# MICROWAVE INVESTIGATION OF C-H HYDROGEN BONDING INTERACTIONS IN THE DIMETHYL ETHER - OCS DIMER

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 Title: MICROWAVE INVESTIGATION OF C-H HYDROGEN BONDING INTERACTIONS IN THE DIMETHYL ETHER - OCS DIMER Creators: Newby, Josh J.; Peebles, Rebecca A.; Peebles, Sean A. Issue Date: 2004 Publisher: Ohio State University Abstract: The rotational spectrum of a weakly bound dimer formed between dimethyl ether and OCS has been observed by Fourier-transform microwave spectroscopy. The rotational constants of the normal isotopic species are found to be $A = 4069.4106(23)$ MHz, $B = 1431.7413(7)$ MHz and $C = 1074.2925(5)$ MHz and the dipole moment components are $\mu_{a} = 1.3046(25) D$ and $\mu_{b} = 0.8159(35) D$. The rotational constants and dipole moment components are consistent with a heavy atom planar structure in which the OCS lies across the $C_{2}$ axis of the dimethyl ether (the $O = C\ldots O$ angle is estimated to be about $83^{\circ}$ by ab initio calculation); the oxygen atom of OCS appears to interact with one of the methyl group hydrogen atoms. Isotopic shifts in the spectra of the $DME-O^{13}CS$ and $DME-OC^{34}S$ isotopomers have been found to be consistent with this structure. Ab initio optimizations at the $MP2/6-311++G(2d,2p)$ level will be presented and shown to give very good agreement with the rotational constants obtained from experiment. Description: Author Institution: Department of Chemistry, Eastern Illinois University URI: http://hdl.handle.net/1811/21518 Other Identifiers: 2004-WH-14