As derivadas de momento dipolar e as intensidades vibracionais dos difluoroetilenos

AUTOR(ES)

Roy Edward Bruns

DATA DE PUBLICAÇÃO

1979

RESUMO

Using the F and G intensity sum rules, the absolute vibrational intensities measured by Kagel for vic-, cis-, and trans-C2HxD2-xF2 (x = 1, 2) are found to be free of large systematic experimental error. Preferred values for the dipole moment derivatives with respect to the symmetry coordinates of these molecules based on approximate semiempirical MO results are reported, resolving for alI practical purposes the sign ambiguity in these derivatives with respect to normal coordinates. Effective charges calculated from polar tensors using these preferred values are found to be consitent with the values calculated for these quantities using the G intensity sum rule. Both the CNDO and MINDO/3 MO methods are found to be reliable in predicting the signs of these derivatives although their magnitudes differ substantially depending on the theory applied. The theoretical derivatives are interpreted in terms of chemical valency concepts. The limitations of such interpretations are stressed. CNDO and MINDO/3 estimates of the directional properties of the in plane derivatives of trans-difluoroethylene are found to be quite inadequate. Empirical estimates of various dipole moment derivatives of vic-C2H2CI2 are presented.

ASSUNTO(S)

fisico-quimica momentos dipolares

Documentos Relacionados

• Analise de componentes principais das derivadas do momento dipolar
• Estudos teoricos de modelos de eletronegatividade para intensidades vibracionais
• Interpretação de parametros de intensidades vibracionais e previsão de espectros no infravermelho
• Investigação de energias de ionização e intensidades vibracionais (IV) utilizando o modelo potencial simples
• Estudo e aplicações dos tensores polares e das cargas elefetivas na analise das intensidades das bandas de espectros vibracionais - rotacionais