Ab initio study of insertion of unsaturated carbenes. Transition structure and energy barrier for the H2CC (1A1)+ H2O reaction

1986 ◽  
Vol 0 (10) ◽  
pp. 773-774 ◽  
Author(s):  
Minh Tho Nguyen ◽  
Anthony F. Hegarty
Keyword(s):  
Ab Initio ◽  
Energy Barrier ◽  
Ab Initio Study ◽  
Transition Structure

Bicyclo[2.1.1]hex-1-yl Cation: an Ab Initio Study of the C6H9+ Potential-Energy Surface

1993 ◽  
Vol 46 (8) ◽  
pp. 1301 ◽  
Author(s):  
CH Schiesser
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Gas Phase ◽  
Energy Barrier ◽  
Energy Surface ◽  
Molecular Orbital Theory ◽  
Extensive Investigation ◽  
Ab Initio Study ◽  
Orbital Theory

An extensive investigation of the C6H9+ potential-energy surface by ab initio molecular orbital theory is reported. Calculations at the RHF/6-31G* level of theory predict that the bicyclo[2.1.1]hex-1-yl cation (2b) rearranges to the 3-methylenecyclopentyl cation (7b) with an energy barrier of only 0.3 kJ mol-1. Inclusion of electron correlation in the calculation casts doubt on the gas-phase existence of (2b) which is predicted to rearrange without barrier at the MP2/6-31G* level of theory.

Ab Initio Study of Conformational Properties of (Z,Z,Z)-Cyclonona-1,3,6-Triene

2003 ◽  
Vol 2003 (9) ◽  
pp. 546-548
Author(s):  
Davood Nori-Shargh ◽  
Mostafa Mohammadpour Amini ◽  
Saeed Jameh-Bozorghi ◽  
Nooshin Heydari laalee
Keyword(s):  
Ab Initio ◽  
Energy Barrier ◽  
Density Functional ◽  
Stable Form ◽  
Ab Initio Study ◽  
Ring Inversion ◽  
Functional Theory ◽  
Conformational Properties ◽  
Twist Boat ◽  
Calculated Energy Barrier

Ab initio molecular orbital and density functional theory (DFT) calculations, applied to ( Z,Z,Z)-cyclonona-1,3,6-triene (1) have revealed that the calculated energy barrier for ring inversion of the twist-boat ( C1 symmetry) conformation of 1 as a most stable form is 8.41 kcal mol−1, as calculated by the MP2/6-31G*//HF/6-31G* method

Low-energy barrier B4 ring puckering rearrangement of 1,6-diaza-closo-hexaborane: an ab initio study

2001 ◽  
Vol 11 (4) ◽  
pp. 132-134 ◽  
Author(s):  
Ruslan M. Minyaev ◽  
Vladimir I. Minkin ◽  
Tatyana N. Gribanova ◽  
Andrei G. Starikov
Keyword(s):  
Ab Initio ◽  
Energy Barrier ◽  
Low Energy ◽  
Ab Initio Study ◽  
Ring Puckering

Effect of Substitution for Insertion of CO2 into Epoxides and Aziridines: An Ab Initio Study

2020 ◽  
Vol 73 (1) ◽  
pp. 30
Author(s):  
Yunhan Yang ◽  
Fenji Li ◽  
Cuicui Yang ◽  
Lijuan Jia ◽  
Lijuan Yang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Free Energy ◽  
Reaction Mechanism ◽  
Ab Initio ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Concerted Mechanism

The insertion of CO2 into epoxides and aziridines has been studied using density functional theory (B3LYP) and ab initio (MP2) methods, and the effect of substitution for the two reactions are further explored. It is found that the reactivity of epoxides and aziridines are similar, and insertion of CO2 proceeds through a concerted mechanism. The substitutions of methyl and phenyl does not change the reaction mechanism, but the transition state for the substitution on the attacking position becomes loose with a lower free energy barrier. The substitutions of methyl and phenyl decrease the free energy barrier, with phenyl substitution having a greater affect. The results also show that the free energy barriers for the insertions of CO2 into aziridines are ~10kcalmol−1 lower than the corresponding reactions of CO2 with epoxides.

scholarly journals Ab Initio Study of Geminal Steric Hindrance Effects on the Stability of Conformations of Cyclohexane Derivatives

2005 ◽  
Vol 2005 (8) ◽  
pp. 508-515 ◽  
Author(s):  
Davood Nori-Shargh ◽  
Mostafa Mohamadpour Amini ◽  
Maryam Jafari ◽  
Farzad Deyhimi ◽  
Saeed Jameh-Bozorghi
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Energy Barrier ◽  
Density Functional ◽  
Energy Difference ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Conformational Properties ◽  
The Stability ◽  
Twist Boat

Ab initio and density functional theory methods (HF/3-21G*//HF/3-21G*, MP2/3-21G*//HF/3-21G*, B3LYP/3-21G*//HF/3-21G*, B3LYP/LANL2DZ*//HF/LANL2DZ*, MP2/LANL2DZ*//HF/LANL2DZ* and HF/LANL2DZ*//HF/LANL2DZ*) used to investigate the conformational properties of cyclohexane, 1,1-dimethylcyclohexane, 1,1-di-tert-butylcyclohexane, 1,1-bis(trimethylsilanyl)cyclohexane, 1,1-bis(trimethylgermanyl)cyclohexane and 1,1-bis(trimethylstannyl)cyclohex ane showed that the energy difference between the chair and twist-boat conformations and also the ring flipping energy barrier decreases from cyclohexane, 1,1-dimethylcyclohexane to 1,1-di-tert-butylcyclohexane, and increases from 1,1-bis(trimethylsilanyl)cyclohexane, 1,1-bis(trimethylgermanyl)cyclohexane to 1,1-bis(trimethylstannyl)cyclohexane.

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