HOW PREDICTABLE ARE IR TRANSITION-MOMENT - VIBRATIONAL TRANSITIONS INPROPENE AND DEUTRATED PROPENES

Transition moment directions of mid-infrared transitions in four isoto pomers of propene, CH2=CHCH3, CH2=CDCH3, CD2=CHCD3, and CD2=CDCD3, hav e been determined from linear dichroism spectra recorded in stretched polyethylene as solvent. The results were compared with expectations b ased on bond directions and with results of ab initio calculations at levels of approximations ranging up to CCSD/6-311G*. The former proce dure is found to be unreliable, even for high frequency vibrations. Wi th rare exceptions, the highest levels of ab initio theory agree with the experimental directions to within about +/-20 degrees, and for int ense transitions, to within the experimental uncertainty of about +/-( 5-10)degrees.