydride to give the acetate-caproate (122). Ester interchange with methanol removes the acetate at 3 Oppenauer oxidation affords hydroxyprogesterone caproate (124). ... 

Cadaverine, p30 2-Camphanone, c3 Capraldehyde, d7 Capric acid, dl5 Capric alcohol, dl6 Caproaldehyde, h51 Caproic acid, h64 Caproic anhydride, h65 6-(or e)-Caprolactam, 06I e-Caprolactone, h69... 

To resolve any uncertainty caused by the difference between acetate and caproate in the active substrate an experiment was attempted using caproic anhydride as the substrate. The reaction could not be followed, however, presumably because of the low solubility of caproic anhydride. 

Submitters and checkers used a column of the Whitmore-Lux type,2 12 mm. in diameter, 50 cm. long, packed with glass helices (Org. Syn. 20, 96, Note 8), and provided with the usual jackets for heating. A less efficient column will serve in the preparation of caproic anhydride but not in the preparation of propionic anhydride or butyric anhydride by the same method. 

It is imperative to continue the distillation at atmospheric pressure until conversion of any mixed anhydride to caproic anhydride is complete. The acetic acid formed by this conversion comes off very slowly, and approximately three hours are necessary to complete the distillation at atmospheric pressure. 

M-Caproic anhydride has been prepared by heating caproic acid with acetic anhydride,3 by heating sodium caproate and acetic anhydride in a sealed tube,4 by the action of phosphorus oxychloride on barium caproate,6 by the action of acetyl chloride on caproic acid,6 and by treating a mixture of sodium caproate and sulfur with chlorine.7 The method used in the present synthesis was first described by Hurd and Dull.8... 

Capric acid, dl4 Caproaldehyde, h54 Caproic acid, h66 Caproic anhydride, h67 e-Caprolactam, o57 6-Caprolactone, h71 Capronitrile, h63 Caproyl chloride, h73 Caprylic acid, o29 Capryl alcohol, o30 Caprylaldehyde, o40... 

M-CAPROIC ANHYDRIDE, 21, 13 Capronitrile, 26, 33 Caproylchlororesorcinol, 20, 58 o-Caproylphenol, 20, 58 -Caproylphenol, 20, 58 Caproylresorcinol, 20, 58 w-Carbethoxypelargonyl chloride, 25, 21 5-Carbethoxyvaleiyl chloride, 25, 21 CARBINOL, TRIPHENYL-, 23, 98 Carbinol, tris-(4-phenylphenyl)-,... 

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