Titrations of some steroidal bases in non-aqueous media

Abstract

The potentiometric and catalytic thermometric titrations of some newly synthetised steroidal compounds containing the pyridine nucleus are performed with 0. 1 M perchloric acid in acetic acid. Amounts of 15.32-37.71 mg were determined with a relative standard deviation < 0.89 %. Results of separate determinations of the bases by catalytic thermometric and potentiometric titration are in good agreement. By means of the data of potentiometric titrations, pK-values of the investigated compounds were estimated and some possible explanations are provided for the noticeable differences in the two pairs of geometrical isomers. The obtained results show that these compounds behave as relatively stronger bases (pK 6.04-7.03) in acetic acid. It has also been found that the introduction of one vinyl-group into α-position of the pyridine nucleus has no essential influence on the basicity, as confirmed by the obtained pK-values. Determination of the isomeric ketones, 3 β-acetoxy-17-picolinylidene-5-androstene-16-ones, in mixture was successfully performed by potentiometric titration in acetic anhydride only. © 1982 Springer-Verlag.