Studies on the application of the quinhydrone electrode in formamide. VII. The ionization constants and related thermodynamic quantities of (E)-cinnamic acid from E.M F. measurements at different temperatures

Abstract

The e.m.f. of the cell Ag-AgCl/NaCl(m₃), NaA(m₂), HA(m₁) QH₂-Q/Pt (where HA is cinnamic acid) in formamide has been measured at 5º intervals over the temperature range 5-45ºC. The pK_a value of (E)-cinnamic acid ranges from 7.02 ± 0.03 at 5º to 6.78 ± 0.05 at 45º.