ISSN:
0192-8651
Keywords:
Computational Chemistry and Molecular Modeling
;
Biochemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Computer Science
Notes:
High-level ab initio calculations {QCISD(T)/6-311 +G**//MP2(fu)/6-31 +G**, with corrections for higher polarization [evaluated at MP2/6-311 +G(3df,2p)] and ΔZPE//MP2(fu)/6-31 +G**, i.e., comparable to Gaussian-2 theory} indicate concerted mechanisms for double- and triple-hydrogen exchange reactions in HF and HCl dimers and trimers, in mixed dimers and trimers containing one NH3, and in mixed dimers of HF, HCl, and NH3 with formic acid. All these reactions proceed via cyclic four- or six-center transition structures, the latter being generally more favorable. Calculated activation barriers (ΔHd̊ at 0 K, kcal/mol) are 42.3 for (HF)2, 20.3 for (HF)3, 41.2 for (HCl)2, 25.6 for (HCl)3, 36.0 for NH3-HF, 10.6 for NH3(HF)2, 19.9 for NH3-HCl, 2.3 for NH3(HCl)2, 9.7 for HCO2H-HF, 7.0 for HCO2H-HCl, and 11.3, for HCO2H-NH3. The barriers are lower for the more ionic systems and when more ion pair character is present. © John Wiley & Sons, Inc.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcc.540141005
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