Aldehyde-Bisulfite Adducts: Prediction of Some of Their Thermodynamic and Kinetic Properties

Stability constants (K₁) for the reaction of acetaldehyde and hydroxyacetaldehyde with NaHSO₃, determined spectrophotometrically in aqueous solution, were found to be (6.90 ± 0.54) × 10⁵ M^-1 (2.0 ± 0.5) × 10⁶ M^-1 respectively, where K₁ (corrected for aldehyde hydration) = [RCH(OH)SO₃^-]/[RCHO][HSO₃^-] (μ = 0.2 M; 25 °C). Acid dissociation constants (pK_a3) of a series of α-hydroxyalkanesulfonate salts, RCH(OH)SO^-₃, were found to be 11.46 (CH₃-), 11.28 (H-), 10.30 (HOCH₂-), 10.33 (C₆-H₅-), 10.31 (CH₃CO-), and 7.21 (Cl₃C-) (μ = 0 M; 25 °C). Simple straight-line relationships were found to exist between Taft's σ* parameter and a number of thermodynamic and kinetic properties of some aldehydes. K₁ K_a3, and the rate constant for nucleophilic addition of SO^2-₃ all increase linearly with σ*. Carbonyl species such as halogenated derivatives of acetaldehyde, certain β- and γ-dicarbonyl aldehydes, and perhaps also some highly (halogen) substituted ketones, i.e., all those species with ∑σ* ≥ ~1.5 (aldehydes) or ∑σ* ≥ ~2.5 (ketones), could be important S(IV) reservoirs.