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Biuret and its sulfur analogs: Structures and energies
Author(s) -
LeszczyńSki Jerzy,
Sullivan Richard H.
Publication year - 1992
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560440216
Subject(s) - conformational isomerism , chemistry , ab initio , dipole , computational chemistry , biuret test , gaussian orbital , molecular geometry , sulfur , ab initio quantum chemistry methods , crystallography , molecule , organic chemistry , urea
The calculations for biuret (B) and its two sulfur analogs, thiobiuret (TB) and dithiobiuret (DTB), were carried out using the ab initio LCAO–MO method at the Hartree–Fock level. The molecular structure of B was fully optimized using standard 3‐21G and 6‐31G* basis sets, while geometry optimizations of the TB's and DTB's were performed at the 3‐21G* and 6‐31G* levels. Only trans ‐isomers were found to be minimum structures on the HF /3‐21G* potential‐energy surfaces, whereas cis ‐forms are the first‐order transition structures. The relative energies of the cis ‐conformers at MP 2/6‐31G**// HF /6‐31G* + 0.9 zero point energy ( ZPE ) level are equal to 47.4, 51.7, and 59.7 kJ mol −1 for TB, B, and DTB, respectively. Because of relatively large dipole moments, cis ‐conformers are predicted to be stabilized in polar solvents.