CONFORMATIONAL STABILITY OF TRANS-1-FLUORO-2-BUTENE

Variable temperature infrared studies of trans-1-fluoro-2-butene, tran s-CH3HC=CHCH2F, have been carried out with the sample dissolved in liq uid xenon. These spectral data have been interpreted on the basis that the molecule exists in the fluid phases as a mixture of the synclinal (fluorine atom oriented cis to the double bond) and anticlinal (gauch e) conformations and the synclinal conformer is more stable by 130 +/- 40 cm(-1) (372 +/- 114 cal/mol). Ab initio calculations have been car ried out utilizing the RHF/6-31G and MP2/6-31G* basis sets which pred icted the cis rotamer more stable than the gauche form which is consis tent with the experimental results.