Strain-Free Transition States in the Formation of Strained Rings: An ab Initio Study of Thiirane, Thietan, and Tetrahydrothiophene

1995 ◽  
Vol 60 (21) ◽  
pp. 6731-6736 ◽  
Author(s):  
Scott Gronert ◽  
Joseph M. Lee
Keyword(s):  
Ab Initio ◽  
Transition States ◽  
Ab Initio Study ◽  
Free Transition

Ab Initio Study of Solvent Effects on Rate of 1,3-Dipolar Cycloadditions of Benzonitrile Oxide and Various Dipolarophiles

2003 ◽  
Vol 2003 (2) ◽  
pp. 91-95 ◽  
Author(s):  
E. Rajaeian ◽  
M. Monajjemi ◽  
M.R. Gholami
Keyword(s):  
Hydrogen Bonding ◽  
Oxygen Atom ◽  
Water Molecule ◽  
Ab Initio ◽  
Solvent Effects ◽  
Transition States ◽  
Molecular Orbital Calculations ◽  
Interaction Energies ◽  
Ab Initio Study ◽  
Dipolar Cycloadditions

Ab initio molecular orbital calculations have been used to investigate the structures and the transition states of 1,3-dipolar cycloadditions between benzonitrile oxide with ethylene, cyclopentene, acrylonitrile and tetracyanoethylene in heptane and water: calculations reveal enhanced hydrogen bonding of a water molecule to the transition states for the cycloaddition 1,3-dipolar of reaction of benzonitrile oxide with cyclopentene, the optimal interaction energies being 0.7 kcal/mol more favourable for hydrogen bonding to the oxygen atom in the transition states than for the reactants.

scholarly journals Ab initio Study of Nucleophilic Aromatic Substitution of Polyfluorobenzene

1999 ◽  
Vol 23 (9) ◽  
pp. 528-529
Author(s):  
Kiyoshi Tanaka ◽  
Makoto Deguchi ◽  
Satoru Iwata
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Transition States ◽  
Nucleophilic Aromatic Substitution ◽  
Bond Breaking ◽  
Aromatic Substitution ◽  
Ab Initio Study ◽  
Rate Determining Step ◽  
Elimination Mechanism ◽  
The Stability

Calculations at ab initio levels of theory of the nucleophilic aromatic substitution of pentafluoronitrobenzene with amines demonstrate an addition–elimination mechanism (SNAr), with the rate-determining step at the second transition state involving C–F bond breaking, and support the ortho-selectivity of the reactions based on the stability of the second transition states.

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