10min:
STRUCTURE DETERMINATION OF TWO STEREOISOMERS OF SEVOFLURANE DIMER BY CHIRPED PULSE FTMW SPECTROSCOPY.

NATHAN A. SEIFERT, CRISTOBAL PEREZ, DANIEL P. ZALESKI, JUSTIN L. NEILL, BROOKS H. PATE, Department of Chemistry, University of Virginia, McCormick Rd., Charlottesville, VA 22904-4319; ALBERTO LESARRI, MONTSERRAT VALLEJO, Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, E-47011 Valladolid, Spain; EMILIO J. COCINERO, FERNANDO CASTANO, Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco (UPV/EHU), Campus de Leioa, Ap. 644, E-48080 Bilbao, Spain.

Two stereoisomers of sevoflurane dimer have been detected using chirped pulse FTMW spectroscopy from 2-8 GHz. The identified complexes are distinguished by their differing helicities, and together both isomers form a diastereomeric pair, one being homochiral (RR/SS) and the other heterochiral (RS/SR). For both isomers, all 8 13C isotopologues have been assigned, and two 18O isotopologues have also been detected for the homochiral isomer, for a total of 18 isotopologues. MP2/6-311++g(d,p) calculations predict the heterochiral isomer as 1.2 kJ mol-1 above the homochiral species, which is consistent with the observed relative intensities between the two species. A summary of these microwave results, including a comparison between the Kraitchman and ab initio structures, will be presented.