Matrix-isolation FT-IR spectra and theoretical study of dimethyl sulfate.
The preferred conformations of dimethyl sulfate and their vibrational spectra were studied by matrix-isolation FT-IR spectroscopy and theoretical methods (DFT and MP2, with basis sets of different sizes, including the quadruple-zeta, aug-cc-pVQZ basis). Conformer GG (of C2 symmetry and exhibiting OSOC dihedral angles of 74.3 degrees ) was found to be the most stable conformer in both the gaseous phase and isolated in argon. Upon annealing of the matrix, the less stable observed conformer (GT; with C1 symmetry) quickly converts to the GG conformer, with the resulting species being embedded in a matrix-cage which corresponds to the most stable matrix-site for GG form. The highest energy TT conformer, which was assumed to be the most stable conformer in previous studies, is predicted by the calculations to have a relative energy of ca. 10 kJ mol-1 and was not observed in the spectra of the matrix-isolated compound.
Borba
Ana
A
Department of Chemistry, University of Coimbra, Coimbra P-3004-535, Portugal.
Gómez-Zavaglia
Andrea
A
Simões
Pedro N N L
PN
Fausto
Rui
R
D001128:Argon / Q000737:chemistry; D008958:Models, Molecular; D008962:Models, Theoretical; D008968:Molecular Conformation; D016011:Normal Distribution; D012984:Software; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013463:Sulfuric Acid Esters / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics
D013463:Sulfuric Acid Esters; D001128:Argon; C007482:dimethyl sulfate