Perturbation theory of substituent effect. Quantum chemical estimation of the Hammet ρ constants

1980 ◽  
Vol 45 (6) ◽  
pp. 1646-1654 ◽  
Author(s):  
Robert Ponec
Keyword(s):  
Perturbation Theory ◽  
Simple Model ◽  
Quantum Chemical ◽  
Substituent Effect ◽  
Reaction Constant ◽  
Chemical Analogue

Based upon a simple model describing the substituent effect only by a change in the Coulombic integral Δαμ, a relation is derived which can be viewed as a quantum chemical analogue of the Hammet equation. This relation and knowledge of the reaction constant ρ for a reaction on a skeleton chosen as a standard make it possible to predict theoretically the magnitude of the ρ constant for this reaction on an arbitrary conjugated skeleton provided that for the latter the Hammet equation holds.

Perturbation theory of substituent effect. Quantum chemical study of the positive bridging effect

1980 ◽  
Vol 45 (7) ◽  
pp. 2054-2062 ◽  
Author(s):  
Robert Ponec
Keyword(s):  
Perturbation Theory ◽  
Quantum Chemical ◽  
Substituent Effect ◽  
Quantum Chemical Study ◽  
Reaction Medium ◽  
Chemical Study ◽  
Hammett Equation ◽  
Solvation Effects ◽  
Chemical Analogue

Mechanism of the so-called positive bridging effect was studied on the basis of an equation which can be viewed as a quantum chemical analogue of the Hammett equation. From this study it follows that the effect is presumably due to solvation effects of the reaction medium.

Perturbation theory of substituent effect. Importance of the field effect in transmission of the substituent effect

1980 ◽  
Vol 45 (6) ◽  
pp. 1655-1661 ◽  
Author(s):  
Robert Ponec
Keyword(s):  
Perturbation Theory ◽  
Carboxylic Acids ◽  
Quantum Chemical ◽  
Substituent Effect ◽  
Field Effect ◽  
Adequate Description ◽  
Meta Position ◽  
Unsaturated Carboxylic Acids

Various quantum chemical approaches to the problem of transmission of the substituent effect were compared. It was shown that inclusion of the electronic repulsion (field effect) was necessary to give a true picture of differences in ρ constants for reactions of the cis and trans isomers of substituted unsaturated carboxylic acids; the same holds for an adequate description of transmission of the substituent effect from the meta position on a given skeleton.

Dihydronaphthalenone Carboxylates - Spectral Characteristics and Structure

1997 ◽  
Vol 52 (5) ◽  
pp. 457-461 ◽  
Author(s):  
Sn. Bakalova ◽  
A. Georgieva ◽  
P. Nikolov ◽  
E. Stanoeva
Keyword(s):  
Ir Spectra ◽  
Quantum Chemical Calculations ◽  
Electronic Spectra ◽  
Quantum Chemical ◽  
Substituent Effect ◽  
Methyl Esters ◽  
Spectral Characteristics ◽  
Absorption Bands ◽  
Tautomeric Forms ◽  
Luminescence Characteristics

Abstract The absorption and luminescence characteristics of a group of newly synthesized methyl esters of 2-alkyl (p-substituted-aryl) -aminomethylene-3,4-dihydro-1(2 H)-naphthalenone-4-carboxylic acids have been investigated. The studied compounds may exist in three tautomeric forms. On the basis of comparison of their electronic spectra to those of similar substances, the observed substituent effect on the position of the UV-VIS absorption bands, the IR spectra and the results of PPP-SCF-CI quantum-chemical calculations it is concluded that the keto tautomer predominates in solution.

Separation of the Enthalpic and Entropic Contributions to Substituent Effects for the Equilibrium Constants of Aromatic Acids

1975 ◽  
Vol 53 (23) ◽  
pp. 3622-3633 ◽  
Author(s):  
T. M. Krygowski ◽  
W. R. Fawcett
Keyword(s):  
Substituent Effect ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Point Of View ◽  
Aromatic Acids ◽  
Resonance Effects ◽  
Equation Analysis ◽  
Reaction Constant ◽  
Enthalpy And Entropy Changes ◽  
Substituent Constants

Separation of the substituent effect ρσ into entropie ρSσS and enthalpic ρHσH contributions is presented within the framework of the general Hammett equation. Analysis of the experimental data for aromatic acids shows that, in general, entropie effects are the major contribution to the total substituent effect, the entropic reaction constant being approximately equal to the normal Hammett ρ A comparison of the present results with those based on a separation of inductive and resonance effects shows that the entropie and inductive effects are directly related. On the other hand, strongly resonance interacting substituents were found to be enthalpy controlled. The substituent effect on enthalpy and entropy changes is discussed from a molecular point of view and related to inductive and resonance effects. A list of 16 enthalpic (σH) and entropie (σS) substituent constants are presented.

