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Show 110 A. MOLECULAR THEORIES OF" OR})' AND CD Classical Pasteur,ll Ie Bel12 and van't Hoff13- developed the present conception of molecular structure and pr-oposed he theory' connecting - optical activity with the existence of non-stiperimposable asymmetry in the molecule, a theory confirmed by an enormous amount mental work carried out set over the last hundred'yearso of experi- Their work stage for ttua development of physical theories connecting the optical rotation and circular- dichroism with speci,fic molecular mechanisms. The first classical model of 1:>Y Drude .14 in 1892 In hs': model, the assumed in the classical oscillators theory According ,to, Dt'ude 0 optical" 'activity w'as", proposed linear oscillating' charges t of 'dispersion. "are if a replaced"by helical '"charged partice is displaced -along a helical path, th translatory motion gives'rise-to an electric 'dipole moment and the rotatory The two moments for parallel for-a right handed helix and antiparallel left-handed helixQ a - are motion'toa'magnetic dipole moment. The expression Drude derived' may -be "written R. 4> = L--- i ")..'j. where A is the _ ").. wavelength of the incident light. Ai is'the wavelength |
