Vibrational analysis of substituted benzonitriles. I. Vibrational spectra, normal coordinate analysis and transferability of force constants of monohalogenated benzonitriles.
The Raman and Fourier--transform infrared spectra of p- and o-fluorobenzonitriles, p-, m- and o-chlorobenzonitriles and p-, m- and o-bromobenzonitriles were measured. Raman polarisation measurements were made wherever possible. A normal coordinate analysis was carried out for both the in-plane and out-of-plane vibrations of these molecules along with m-fluorobenzonitrile using a 71-parameter modified valence force field. An overlay least-squares-technique was employed to refine the force constants using 269 frequencies of nine molecules. The reliability of the force constants so obtained was tested by making a zero-order calculation for both in-plane and out-of-plane vibrations of p-, m- o-dicyanobenzenes and their deuterated isomers; 2-chloro, 6-fluorobenzonitrile, s-trichlorobenzonitrile, p- and m-methoxybenzonitriles and m-nitrobenzonitrile; and for the in-plane vibrations of p-, m-, o-aminobenzonitrile and 2-chloro, 5-aminobenzonitrile. Unambiguous vibrational assignments of all the fundamentals were made using the potential energy distributions and eigenvectors.
Kumar
A P
AP
Department of Physics, Kakatiya University, Vidyaranyapuri, Warangal, India.
Rao
G R
GR
D006219:Halogens / Q000737:chemistry; D008956:Models, Chemical; D009570:Nitriles / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D014732:Vibration
D006219:Halogens; D009570:Nitriles; C014356:benzonitrile