Acidity of HOCN, HSCN, HNCO, HNCS: A treatment from the viewpoint of ab initio approach

Alexei Pankratov, Sergei Khmelev
2005 Journal of the Serbian Chemical Society  
The electronic structures of the molecules HOCN, HSCN, HNCO, HNCS and the anions [OCN] -, [SCN]have been investigated ab initio at the RHF/6-31G(d), RHF/6-31G(d,p), MP2/6-31G(d)//RHF/6-31G(d) and MP2/6-31G(d,p)//RHF/6-31G(d,p) theory levels. The thermodynamic stability of the HNCO and HNCS molecules was shown to be higher than that of the HOCH and HSCN molecules, respectively.The following series of the alteration of the protolytes strength HSCN > HOCH, HNCS > HNCO, HOCN > HNCO, HSCN > HNCS was
more » ... CO, HSCN > HNCS was substantiated. The computations taking into account the electronic correlation (MP2/6-31G(d)//RHF/6-31G(d) and MP2/6-31G(d,p)//RHF/6-31G(d,p)) reflect the general sequence of change in the proton-donor properties: HSCN > HOCN > HNCS > HNCO, coinciding with the order of descending hydrophobicity of the compounds. The comparative proton-donor ability of the above acids in aqueous solutions is determined basically from the electronic structure and size of their molecules and anions [OCN] -, [SCN] -, but not on medium effects.
doi:10.2298/jsc0510183p fatcat:5oi5dvx2fnfg5iubtxbq6a6au4