Aldehyde-bisulfite adducts: prediction of some of their thermodynamic and kinetic properties

Abstract

Stability constants (K_1) for the reaction of acetaldehyde and hydroxyacetaldehyde with NaHSO_3, determined spectrophotometrically in aqueous solution, were found to be (6.90 ± 0.54) x 10^5 M^(-1) and (2.0 ± 0.5) x 10^6 M^(-1) respectively, where K_1 (corrected for aldehyde hydration) = [RCH(OH)SO_3^-]/[RCHO][HSO_3^-] (µ = 1 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 (CH_3-), 11.28 (H-)10.30(HOCH_2-),10.33 (C_(6-)H_5-),10.31 (CH_3CO-), and 7.21 (Cl_3C-)(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. K_1, K_(a3), and the rate constant for nucleophilic addition of SO_3^(2-) 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, ie., all those species with ∑σ* ≥ ~1.5 (aldehydes) or ∑σ* ≥ ~2.5 (ketones), could be important S(IV) reservoirs.

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