THE LOCATION OF XANTHATE GROUPS IN PARTIALLY SUBSTITUTED STARCH XANTHATES

Abstract

The rate of xanthation of starch with carbon disulphide in 17.8% potassium hydroxide at 23° was followed by converting the potassium salts to the S-methyl xanthate esters, and analyzing the latter for sulphur. These esters were tritylated without changing the xanthate D.S., and unity minus the trityl D.S. was assumed to represent xanthate D.S. in the primary alcohol positions of the starch. About 62% of the xanthate groups occupied secondary positions after 100 minutes of xanthation, but after 3350 minutes about 58% of the surviving xanthate groups were primary.A sodium chlorite–pyridine–lactic acid mixture reduced the sulphur content of a fully acetylated starch S-methyl xanthate by about nine-tenths with little loss of acetyl groups, but the residual sulphur could not be eliminated and the resulting starch acetate could not be completely reacetylated or tosylated. The location of the hydroxyl groups in this acetate thus could not be studied by the tosylation–iodination method.