Similarity Approach to Chemical Reactivity. Substituent Effect in Pericyclic Reactions

1993 ◽  
Vol 58 (1) ◽  
pp. 11-23 ◽  
Author(s):  
Robert Ponec
Keyword(s):  
Substituent Effect ◽  
Chemical Reactivity ◽  
Theoretical Data ◽  
Systematic Investigation ◽  
Pericyclic Reactions ◽  
Basic Features

The recently introduced similarity approach to chemical reactivity was applied to the systematic investigation of the substituent effect on pericyclic reactivity. The agreement of the resulting predictions with available experimental or theoretical data confirms that the basic features of the substituent effect are correctly reproduced by the model.

Substituent effect on chemical reactivity of cephalosporins studied by kinetic and 13C NMR(1)

2010 ◽  
Vol 92 (1) ◽  
pp. 81-82 ◽  
Author(s):  
A. Schanck ◽  
B. Coene ◽  
J. M. Dereppe ◽  
M. van Meerssche
Keyword(s):  
13C Nmr ◽  
Substituent Effect ◽  
Chemical Reactivity

Similarity approach to chemical reactivity. Torquoselectivity in pericyclic reactions

1996 ◽  
Vol 20 (2) ◽  
pp. 301-310 ◽  
Author(s):  
Robert Ponec ◽  
Gleb Yuzhakov ◽  
Jaroslav Pecka
Keyword(s):  
Chemical Reactivity ◽  
Pericyclic Reactions

Topological aspects of chemical reactivity. On the possible use of similarity index in characterizing the transition state structure in concerted pericyclic reactions

1987 ◽  
Vol 52 (6) ◽  
pp. 1375-1385
Author(s):  
Robert Ponec
Keyword(s):  
Transition State ◽  
Chemical Reactivity ◽  
Transition States ◽  
Similarity Index ◽  
Pericyclic Reactions ◽  
State Structure ◽  
Transition State Structure ◽  
Topological Similarity

The use of the topological similarity index as a simple means for classification and characterization of the structure of the transition states in concerted pericyclic reactions is discussed. The suggested formulation makes it possible to bring a quantitative aspects into the empirical Dewar's classification of transition states in terms of aromaticity and/or antiaromaticity.

Topological aspects of chemical reactivity. A simple method for estimating the activation energies in pericyclic reactions

1986 ◽  
Vol 51 (1) ◽  
pp. 175-187
Author(s):  
Robert Ponec
Keyword(s):  
Quantum Chemical ◽  
Chemical Reactivity ◽  
Activation Energies ◽  
Topological Model ◽  
Pericyclic Reactions ◽  
Simple Method ◽  
Proposed Model ◽  
Designed Synthesis

A simple topological model allowing to estimate the activation energies in thermally initiated pericyclic reactions is proposed. The formalism of the model is closely connected with the recently formulated overlap determinant method. Due to its simplicity the proposed model is especially convenient for the semiquantitative estimate of the reactivity, e.g. in computer designed synthesis where even the simplest quantum chemical procedures are still too time consuming.

scholarly journals A Systems-Pharmacology Analysis of Herbal Medicines Used in Health Improvement Treatment: Predicting Potential New Drugs and Targets

2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Jianling Liu ◽  
Mengjie Pei ◽  
Chunli Zheng ◽  
Yan Li ◽  
Yonghua Wang ◽  
...  
Keyword(s):  
Chemical Reactivity ◽  
Herbal Medicines ◽  
Well Being ◽  
Energy System ◽  
Systematic Investigation ◽  
Mechanisms Of Action ◽  
New Drugs ◽  
Health Improvement ◽  
Systems Pharmacology ◽  
Physical Strength

