Development of a New Set of Additive Parameters for the Estimation of Geometrical Distortion of Cycloalkanes from C-13 NMR Chemical Shifts

Authors : Emad A. S. Al-hyali

Pages : 479-490

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Publication Date : 9999-12-31

Article Type : Makaleler

Abstract :A previous model for the calculation of C-13 chemical shifts is modified by replacement of 3 parameters representing the p-character of carbon atom in cyclic systems with a single parameter aiming for the development of a new set of parameters with a wide range of application for the calculation of C-13 NMR chemical shifts. The considered systems are cyclohexanes, trans decalins, and a number of hypothetical polycyclic 6-member ring hydrocarbons. The developed parameters include a combination of quantum mechanical and statistical methods. They are based on 2 factors: through bond (electronic) effect represented by the partial electronic charge on the tested carbon, and long-range (steric) effect expressed in terms of proton-proton interactions. The results of this study are compared to those of previous studies and sometimes are preferable.
Keywords : Additivity parameters, C-13 NMR chemical shifts, geometrical distortion, cycloalkanes