Substituent Effects on Menshutkin-Type Reactions in the Gas Phase and Solutions: Theoretical Approach from the Orbital Interaction View

2013 ◽  
Vol 9 (9) ◽  
pp. 4035-4045 ◽  
Author(s):  
Lizhi Jiang ◽  
Yuuichi Orimoto ◽  
Yuriko Aoki
Keyword(s):  
Gas Phase ◽  
Theoretical Approach ◽  
Substituent Effects ◽  
Orbital Interaction

Computational study of substituent effects on gas-phase stabilities of Meisenheimer complexes

2015 ◽  
Vol 93 (12) ◽  
pp. 1327-1334 ◽  
Author(s):  
Kazuhide Nakata ◽  
Mizue Fujio ◽  
Hans-Ullrich Siehl ◽  
Yuho Tsuno
Keyword(s):  
Gas Phase ◽  
Narrow Range ◽  
Computational Study ◽  
Substituent Effects ◽  
Orbital Interaction ◽  
Conjugation System ◽  
Isodesmic Reactions ◽  
Meisenheimer Complexes ◽  
Stabilization Energies ◽  
Respective Species

The total stabilization energies (TSEs) and anion stabilization energies (ASEs) of ring-substituted (X-) Meisenheimer complexes featuring two NO2 groups in the ring were determined using appropriate isodesmic reactions. The structures and energies of respective species were calculated at the B3LYP/6–311+G(2d,p) level of theory. Ten series of substituent effects were examined by varying substituent Y, which is connected to the sp3 carbon of the ring. The substituent effects were successfully analyzed using an extended Yukawa–Tsuno equation, [Formula: see text]. The r− values for the TSEs were identical to those for the ASEs, whereas the s values for the TSEs were significantly different from those for the ASEs. This shows that the effect of neutral species contributes to the s values of the TSEs. The r− and s values for the ASEs of all Meisenheimer complexes were distributed in a narrow range because substituent Y was insulated from the π-conjugation system. The r− values were large and the s values were small. This shows that the r− and s values were independent of each other and that the extended three-term Yukawa–Tsuno equation was intrinsic for substituent-effect analyses of anions. Although the variation was not substantial, the change in the r− values was clearly explained by the orbital interaction between substituent Y and the π-conjugation system. The r− values exhibited a good correlation with the bond lengths between the ring and the 4-NO2 group among all Meisenheimer complexes and benzylic anions. These facts provide a physical meaning: the r− value is a parameter that reveals the degree of the additional π interactions between the electron-withdrawing substituents and the π-conjugation systems of the ring.

Theoretical studies of SN2 transition states. Substituent effects

1982 ◽  
Vol 60 (11) ◽  
pp. 1291-1294 ◽  
Author(s):  
Saul Wolfe ◽  
David John Mitchell ◽  
H. Bernhard Schlegel
Keyword(s):  
Gas Phase ◽  
Transition States ◽  
Substituent Effects ◽  
Orbital Interaction ◽  
Frontier Orbital ◽  
Orbital Interactions ◽  
Pyramidal Inversion ◽  
New Type ◽  
Constraint Effects ◽  
And Inversion

Similar substituent and angular constraint effects are noted for pyramidal inversion at tricoordinate nitrogen and inversion at a carbon centre undergoing an SN2 displacement reaction. The former process has been analyzed successfully by a quantitative PMO analysis which focuses on the frontier orbital interactions between X and NH2 in the planar and pyramidal structures of X—NH2 molecules having X = F, CH3, CHO. Based on total energy calculations at the 6-311G*//4-31G level, the effects of X upon the rates of the gas phase SN2 reactions F− + XCH2F → XCH2F + F− are found to be [Formula: see text]. Taking the treatment of nitrogen inversion as a precedent, the origin of this trend has been examined by a quantitative PMO analysis which focuses on the frontier orbital interactions between X and CH2F2− in the transition states, and between X and CH2F in the reactants. This has revealed that the rate enhancement associated with an α-carbonyl substituent in these SN2 reactions can be related to the presence of a stabilizing orbital interaction of a new type in the transition state, coupled to an exceptionally low destabilizing orbital interaction.

Theoretical insight into the substituent effects on the antioxidant properties of 8-hydroxyquinoline derivatives in gas phase and in polar solvents

2018 ◽  
Vol 96 (5) ◽  
pp. 453-458
Author(s):  
Anes El-Hadj Saïd ◽  
Sidi Mohamed Mekelleche ◽  
Taki-Eddine Ahmed Ardjani
Keyword(s):  
Electron Transfer ◽  
Gas Phase ◽  
Antioxidant Properties ◽  
Substituent Effects ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Antioxidant Power ◽  
Theoretical Insight ◽  
Insight Into

The objective of this work is to perform a theoretical analysis of the antioxidant properties of a series of 8-hydroxyquinolines (8-HQs) to rationalize the available experimental results and to design new potent 8-HQ derivatives. The study was carried out in gas phase and in methanol at the DFT/B3LYP/ 6-311++G(d,p) computational level. The formation of stable ArO• radicals is discussed on the basis of different mechanisms, namely, hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and single proton loss electron transfer (SPLET). The obtained results show that the HAT mechanism is, thermodynamically, more favoured in gas phase, whereas the SPLET pathway is more favoured in polar solvents. The calculated thermochemical descriptors allow classification of the antioxidant power of the studied compounds.

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