Force fields for the vinyl halides

Normal coordinate calculations of vinyl fluoride, chloride, bromide and iodide are reviewed. Modified Valence Force Fields are reported, by making use of published vibrational data of all deuterated isotopic species and observed Coriolis constants. The iterative least-squares procedure used adjusts observed and calculated frequencies and second order Coriolis constants simultaneously, so we introduced a mutual dependency between the two vibrational species A′ and A″. Our calculations suggest frequency reassignments for some isotopic molecules.