Length of the Methylene Bridges in Cellulose Formals Determined by 18O Tagging and by Other Methods

Abstract

Cellulose formals cellulose-O(CH ₂O) _n -cellulose were made by reacting purified cotton yarn with formaldehyde in the presence of H₂ ¹⁸O. Average values for n were determined from the ratio of excess ¹⁸O in the formals to formaldehyde bi- functionally attached to the cellulose. Values of n ranging from 1.3 to 3.2 were obtained, depending on the reaction con ditions. The lower values of n were obtained at the lower formaldehyde concentrations, shorter reaction times, and elevated temperatures. A cellulose formal was made also by reacting cotton with the potassium salt of methylenedisul furic acid in the presence of H ₂ ¹⁸O and NaOH; its average n value was about 1.6. The n values obtained were compared with previously reported values obtained by determining the ratio of weight loss to formaldehyde loss when foremaldehyde was removed by exposure of the formals to moist HCl vapor and also with values obtained by H. Zollinger by permethyl ation, hydrolysis, and gas chromatography.