A.R. Samzadeh, H. Tavakol, Theoretical study of inter and intramolecular proton transfer in N-hydroxy amidines, Fourth International Symposium in Methods and Applications of Computational Chemistry, June 2011, Lviv, Ukraine

Abstract

N-hydroxy amidine [1] is an important and useful group in synthesis of various compounds[2] in organic chemistry and some other applications can be considered for this group [3].

This functional group is found in two tautomeric forms; one is amino-oxime (tautomer a) and the other is imino-hydroxylamine (tautomer b). In our study, at first, we optimized the structure of each tautomer and after that; IR frequencies, energies and other molecular parameters of tautomers have been computed by quantum mechanic calculations, using Gaussian 03 with 6-311++G** basis set in both ab initio and density functional methods with basis set extrapolation and MP2 correction of energy. The result found in both methods shows that the tautomer a is more stable than the tautomer b.

In next step, we guessed the structure of transition state for each pair of tautomers and optimized by QST3 calculations. The strusture of shered part of all transition states showed in below. After all, we computed the energy and molecular parameters of transition states. Our finding shows that, the energy difference between two tautomers is low but the barrier energy found in traversing of each tautomer to another one is high.