Urey-Bradley force field of 4-ethylpyridine

A normal coordinate analysis is carried out to obtain the Urey-Bradley forc e constants for I -ethylpyridine (4-etpy) assuming an under C-2 upsilon poi nt group. These constants are adjusted to fit the observed frequencies for 4-etpy and its deuterated species. The calculated frequencies allowed the v ibrational assignments of the normal modes of 4-etpy. These assignments are confirmed by the calculations of the potential energy distributions on 4-e tpy. Additional information is obtained from the vibrational spectra of Cd (4-etpy)(2) M (CN)(4) (M=Cd, Hg) and calculated wavenumbers of metal (Cd) b onded 4-etpy. It is shown that the ring vibrations in pyridine are to be ef fected upon metal substitution. These results have also provided certainty for the vibrational assignments. (C) 1999 Elsevier Science B.V. All rights reserved.