Conformational analysis of some N,N-diethyl-2-[(4 '-substituted) phenylthio] acetamides

Conformational analysis of some N,N-diethyl-2-[(4 '-substituted) phenylthio] acetamides

Author Vinhato, Elisangela Autor UNIFESP Google Scholar
Olivato, Paulo R. Google Scholar
Zukerman-Schpector, Julio Google Scholar
Dal Colle, Maurizio Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Universidade de São Paulo (USP)
Universidade Federal de São Carlos (UFSCar)
Univ Ferrara
Abstract The conformational analysis of some N,N-diethyl-2[(4'-substituted)phenylthio]acetamides bearing the substituents OMe 1, Me 2, H 3, Cl 4, Br 5 and NO2 6, was performed by v(co) IR analysis, along with B3LYP/6-311++G(d,p) and Polarisable Continuum Model (PCM) calculations, as well as NBO analysis for 1, 3, and 6 and X-ray diffraction for 4. the results of the calculations indicated the existence of two stable conformation pairs, i.e. gauche (anti; syn) (most stable) and cis (anti; syn) in the gas phase. the gauche conformers were less polar with respect to the cis ones for 1 and 3, but more polar for 6. the most intense IR carbonyl doublet component observed at the lower frequency can be ascribed to the gauche conformers g(anti; syn) for 3-6 in n-C6H14, which is in agreement with the gauche and cis relative stabilities and frequencies resulting from the PCM calculations. Similarly, the single IR band for 1 and 2 in n-hexane may be attributed to the gauche conformers. the PCM calculations compared well with the IR data for the compounds in solution, showing that there is a progressive increase of the cis/gauche population ratio as the solvent polarity increases. the NBO analysis indicated that the gauche(anti; syn) conformation in the gas phase was stabilized by the relevant Lp(s4) pi(*)(c2)=cn sigma(*)(C3-s4), sigma(c3-S4) 21, iCa2.31 > 03_S4, and LPol a* a 1-H28 orbital interactions, which were absent in the cis(anti; syn) conformer. On the contrary, the cis conformer for derivatives 1, 3, and 6 were stabilized by the aa. Cr c2 N5 orbital interaction (through bond coupling), along with the additional LP01 crs4-cio interaction for 6. Moreover, the electrostatic repulsion between the C8 S' and C8*=08- dipoles (Repulsive Field Effect) contributed to both the larger destabilization and increase of the vco frequency of the cis conformer with respect to the gauche conformer. X-ray single crystal analysis indicates that compound 4 assumes the c2(anti) conformation in the solid state, which is the conformation obtained by compound 6 in the gas phase. To obtain the largest energy gain, the molecules were arranged in the crystal in a six-molecules synthon mediated by C-H center dot center dot center dot O and Cl center dot center dot center dot Cl interactions, where the chlorine atoms were related by a crystallographic inversion center. (C) 2013 Elsevier B.V. All rights reserved.
Keywords Conformational analysis
Infrared spectroscopy
Theoretical calculations
X-ray diffraction analysis
Solvent effect
Language English
Sponsor Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Grant number CAPES: 808/2009
Date 2013-11-01
Published in Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy. Oxford: Pergamon-Elsevier B.V., v. 115, p. 738-746, 2013.
ISSN 1386-1425 (Sherpa/Romeo, impact factor)
Publisher Elsevier B.V.
Extent 738-746
Access rights Closed access
Type Article
Web of Science ID WOS:000324152700093

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