Non-aqueous quantitative determination of the carbonyl functional group by constant-current potentiometric titration

Abstract

A non-aqueous direct titration procedure has been developed for the determination of aldehydes and ketones. It uses two platinum-wire indicating electrodes with a constant current of 0̃.5 μA. The solvent medium is 0.15 M sodium perchlorate in tetrahydrofuran. The titrant is sodium fluorenyl in a mixture of 1,2-dimethoxyethane and tetrahydrofuran. All types of carbonyl compounds react with the sodium fluorenyl, but steric hindrance prevents complete reaction with certain ketones containing bulky groups. The lowest concentration of carbonyl that can be determined with acceptable accuracy and precision is 7.5 × 10 −3 M, the error being < 3% and the precision better than ±2.5%. Most reducible compounds interfere, e.g., peroxides, acid halides, nitro-compounds, acids, and water, and cannot be differentiated potentiometrically. The method can be extended to other reducible functional groups, e.g., nitro groups and acid chlorides.