Phthalic anhydride 3-PHTHALYL CHLORIDE, SYMMETRICAL

Phosphorus, 13, 60 Phosphorus oxychloride, 12, 66 Phosphorus pentachlorlde, 12, 12 Phosphorus tribromide, 13, 20 Phosphorus trichloride, 12, 16 Phosphorus trisulfidc, 12, 72, 73 Phthalic anhydride, 11, 88 13, 10 Phthalide syntheas, 13, 10 Phthalimide, 12, 10 Phthalimide synthesis, 12, 10 p-Phthalyl chloride, symmetrical,... 

Symmetrical o-phthalyl chloride has been prepared by heating phthalic anhydride and phosphorus pentachloride in sealed tubes.1 This method is not convenient for the preparation of large quantities. 

It will be recalled that in the case of succinyl chloride both of these forms are obtained, but mostly the symmetrical (p. 282). Now from phthalic anhydride only one phthalyl chloride is obtained. This chloride acts like the unsymmetrical succinyl chloride, not like the symmetrical. The positive proof, however, that phthalyl chloride is the unsymmetrical compound is the following Sodium amalgam reduces phthalyl chloride by replacement of the chlorine with hydrogen. The compound formed is known as phthalide. This phthalide takes up water as anhydrides do and the product is hydroxy-methyl benzoic acid. 

A. Symmetrical o-Phthalyl Chloride A mixture of 148 g. (i mole) of phthalic anhydride (Note i) and 220 g. (r.o6 moles) of phosphorus pentachloride (Note 2) is placed in a 500-cc. Claisen flask. The flask is equipped with a reflux condenser, the upper end of which is provided with a calcium chloride tube, and the side-arm of the flask is closed with a cork. The flask is inclined slightly so that any phosphorus oxychloride which collects in the stoppered side-arm will run back into the flask. After heating in an oil bath at 150° for twelve hours, the air condenser and the stopper in the end of the side-arm are removed, and the flask is connected to a water-cooled condenser. I hc temperature is then raised gradually to 250 , during which... 

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