Vibrational analysis of 1-iodopropane, 1-iodobutane and 1,3-diiodopropane

Normal coordinate calculations were made for the trans and gauche conformations of n-propyl and n-butyl iodides and for the tt, tg and gg conformations of 1,3-diiodopropane. Nineteen force constants of a 48-parameter modified valence force field were adjusted to provide the best fit for 114 frequencies (excluding C-H) of all these conformations except for gg, 1,3-di-iodopropane. The average difference between observed and calculated wavenumbers was 6.6 cm^?. Previous vibrational assignments were revised.