Heptoyl chloride

Prepare n-heptoyl chloride from the acid by treatment with thionyl chloride as detailed for n-butyryl chloride (Section 111,87) b.p. 173-175°. 

A. Heptoic anhydride enanthic anhydride). In a 250-ml. round-bottomed three-necked flask, equipped with a stirrer, dropping funnel, and thermometer, are placed 15.8 g. (16.1 ml., 0.2 mole) of dry pyridine (Note 1) and 25 ml. of dry benzene (Note 2). I hen 14.8 g. (15.5 ml., 0.1 mole) of heptoyl chloride (Note 3) is added rapidly to the stirred solution. The temperature rises only slightly, and a pyridinium complex separates. While stirring is continued, 13.0 g. (14.1 ml., 0.1 mole) of heptoic acid (Note 3) is added from the dropping funnel over a period of 5 minutes. The temperature rises rapidly to 50-65° (Note 4), and pyridine hydrochloride is formed. After stirring for 10 minutes, the solid is collected on a chilled Buchner funnel and washed twice with 25-ml. portions of dry benzene (Note 5). 

The heptoyl chloride, b.p. 173-175°, and the heptoic acid, b.p. 108-109°/9 mm., were obtained from the Eastman Kodak Company. 

Because of a possible similarity between them and the group of reactions just dealt with, it is convenient to mention here some reactions which have been used to prepare carboxylic acid anhydrides. Minunni observed the formation of benzoic acid anhydride in high yield when benzoylpyridinium chloride was treated with water, and the reaction is generally useful . From the fatty acid series the reaction of heptoyl chloride with pyridine in benzene, followed by the addition of heptoic acid, provides an example of anhydride formation in high yield . More recently, anhydrides were prepared from acid chlorides and aqueous solutions of the corresponding sodium salts containing catalytic amounts of pyridine . It seems possible that... 

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