For thousands of years, tonic herbs have been successfully used all around the world to improve health, energy, and vitality. However, their underlying mechanisms of action in molecular/systems levels are still a mystery. In this work, two sets of tonic herbs, so called Qi-enriching herbs (QEH) and Blood-tonifying herbs (BTH) in TCM, were selected to elucidate why they can restore proper balance and harmony inside body, organ and energy system. Firstly, a pattern recognition model based on artificial neural network and discriminant analysis for assessing the molecular difference between QEH and BTH was developed. It is indicated that QEH compounds have high lipophilicity while BTH compounds possess high chemical reactivity. Secondly, a systematic investigation integrating ADME (absorption, distribution, metabolism, and excretion) prediction, target fishing and network analysis was performed and validated on these herbs to obtain the compound-target associations for reconstructing the biologically-meaningful networks. The results suggest QEH enhance physical strength, immune system and normal well-being, acting as adjuvant therapy for chronic disorders while BTH stimulate hematopoiesis function in body. As an emerging approach, the systems pharmacology model might facilitate to understand the mechanisms of action of the tonic herbs, which brings about new development for complementary and alternative medicine.

scholarly journals A Common Selection Rule for Organic Reactions in Terms of Signs of Direct and Indirect Interorbital Interactions

2009 ◽  
Vol 64 (1-2) ◽  
pp. 132-148 ◽  
Author(s):  
Viktorija Gineityte
Keyword(s):  
Power Series ◽  
Total Energy ◽  
Selection Rule ◽  
Chemical Reactivity ◽  
Organic Reactions ◽  
Chemical Bonds ◽  
Pericyclic Reactions ◽  
Order Energy ◽  
Phenyl Rings ◽  
Substituted Alkanes

The semilocalized approach to chemical reactivity suggested recently is overviewed with respect to both theory and applications. The principal attention is paid to formulation of a common selection rule for organic reactions and to demonstration of its validity to various heterolytic (i. e. nucleophilic and electrophilic) and pericyclic processes. The total energy of the whole reacting system (E) is represented in this approach in the form of power series with respect to all interfragmental interactions (fragments coincide with individual chemical bonds, phenyl rings, etc.). For any reaction, a certain decisive k-th-order energy correction E(k) may be revealed, the sign of which depends on the actual way of the process. The allowed and forbidden reactions are then defined as those described by negative (stabilizing) and positive (destabilizing) corrections E(k), respectively. The condition which ensures the negative sign of E(k) resolves itself into a universal requirement of coinciding signs of the principal direct and indirect interactions of basis orbitals localized on separate fragments (e. g. bond orbitals). This result forms the basis for the above-mentioned selection rule. Allowed (forbidden) ways of heterolytic reactions are exemplified by the back (frontal) attack of a nucleophile upon a substituted alkane in the SN2 process, the meta (ortho, para) attacks of electrophile upon the pyridine molecule, the addition of electrophile to the Cβ (Cα ) atom of a donor-containing derivative of ethene (D-CαH=Cβ H2), the trans (cis)-β -elimination processes of substituted alkanes, etc. Application of the same rule to pericyclic reactions is demonstrated to yield predictions coinciding with those of other approaches including the famous Woodward-Hoffmann rule.

Geodesic Formulation of the Least Motion Principle in Chemical Reactivity

1992 ◽  
Vol 57 (2) ◽  
pp. 232-240 ◽  
Author(s):  
Martin Strnad ◽  
Robert Ponec
Keyword(s):  
Mathematical Model ◽  
Hilbert Space ◽  
Structural Changes ◽  
Chemical Reactivity ◽  
The State ◽  
Pericyclic Reactions ◽  
Electron States ◽  
Intuitive Criterion

In this study an attempt is presented at the quantitative formulation of the old intuitive criterion for the characterization of chemical reactivity known as the principle of the least motion. The proposed formulation originates from the abstract mathematical model, within the framework of which the criterion of minimal structural changes is realized by the requirement of minimal changes of the state vectors in the Hilbert space of electron states. The presented approach is demonstrated on the practical example of pericyclic reactions for which its results correctly reproduce the conclusions of Woodward-Hoffmann rules.

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