標題: Cycloadditions of 16-electron 1,3-dipoles with ethylene. A density functional and CCSD(T) study
作者: Su, MD
Liao, HL
Chung, WS
Chu, SY
應用化學系
Department of Applied Chemistry
公開日期: 3-九月-1999
摘要: The 1,3-dipolar cycloaddition (DC) reactions of ethylene with nitrile ylide (CNC), nitrile imine (CNN), nitrile oxide (CNO), diazomethane (NNC), azine (NNN), and nitrous oxide (NNO) in the gas phase were examined using the density functional theory and CCSD(T) calculations. All of the structures, including the precursor complexes;and the transition structures, were completely optimized at the B3LYP/6-31G* level with single-point energies evaluated at CCSD(T)/6-311G**. The theoretical results suggest that the activation energies for the DC reactions of nitrile-type molecules (CNC, CNN, and CNO) are small (5.1-11 kcal/mol) and these reactions are very exothermic (-77 to -46 kcal/mol). In contrast, the DC reactions of NNC, NNN, and NNO are less exothermic (-39 to -6.0 kcal/mol) and have larger activation barriers (13-29 kcal/mol). Moreover, this work shows that the configuration mixing (CM) model based on Press and Shaik's theory can successfully predict the relative ordering of the activation energy and reaction enthalpies of DC reactions; Combining our theoretical calculations and the CM model, the following conclusion emerges: a 16-electron 1,3-dipole reactant with more electropositive substituents at the terminal positions will possess a smaller singlet-triplet splitting. This will facilitate cycloaddition with the dipolarophile and will result in a larger exothermicity.
URI: http://dx.doi.org/10.1021/jo990504j
http://hdl.handle.net/11536/31094
ISSN: 0022-3263
DOI: 10.1021/jo990504j
期刊: JOURNAL OF ORGANIC CHEMISTRY
Volume: 64
Issue: 18
起始頁: 6710
結束頁: 6716
顯示於類別:期刊論文


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