ISSN:
0020-7608
Keywords:
Computational Chemistry and Molecular Modeling
;
Atomic, Molecular and Optical Physics
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
We report a comparison of theoretical and experimental proton affinities at nitrogen and oxygen sites within a series of small molecules. The calculated proton affinities are determined using the semiempirical methods AM1, MNDO, and PM3; the ab initio Hartree-Fock method at the following basis levels: 3-21G//3-21G, 3-21+G//3-21G, 6-31G*//6-31G*, and 6-31+G(d, p)//6-31G*; and Møller-Plesset perturbation calculations: MP2/6-31G*//6-31G*, MP3/6-31G*//6-31G*, MP2/6-31G+(d, p)//6-31G*, MP3/6-31G+(d, p)//6-31G*, and MP4(SDTQ)/6-31G+G(d, p)//6-31G*. The semiempirical methods have more nonsystematic scatter from the experimental values, compared to even the minimal 3-21G level ab initio calculations. The thermodynamically corrected 6-31G*//6-31G* proton affinities provide acceptable results compared to experiment, and we see no significant improvement over 6-31G*//6-31G* in the proton affinities with any of the higher-level calculations. © 1992 John Wiley & Sons, Inc.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/qua.560430606
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