Solvatochromic and quantum chemical investigations of newly synthesized succinimides: substituent effect on intramolecular charge transfer

2013 ◽  
Vol 144 (10) ◽  
pp. 1525-1535 ◽  
Author(s):  
Nebojša Banjac ◽  
Nemanja Trišović ◽  
Željko Vitnik ◽  
Vesna Vitnik ◽  
Nataša Valentić ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Quantum Chemical ◽  
Substituent Effect ◽  
Intramolecular Charge Transfer

scholarly journals Hydrogenation of HOPG-supported Gold Nanoparticles: Features of Initial Stages

Crystals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 350
Author(s):  
Andrey K. Gatin ◽  
Maxim V. Grishin ◽  
Nadezhda V. Dokhlikova ◽  
Sergey Yu. Sarvadii ◽  
Boris R. Shub
Keyword(s):  
Experimental Data ◽  
Gold Nanoparticles ◽  
Simple Model ◽  
Quantum Chemical ◽  
Room Temperature ◽  
Pyrolytic Graphite ◽  
Highly Oriented Pyrolytic Graphite ◽  
Entire Surface ◽  
Supported Gold Nanoparticles ◽  
Supported Gold

The features of deuterium adsorption on the surface of gold nanoparticles deposited on highly oriented pyrolytic graphite (HOPG) were determined. The results showed that deuterium adsorption on gold nanoparticles takes place at room temperature. The results also showed that the filling of the nanoparticles’ surfaces with the adsorbate occurs from the graphite–gold interface until the entire surface is covered by deuterium. The results of quantum chemical simulations are used to explain the experimental data. A simple model of the observed effects is proposed.

Association ofN-(Pyridin-2-yl),N′-substituted Ureas with 2-Amino-1,8-naphthyridines and Benzoates: NMR and Quantum Chemical Studies of the Substituent Effect on Complexation

2013 ◽  
Vol 78 (15) ◽  
pp. 7582-7593 ◽  
Author(s):  
Borys Ośmiałowski ◽  
Karina Mroczyńska ◽  
Erkki Kolehmainen ◽  
Magdalena Kowalska ◽  
Arto Valkonen ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Substituent Effect ◽  
Chemical Studies ◽  
Quantum Chemical Studies

THE COOPERATIVITY BETWEEN HYDROGEN AND HALOGEN BONDS

2008 ◽  
Vol 07 (01) ◽  
pp. 13-35 ◽  
Author(s):  
TIMM LANKAU ◽  
YU-CHUNG WU ◽  
JIAN-WEI ZOU ◽  
CHIN-HUI YU
Keyword(s):  
Simple Model ◽  
Hydrogen Bonds ◽  
Quantum Chemical ◽  
Halogen Bond ◽  
Computational Method ◽  
Halogen Bonds ◽  
Reasonable Accuracy ◽  
Reference Cluster ◽  
Hybrid Functionals ◽  
Two Parameter

The cooperativity between hydrogen bonds and halogen bonds in X–HCN–Y ( X: C2H2, H2O, NH3, HCI, HCN, HF; Y: HF, BrF, Br2 is analyzed with MP2/6-311++G(d, p) and DFT/6-311++G(d, p) calculations using the B3LYP and mPW1PW91 hybrid functionals. The results from the quantum chemical calculations are typically clustered in groups according to the Y-ligand. By choosing the X–HCN–HF group as reference it is possible to describe the interaction between the hydrogen and the halogen bond with a two-parameter model. The value of the first parameter of the model describes the contribution of the X -ligand to the interbond cooperativity in the reference cluster. The second parameter of our model quantifies the changes in interbond cooperativity upon varying the Y -ligand. This simple model can be used to predict the cooperativity in X–HCN–Y trimers with reasonable accuracy and thereby to organize the results systematically. It is further shown that the conclusions drawn from this ordering scheme are independent from the computational method and thereby generally applicable.

Sign in / Sign up

Export Citation Format

Share Document