Se-N interactions in selenohydroxylamine: a theoretical study

The potential energy surfaces of thiohydroxylamine HS-NH2, 1, and selenohyd roxylamine HSe-NH2, 2, have been searched, using ab initio and density func tional methods, to study the conformational preferences. There are two mini ma on the path of rotation around the Se-N bond in 2. High accuracy G2MP2 c alculations showed that the Se-N rotational barrier in 2 is 5.41 kcal mol(- 1), which is 1.16 kcal mol(-1) less than the S-N rotational barrier in 1. T he inversion around N in 1 and 2 goes through low energy barriers of 1.79 a nd 2.44 kcal mol(-1) at the same level respectively. Charge analysis using the natural population analysis (NPA) method has been performed to understa nd the electronic factors responsible for the observed trends in the Se-N i nteractions. The strength of the negative hyperconjugation in 2 has been es timated using natural bond orbital (NBO) analysis and by studying the subst ituent effect.