Abstract
The {sup 13}C shielding of the isotopomers CH{sub 3}Cl, CH{sub 2}DCl, CHD{sub 2}Cl, and CD{sub 3}Cl has been calculated for a range of temperatures from an self-consistent field (SCF) shielding surface computed by Buckingham and Olegario. It is found that each successive deuterium substitution increases the shielding by about 0.19 ppm and that a very slight nonadditivity occurs. The principal factor which governs the nuclear motion correction for each isotopomer is the stretching of the bonds with both first- and second-order terms being significant. Angle bending contributions are very small at first order but quite substantial at second order. Not only should the {sup 13}C-isotope shifts in this experimentally uninvestigated series be easily measured but the temperature dependence of the shielding in any one isotopomer should be observable provided that careful measurements are made. The {sup 13}C-shielding difference between CH{sub 3} {sup 35}Cl and CH{sub 3} {sup 37}Cl has also been calculated and is found to agree well with experiments. 28 refs., 4 tabs.
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