CEQUINOR   05415
CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Unidad Ejecutora - UE
artículos
Título:
Gas-Phase Structure, Rotational Barrier and Vibrational Properties of Methyl Methanethiosulfonate, CH3SO2SCH3: An Experimental and Computational Study
Autor/es:
M. E.TUTTOLOMONDO; A. NAVARRO; T. PEÑA RUIZ; E. L. VARETTI; S. A. HAYES; D. A. WANN; H. E. ROBERTSON; D. W. H. RANKIN; A. BEN ALTABEF
Revista:
JOURNAL OF PHYSICAL CHEMISTRY A
Referencias:
Año: 2007 vol. 111 p. 9952 - 9960
ISSN:
1089-5639
Resumen:
The molecular structure
of methyl methanethiosulfonate, CH3SO2SCH3, has
been determined in the gas phase from electron-diffraction data supplemented by
ab initio (HF, MP2) and DFT calculations using 6-31G(d), 6-311++G(d,p) and
6-311G(3df,3pd) basis sets. Both experimental and theoretical data indicate
that although both anti and gauche conformers are possible by
rotating about the SS bond, the preferred conformation is gauche. The barrier to internal rotation in the CSSC skeleton has
been calculated using the RHF/6-31G(d), MP2/6-31G(d) and B3LYP/6-31G(d)
methods, as well as MP2 with a 6-31G(3df) basis set on sulfur and 6-31G(d) on
C, H and O. A six-fold decomposition of the rotational barrier has been
performed in terms of a Fourier-type expansion, enabling us to analyze the nature of the potential function,
showing that the coefficients V1 and V2 are the dominant terms; V1 is associated with
nonbonding interactions and V2
with hyperconjugative interactions. A natural bond orbital analysis showed that
the lone pair ® σ* hyperconjugative
interactions favor the gauche conformation. Furthermore, the
infrared spectra for the liquid and solid phases and the Raman spectrum for the
liquid have been recorded and the observed bands assigned to the vibrational
normal modes. The experimental vibrational data, along with calculated theoretical
force constants, were used to define a scaled quantum mechanical force field
for the target system that enabled us to estimate the measured frequencies with
a final root-mean-square deviation of 6 cm1.