The effect of the weak long-range interaction on the shielding constant is considered for a pair of interacting atoms. The asymptotic long-range effects are proportional to R-" (where R is the interatomic distance). For the anisotropy of the shielding tensor n = 3, for the trace n = 6 for two neutra
Effects of molecular association on the NMR shielding constants in acetonitrile
β Scribed by Karol Jackowski
- Publisher
- Elsevier Science
- Year
- 1992
- Tongue
- English
- Weight
- 279 KB
- Volume
- 194
- Category
- Article
- ISSN
- 0009-2614
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β¦ Synopsis
Ab initio results for the shielding constants in acetonitrile were calculated for the isolated molecule, the antiparallel dimer and the antiparallel trimer. It was found that the association effects calculated at the SCF approximation could be successfully compared with experimental NMR gas-to-liquid shifts. Calculated anisotropies of ~ 3C and ~SN shielding constants for the cyano group are also consistent with the latest experimental results.
π SIMILAR VOLUMES
It is shown that accurate estimates of the true nuclenr magnetic shieIding constsnts in atoms czn be obtained with considerable ease from spproximate Hartree-Fock values. Extension of this estimation procedure to molecular systems is discussed. ## * Aided by a research grant tu The Johns Hopkins
## Abstract Solvent effects on the nitrogen NMR shieldings of indolizine and three azaindolizines are presented for a range of thirteen solvents. The results are discussed in terms of hydrogenβbonding an solvent polarity effects. βPyridineβtypeβ nitrogen atoms show a much larger range of solvent ef