Secondary hydrogen isotope effects. Part 5. Acid and base strengths: corrigendum and addendum
Abstract
The effect of deuteriation of the methylene group on the acid strength of phenylacetic acid and the base strength of benzylamine are reinvestigated, using both the differential potentiometric method described in Part 1 of this series and a newly developed differential n.m.r. method, which is described. The differential potentiometric method is established to be sound, but the ΔpKa values reported earlier could not be reproduced and are withdrawn in favour of the following values, obtained by the old method and confirmed by the new: PhCD2CO2H–PhCH2CO2H, ΔpKa( pKaD– pKaH)= 0.005 ± 0.003; PhCD2NH3+–PhCH2NH3+, ΔpKa= 0.032 ± 0.001.