{sup 13}C chemical shift tensor of the isopropyl cation

Journal Article · Wed May 01 04:00:00 EDT 1996 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja953645l· OSTI ID:249678

Nicholas, J B ^[1]; Xu, T; Barich, D H; Torres, P D; Haw, J F ^[2]

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1. Pacific Northwest National Lab., Richland, WA (United States)
2. Texas A&M Univ., College Station, TX (United States)

A characteristic common to all carbenium shift calculations reported thus far is that they have discussed only the isotropic chemical shift which is observable in solution. We have recently reported measurements of the principal components. {delta}{sub 11}, {delta}{sub 22}, and {delta}{sub 33}, of the {sup 13}C shift tensors for various carbenium ions synthesized on solid acids including zeolites and metal halide powders. As demonstrated by the work of Facelli and Grant, agreement between calculated and experimental values of all three principal components is a more stringent test of methodology than agreement of the averages. We investigated the sensitivity of the shift calculations to reasonable variations in bond distances and angles and found no remarkable sensitivity. At the suggestion of a referee, we also considered pyramidalization of the cation. We optimized the structure of its water adduct (i.e., protonated 2-propanol) at Mp2/6-311+G{sup **}, froze the geometry, and removed H{sub 2}O. The isotropic {sup 13}C shift of the pyramidally distorted center so generated was 431 ppm. We therefore investigated possibilities other than relaxation of the geometry. The principal components of a heteroatom-substituted secondary cation were recently reported. In this communication we have reported the first such measurement for a nonsubstituted secondary carbenium ion. 24 refs., 2 figs., 1 tab.

• DOE Contract Number: FG03-93ER14354
• OSTI ID: 249678
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 17 Vol. 118; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
99 GENERAL AND MISCELLANEOUS
CALCULATION METHODS
CARBON 13
CATIONS
CHEMICAL SHIFT
ISOPROPYL RADICALS
MOLECULAR MODELS
NMR SPECTRA
TENSORS