The Sense and Magnitudes of C-H Bond Moments and Absolute Infrared Intensities of Hydrocarbons

Abstract

The study of polar properties, viz., mean bond dipole moment and its derivatives, and other bond charge parameters of CH bonds in hydrocarbons through infrared intensity analysis is one of the major interests in molecular spectroscopy. A s such, the behavior of a molecule o r the nature of a chemical bond has been one of the most difficult and intricate subjects that has puzzled both experimentalists and theoreticians for many years. The most important but also the unfortunate part of the research activities centered around molecular spectra, structures, and properties concerns the fact that the “nature and behavior” of molecules o r bonds are far out of the reach of experimental tools o r mathematical methods; they cannot be directly recorded by instruments or forecast within the framework of a theory with authenticity because of the inherent drawbacks of the various approaches applied. However, the interaction of a molecular system with any of these approaches reflects a t least a clue to the perception of the solution to a problem. Some problems may be discussed safely, i.e., the problem of sense and magnitudes of the CH bond moments, the nature of the CH bond dipole, and the dependence of infrared intensities on them in hydrocarbons. These form the basic theme of this presentation.