Site-specific rate coefficients for reaction of OH with ethanol from 298 to 900 K

Abstract

The rate coefficients for reactions of OH with ethanol and partially deuterated ethanols have been measured by laser flash photolysis/laser-induced fluorescence over the temperature range 298?523 K and 5-100 Torr of helium bath gas. The rate coefficient, k1.1, for reaction of OH with C 2H5OH is given by the expression k1.1 = 1.06×10?22T3.58-exp(1126/T) cm3 molecule?1 s?1, and the values are in good agreement with previous literature. Site-specific rate coefficients were determined from the measured kinetic isotope effects. Over the temperature region 298-523 K abstraction from the hydroxyl site is a minor channel. The reaction is dominated by abstraction of the α hydrogens (92 ± 8)% at 298 K decreasing to (76 ± 9)% with the balance being abstraction at the β position where the errors are 2?. At higher temperatures decomposition of the CH 2CH2OH product from β abstraction complicates the kinetics. From 575 to 650 K, biexponential decays were observed, allowing estimates to be made for k1.1 and the fractional production of CH2CH2OH. Above 650 K, decomposition of the CH 2CH2OH product was fast on the time scale of the measured kinetics and removal of OH corresponds to reaction at the α and OH sites. The kinetics agree (within ±20%) with previous measurements. Evidence suggests that reaction at the OH site is significant at our higher temperatures: 47-53% at 865 K. © 2011 American Chemical Society.