			15min:

MICROWAVE SPECTROSCOPIC INVESTIGATIONS OF THE C--H cdots

CONTAINING COMPLEXES CH₂F₂ cdots

PROPYNE AND CH₂ClF cdots

PROPYNE.

REBECCA A. PEEBLES, SEAN A. PEEBLES, CORI L. CHRISTENHOLZ, ANTHONY A. ERNST AND YASSER J. DHAHIR, Department of Chemistry, Eastern Illinois University, 600 Lincoln Ave., Charleston, IL 61920.

The spectra of the CH₂F₂ cdots propyne and CH₂ClF cdots propyne complexes have been studied by chirped-pulse and resonant cavity Fourier-transform microwave spectroscopy and by ab initio calculations at the MP2/6-311++G(2d,2p) level. Both complexes contain C--H cdots contacts, with the halogen atoms angled towards the methyl group end of the propyne. While CH₂F₂ cdots propyne has C_s symmetry, CH₂ClF cdots propyne has C₁ symmetry, with the fluorine and chlorine atoms straddling the propyne.

Investigation of four single ¹³C and the DC equiv CCH₃ isotopologues in CH₂F₂ cdots propyne has allowed a detailed structural determination, while only the ³⁵Cl and ³⁷Cl isotopologues have so far been assigned for CH₂ClF cdots propyne. Experimental data will be compared with ab initio results and with the analogous acetylene complexes, both of which have C_s symmetry structures, with double C--H cdots interactions.