Hydride shift in substituted phenyl glyoxals: Interpretation of experimental rate data using electronic structure and variational transition state theory calculations
G. Tresadern et al., Hydride shift in substituted phenyl glyoxals: Interpretation of experimental rate data using electronic structure and variational transition state theory calculations, PHYS CHEM P, 3(18), 2001, pp. 3967-3972
Experimental rate data for hydride transfer in some p-substituted phenyl gl
yoxals in 80 : 20 dioxan : water are presented including kinetic hydrogen i
sotope effects. The roles of different substituents are discussed using ele
ctronic structure calculations of the potential energy surfaces at the SM5.
4/PM3 level together with calculations employing variational transition sta
te theory and multidimensional tunneling. p-NO2 substitution has the most p
ronounced effect on the rate parameters, which can be understood in terms o
f the relative destabilisation of the reactant and reduced quantum mechanic
al tunneling through the barrier. The use of different models for tunneling
suggests that when coupled with the SM5.4/PM3 method, the higher level of
theories tend to overestimate the degree of tunneling.