CATALYTIC THERMOMETRIC TITRATIONS OF VARIOUS MIXTURES OF NITROGEN BASES

The reactions of acetylation of hydroquinone and quinhydrone with acet ic anhydride, catalysed by perchloric acid, were used to determine the end point of catalytic thermometric titrations of a number of differe nt amines and amides dissolved either in acetic anhydride or in acetic acid-acetic anhydride (10+1) mixture. In the majority of cases primar y and secondary amines could be successfully determined if pK(b)less t han or equal to 9.3, tertiary amines if pK(b)less than or equal to 14, and amides if pK(b)less than or equal to 15. Thanks to the difference in behaviour of organic bases in acetylation reaction, it was possibl e in some instances to determine selectively the individual bases in t heir mixtures. Catalytic titrations appeared to be especially suitable for the determination of extremely weak bases, even in the case of us ing mixtures of organic solvents, when potentiometric titrations could not be employed. Amounts of 2.5 10(-6)-8.10(-5) mole of bases were de termined with a maximal relative standard deviation less then 2%.