3652-86-6Relevant articles and documents
Experimental and theoretical multiple kinetic isotope effects for an SN2 reaction. An attempt to determine transition-state structure and the ability of theoretical methods to predict experimental kinetic isotope effects
Fang, Yao-ren,Gao, Ying,Ryberg, Per,Eriksson, Jonas,Kolodziejska-Huben, Magdalena,Dybala-Defratyka, Agnieszka,Madhavan,Danielsson, Rolf,Paneth, Piotr,Matsson, Olle,Westaway, Kenneth Charles
, p. 2696 - 2709 (2007/10/03)
The secondary α-deuterium, the secondary β-deuterium, the chlorine leaving-group, the nucleophile secondary nitrogen, the nucleophile 12C/13C carbon, and the 11C/14C α-carbon kinetic isotope effects (KIEs) and activation parameters have been measured for the SN2 reaction between tetrabutylammonium cyanide and ethyl chloride in DMSO at 30°C. Then, thirty-nine readily available different theoretical methods, both including and excluding solvent, were used to calculate the structure of the transition state, the activation energy, and the kinetic isotope effects for the reaction. A comparison of the experimental and theoretical results by using semiempirical, ab initio, and density functional theory methods has shown that the density functional methods are most successful in calculating the experimental isotope effects. With two exceptions, including solvent in the calculation does not improve the fit with the experimental KIEs. Finally, none of the transition states and force constants obtained from the theoretical methods was able to predict all six of the KIEs found by experiment. Moreover, none of the calculated transition structures, which are all early and loose, agree with the late (product-like) transition-state structure suggested by interpreting the experimental KIEs.
