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N ‐arylamides and N ‐arylcarbamates NCO internal rotation barrier study by molecular modeling
Author(s) -
Grasel Fábio Dos Santos,
De Oliveira Tiago Charão,
Fontoura Luiz Antonio Mazzini,
Da Cruz Rigotti Italo José,
Netz Paulo Augusto
Publication year - 2011
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.23151
Subject(s) - internal rotation , chemistry , rotation (mathematics) , chemical physics , geometry , mathematics , engineering , mechanical engineering
Amides and carbamates present an energetic barrier associated to NC(O) bond rotation, which determines two different equilibrium geometries. In this work, the conformational equilibrium of formanilide, acetanilide, methyl and t ‐butyl phenylcarbamates, and their N ‐methylderivatives was studied by AM1 and B3LYP/6‐31G(d,p) calculations. The effect of aryl p‐ substituents (MeO, Me, Cl, Br, CN, and NO 2 ) was also studied. Amide barriers were found by DFT calculation between 12 and 21 kcal/mol. Carbamates, on the other hand, showed barriers between 11 and 15 kcal/mol. AM1 underestimates the energetic barriers and provides values around half those obtained by B3LYP/6‐31G(d,p) calculations. Electron withdrawing substituents on aryl group decrease the barrier. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012