The equilibrium constants for bisulfite addition to acetophenone, 2-choloroacetophenone and trans-cinnamaldehyde were determined using an ultraviolet spectrophotometric method. The absorbance of the carbonyl compound was monitored as aliquots of a bisulfite solution were added to the reaction cell. By plotting 1/A versus [HSO3-], and dividing the slope by the intercept, it was possible to determine Keq. All determinations were made at pH 4.66 and ionic strength 1.0. By determining Keq at various temperatures it was also possible to determine ΔH° and ΔS°. The equilibrium constants for bisulfite addition to: acetophenone, 2-choloracetophenone and trans-cinnamaldehyde, were determined to be: 5.8 M-1, 53 M-1, and 1030 M-1 respectively. The rate constants for bisulfite addition to trans-cinnamaldehyde were also determined using an ultraviolet spectrophotometric method. The change in absorbance, after the addition of bisulfite, was monitored at one second intervals for fifteen minutes. The forward and reverse rate constants for bisulfite addition to trans-cinnamaldehyde were determined to be, 24.3 M-1 s-1 and 2.4x10-2 s-1 respectively
