Isolated CH stretching frequencies and bond properties in CH 3CF 3, CH 2(CF 3) 2 and CH(CF 3) 3

Abstract

The CH stretching frequencies recently reported in CHD 2CF 3, CHD(CF 3) 2 and CH(CF 3) 3 are used to show that the influence of an αCF 3 group on CH bond strength is irregular and very different from that of αCH 3. The value in CHD 2CF 3 is slightly higher than expected from the β-effects of individual CF bonds as found in EtF. An attempt is made to discuss the strength variations in terms of the Bellamy—Mayo model. Predictions are made of CH bond lengths and dissociation energies throughout, and ∠HCH in CH 3CF 3 is estimated.