Transition-state electronic structures in SN2 reactions

1989 ◽  
Vol 111 (5) ◽  
pp. 1575-1579 ◽  
Author(s):  
Zheng Shi ◽  
Russell J. Boyd
Keyword(s):  
Transition State ◽  
Electronic Structures ◽  
Sn2 Reactions

Relative reactivity of three oxygen lone pairs of an α-nucleophile in SN2 reactions

1990 ◽  
Vol 68 (7) ◽  
pp. 1182-1185 ◽  
Author(s):  
J. L. Wolk ◽  
M. R. Hajnal ◽  
S. Hoz ◽  
R. M. Tarkka ◽  
E. Buncel
Keyword(s):  
Transition State ◽  
Lone Pair ◽  
Am1 Method ◽  
Activation Barriers ◽  
Molecular Plane ◽  
Relative Stabilities ◽  
Sn2 Reactions ◽  
Lone Pairs ◽  
Stability Order ◽  
Reactivity Order

The SN2 reaction of H2C=NO− with CH3Cl was investigated at the AM1, STO-3G, and 6-31 + G* levels. Three modes of approach of CH3Cl to the oxygen of the nucleophile were examined: syn and anti to the lone pair on the nitrogen in the molecular plane, and an approach along the π system of the oximate anion. The AM1 method differed markedly from the two abinitio methods, both in the reactivity order of the three geometries as well as in the relative stabilities of the products. The reactivity order calculated at the STO-3G and the 6-31 + G* levels was syn > π > anti (AM1 order: anti > syn > π). Product stability order calculated by the two abinitio methods was syn > anti > π (AMI order: anti > syn > π). Excellent agreement was obtained between percent bond elongations at the transition state predicted by the equation suggested by Shaik, Schlegel, and Wolfe, and the activation barriers calculated at the 6-31 + G* level. The relevance of the calculations with respect to the α-effect is also discussed. Keywords: oxygen lone pairs, aximate, SN2, abinitio.

scholarly journals Computational Study of Electronic Influence of Guanidine Substitution on Diels-Alder Reactions of Heterocyclic Dienes

2019 ◽  
Vol 92 (2) ◽  
pp. 279-286
Author(s):  
Ivana Antol ◽  
Luka Barešić ◽  
Zoran Glasovac ◽  
Davor Margetić
Keyword(s):  
Transition State ◽  
Quantum Chemical Calculations ◽  
Electronic Structures ◽  
Quantum Chemical ◽  
Computational Study ◽  
Cycloaddition Reaction ◽  
Diels Alder ◽  
Reaction Barriers ◽  
Reactivity Order

Quantum-chemical calculations of cycloaddition properties of cyclic heterodienes substituted with guanidine functionality were carried out. Molecular and electronic structures of series of dienes (pyrrole, furan, thiophene, isoindole and 1,3-butadiene) were calculated and reactivity order established on the basis of FMO theory. Transition state calculations of model [4+2] cycloaddition reaction with acetylene indicate that guanidine substitution influences reaction barriers in moderate extent (up to ~4 kcal mol–1). The substitution position plays an important role on the sign and magnitude of the effect and protonation of nitrogen possessing substituents increases reactivity of dienes.

SN2 reactions in the gas phase. Structure of the transition state

1974 ◽  
Vol 8 (1) ◽  
pp. 77-79 ◽  
Author(s):  
Ralph C. Dougherty ◽  
J. Dalton ◽  
J. David roberts
Keyword(s):  
Transition State ◽  
Gas Phase ◽  
Phase Structure ◽  
Sn2 Reactions ◽  
Gas Phase Structure
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