Infrared and Raman spectra were obtained for 2-ethyl-1-butene and infr
ared spectra were obtained for 3-pentanone. Normal coordinate calculat
ions were made for all three possible conformers of each compound and
the resulting vibrational assignments and force constants are given in
this paper. Molecular mechanics and low-level ab initio molecular orb
ital calculations were also made for all the conformers. The results s
upport the existence of three conformers of the alkene and two conform
ers of the ketone.