T 1415 (OTTO) Tetrahydrofuran, 99% Cas 109-99-9 - used as an aprotic solvent with moderate polarity in chemical reaction and solvent. T 1415 (OTTO) Tetrahydrofuran, 99% Cas 109-99-9- used industrial process involves the acid-catalyzed dehydration of 1,4-butanediol.