Nineteen quantitative relationships are presented which enable the calculation of certain CH wag group frequencies in some substituted benzenes, naphthalenes, and acetylenes. Four involve computer calculation of molecular orbital electron densities and one involves Hammett values. The remaining 14 relationships involve simple functions between different CH wag group frequencies based on electron density relationships. This verifies a general tendency for unsaturated CH wag force constants to be weakened when the total electron density on the carbon of the CH is increased.
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