A theoretical study of diethyl ketone
1969; Elsevier BV; Volume: 25; Issue: 6 Linguagem: Inglês
10.1016/s0040-4020(01)82691-0
ISSN1464-5416
AutoresRobert Earl Davis, C. R. Chuang Pfaffenberger, D. Grosse, J. Morris,
Tópico(s)Molecular spectroscopy and chirality
ResumoThe IR spectrum of diethyl ketone has been computed starting with the force constants (both diagonal and off-diagonal elements) obtained by normal coordinate analysis of acetone and a normal paraffin. The position of the carbonyl frequency, νCO, is accurately computed in the gas phase. The molecule has then been deformed (G-matrix variation) and the spectrum computed. It is concluded that purely geometric effects can shift the νCO by sizable amounts, upwards of 12 cm−1. In other calculations the maximum amount of steric effect on the carbonyl vibration has been estimated to be almost 30 cm−1. This estimate has been made by using only the diagonal elements of the F-matrix assuming that the off-diagonal elements represent non-bonded interactions. This is a reasonable assumption. It has been concluded that the carbonyl stretching frequency must be used with extreme caution as a model for carbonium ion reactions. In particular the position of νCO is determined by numerous factors other than just simple angle strain.
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