Zm. Hu et Cg. Zhan, NATURAL HYBRID ORBITAL STUDY OF THE C-H S TRETCHING FREQUENCIES IN HYDROCARBONS AND HETEROSUBSTITUTED HYDROCARBONS, Huaxue xuebao, 52(7), 1994, pp. 652-657
As a result of earlier interest in the calculation of the C-H nuclear
spin-spin coupling constants and its correlation with the C-H stretchi
ng frequencies in hydro and heterosubstituted hydrocarbons, a novel ge
neral relationship for the calculation of the C-H stretching frequenci
es is proposed in this paper. The proposed relationship has been emplo
yed to calculate the C-H stretching frequencies (nu(CH)) for a series
of hydrocarbons, fluorosubstituted hydrocarbons and substituted aldehy
des by use of the CNDO/2 molecular orbital approximation and the natur
al hybrid orbital scheme. It is shown that the C-H stretching frequenc
ies are directly proportional to the s-character of the corresponding
C atom in hydrocarbons. But for heterosubstituted hydrocarbons, the ne
t charges of atoms C and H, or the polarity of the C-H bond, become a
significant factor. The calculated results may also be utilized to acc
ount for other factors affecting nu(CH), such as steric effect, cis-tr
ans geometry and substituted effects etc.. Some discussions concerning
the calculated results are also reported.