Tautomeric properties, conformations and structure of 2-hydroxyacetophenone methanesulfonylhydrazone

The compound, 2-hydroxyacetophenone methanesulfonylhydrazone (apmsh) has been synthesized and its crystal structure has been investigated by X-ray analysis. The compound crystallizes in the monoclinic space group P21/c and the following unit cell parameters: a = 20.9496(15) Å, b = 4.9849(4) Å, c = 10.2300(8) Å; α = 90°, β = 98.2750(10)°, γ = 90°; V = 1057.21(14) ų and Z = 1. The molecular geometry of the apmsh in the ground state has been calculated using the restricted Hartree-Fock with HF/6-31G** and density functional method with B3LYP/6-31G** basis set. The optimized bond lengths and bond angles obtained by using B3LYP/6-31G** are in better agreement with the experimental values than those by using RHF/6-31G**. The conformers located at minima by PM3 semi-empirical calculation were re-optimized by using B3LYP/6-31G** method. Quantum-chemical calculations indicate that enol-imine tautomeric form is favored and the most stable conformer in gas phase is approximately 6 kcal/mol stable than next conformer.