Stretching frequency, CH - isolated

McKean, D. C., J. E. Boggs, and L. Schafer. 1984. CH Bond Length Variations Due to the Intramolecular Environment a Comparison of the Results Obtained by the Method of Isolated CH Stretching Frequencies and by Ab Initio Gradient Calculations. J. Mol. Struct. 116, 313-330. 

Adiabatic frequencies of 1 are compared in Table 20 with those of some other hydro-carbons The adiabatic CC frequency is about 80 and the adiabatic CH stretching frequency about 100 cm larger than the corresponding values for cyclohexane. Compared to ethene, adiabatic CH stretching frequencies are almost identical, which is in line with the high dissociation energy of the CH bond of 1 (see Section V. E). The same observation has been made by McKean using isolated CH frequencies obtained by appropriate deuteration of 1 ... 

At attempt was made (101) to test the isolated vibration hypothesis [Sec. Ill A, 1(b)] with this system, by comparing the vibrational frequencies in the CH stretching and bending region of hexa-methylbenzene and its stable chloranil complex. Equation (III-10) requires a net downward shift of 100 cm. , shared among the three CH stretching and three CH bending modes. It can be seen... 

The C=S group in ethylene trithiocarbonate has a C=S stretch band at 1064 cm" as seen in spectrum 218 in Ch. 13. This can be compared with the C=0 stretch in ethylene carbonate at 1804 cm in spectrum 217 in Ch. 13. In both cases, the high frequency C=X group is attached to two low frequency C—X groups. This means that the single bonded X atoms are nearly stationary, dius isolating the double bond vibration. 

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