Henry's law constants of some environmentally important aldehydes

Abstract

The Henry's law constants of seven aldehydes have been determined as a function of temperature by bubble-column and by head-space techniques. The compounds were chosen for their potential importance in the polluted troposphere and to allow structure-reactivity patterns to be investigated. The results (at 25 ºC) are as follows (in units of M atm^(-1)): chloral, 3.44 X 10^5; glyoxal, ≥ 13 X 10^5; methylglyoxal, 3.71 X 10^3; formaldehyde, 2.97 X 10^3; benzaldehyde, 3.74 X 10^1; hydroxyacetaldehyde, 4.14 X 10^4; acetaldehyde, 1.14 X 10^1. A plot of Taft's parameter, ∑σ^*, vs log H^* (the apparent Henry's law constant) gives a straight line with a slope of 1.72. H^* for formaldehyde is anomalously high, as expected, but the extremely high value for hydroxyacetaldehyde was unexpected and may indicate that α-hydroxy-substituted aldehydes could have an unusually high affinity for the aqueous phase. The intrinsic Henry's law constants, H, corrected for hydration, do not show a clear structure-reactivity pattern for this series of aldehydes.

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