Rate constant and activation energy determination for reaction of e⁻_(aq) and ^•OH with 2-butanone and propanal

Abstract

The techniques of pulse radiolysis and absorption spectroscopy have been used to determine kinetic parameters for e−(aq) and •OH reaction with 2-butanone and propanal. The temperature dependent rate constants for hydrated electron reaction are given by ln k(T) = (28.96 ± 0.06) − (1970 ± 20)/T' (2-butanone, 275–343 K), and ln k(T) = (29.2 ± 0.2) − (2160 ± 50)/T (propanal, 275–310 K), where the given uncertainties are 1σ and only represent precision, and the rate constants are in units of M−1 s−1. For hydroxyl radical reaction over the same temperature ranges. ln k(T) = 25.32 ± 0.02) − (1460 ± 40)/T (2-butanone) and ln k(T) = (32.73 ± 0.03) − (3310 ± 100)/T (propanal).

Kinetics of reactions of OH with organic carbonyl compounds in aqueous solution

“…Assuming an H-abstraction mechanism it can be said that molecules with a smaller C-H bond dissociation energy are more reactive but the measured rate constants of the aldehydes investigated in this study and elsewhere 19,30,31,44 seem to be independent of the bond dissociation energy for low BDE values (BDE r 374 kJ mol À1 ). The reason for this aldehyde behaviour is still unclear (Fig.…”

“…For the reaction of OH with acetaldehyde, Schuchmann et al 30 have given a set of three rate constants for the reactions of OH with acetaldehyde, its hydrated form and the equilibrium mixture of acetaldehyde and its hydrate. However, the literature gives only rate constants for the reaction of OH with the equilibrium mixtures of propionaldehyde 31,44 and butyraldehyde. 19,31 Therefore, the rate constants for the reaction of OH with the mixtures of aldehydes and their hydrates are considered in the present study (Fig.…”

Temperature-dependent rate constants for hydroxyl radical reactions with organic compounds in aqueous solutions

“…11 that two points significantly deviate from all others. Firstly, the value for propanal available from the literature 38 is about three orders of magnitude higher than the others. Based on the kinetic study by Mezyk 38 the strong deviation cannot be explained.…”

“…Firstly, the value for propanal available from the literature 38 is about three orders of magnitude higher than the others. Based on the kinetic study by Mezyk 38 the strong deviation cannot be explained. Possible influences of hydration effects can be neglected for propanal.…”

Absolute rate constant measurements for the reaction of atomic hydrogen with acetone, 2-butanone, propionaldehyde, and butyraldehyde in aqueous solution

“…In a recent investigation (7), rate constants and activation energies were determined for hydrated electron and hydroxyl radical reaction with these carbonyls, using the techniques of pulsed electron radiolysis and absorption spectroscopy. However, the pulse radiolysis of these compounds in acidic solutions containing tbutanol showed no change in the visible or near-uv absorption 'Work at Argonne performed under the auspices of the Office of Basic Energy Sciences, Division of Chemical Science, US-DOE, under contract W-3 1 -109-ENG-38.…”