Abstract
AbstractThe Rayleigh ratios RH have been measured for the depolarized scattering dilute solutions of N‐ethylacetamide (EA), N‐methylpropionamide (MP), and N‐acetyl‐pyrrolidine (AP) in P‐dioxane, and dilute aqueous solutions of N‐methylacetamide (MA), N,N‐dimethylacetamide (DMA), EA, and MP. Squares of the optical anisot‐ropies γ of the amides are obtained through extrapolation of these mesurements to infinite dilution. Values of γ2 found for EA and MP in dioxane are in good agreement with calculations based principally on the previously evaluated polarizability tensor of the amide group in conjunction with CC and CH bond polarizabilities. The calculations also involve averaging over all conformations, each being weighted according to the estimated conformational energy. The mean‐squared optical anisotropies (γ2) of the oligoglycines and oligoalanines are calculated by similarly averaging over all skeletal conformations. The anistropic polarizability tensor \documentclass{article}\pagestyle{empty}\begin{document}$ \hat \alpha $\end{document} for the prolyl structural unit magnified image is derived for γ2 for AP. The much larger optical anisotropies exhibited by the amides when dissolved in water as compared with those observed in dixane are discussed.
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