Structural effects chemical reactivity

Within the context of this book the quantitative relationships between structure and chemical reactivity are very informative. One of the early postulates of Ingold and his school in the 1930s (review see Ingold, 1969, p. 78) was that the electronic effects of substituents are composed of two main parts a field/inductive component and a mesomeric component. Hammett s work indicated clearly from the beginning that his substituent constants am and crp reflect Ingold s postulate in numerical terms. In particular, many observations indicated that the /7-substituent constant ap is the sum of a field/inductive component 0 and a resonance (mesomeric) component (Jr. 

Structural- based Chemical reactivity of parent molecule or biotransformation to reactive metabolite Toxicophore Eliminate or reduce effect Reject... 

State [5] of the latter reaction. Reaction (48) might be believed to model properly the effect of the oo-bromo substituent on the nucleophilicity of the COj group. Unfortunately, even in this case the model does not work properly. In fact, the effect on the nucleophilicity is not only related to the effect of the bromine (relative to hydrogen) on the chemical potential of the initial state, but also on that of the transition state. Now it is clear that the situation met when the CO 2 nucleophile reacts with an external electrophile bears no relation to that met in the intramolecular reaction, where the bromine acts as a substituent in the initial state, but is the leaving group in the transition state. In other words, the useful distinction between a reacting and a non-reacting part of the molecule, on which many discussions of structural effects on reactivity... 

Shevchenko, S. M., T. J. Elder, S. G. Semenov, andM. Ya.Zarubin. 1995. Conformational effects on the electronic structure and chemical reactivity of lignin model p-quinone methides and benzyl cations. Res. Chem. Inter. 21(3-5) 413 23. 

Farombi, E.O. and Burton, G. Antioxidant activity of palm oil carotens in organic solution-effect of structural and chemical reactivity. Food Chemistry, 64(3), 315-321. 1999. 

Both the language of valence bond theory and resonance and that of molecular orbital theory are used in the discussion of structural effects on reactivity. Our intention is to illustrate the use of both typesr of interpretation, with the goal of facilitating the student s ability to understand and apply both of these viewpoints of structure. Nearly all reaction types and concepts are illustrated by specific examples from the chemical literature. Such examples, of course, cannot provide breadth of coverage, and those that are cited have been selected merely to illustrate the mechanism or interpretation. Such illustrations are not meant to suggest any... 

The concept of a structure-reactivity relationship implies that changes in structure should be quantitatively reflected in some measurable reactivity parameters associated with the molecule. For metal complexes, the capacity of the ligand structure to influence chemical properties is measurable in terms of reactivity parameters such as stability constants, rates of ligand dissociation, and reduction potentials. The influence of structure on chemical reactivity can often be rationalized in terms of steric and electronic components. MM calculations can be used to quantify the steric components present in the system. For metal complexes with series of ligands in which electronic effects are relatively constant (same number and type of donor atoms), reactivity differences can be attributed primarily to steric effects. In such cases, MM calculations have been used to obtain correlations between structure and reactivity. 

Huang Q, Li L, Fu X. 2007. Ultrasound effects on the structure and chemical reactivity of Corn starch granules. Starch/Starke 59 371-378. 

Hassel shared the 1969 Nobel Prize in chemistry with Sir Derek Barton of Imperial College (London) Barton demonstrated how Hassel s structural results could be extended to an analysis of conformational effects on chemical reactivity... 

Gronowitz et al. have discussed the effects of substituents on chemical reactivity and on ultraviolet (XJV), infrared (IR), and nuclear magnetic resonance (NMR) spectra in terms of simple resonance theory,They assume resonance structures (1-5) to contribute to a —I—M (Ingold s terminology) 2-substituted thiophene, resonance forms (6-10) to the structure of a drI-fM 2-substituted thiophene, forms (11-16) to a —I—M 3-substituted thiophene, and forms (17-22) to a I -M 3-substituted thiophene. 

Besides the electrostatic potential effect on reactivity, functionalized polyelectrolytes have a variety of interesting features worthy of study. If a polyelectrolyte is covalently modified with highly hydrophobic functional groups, it provides an unusual opportunity to study the chemical reactions of normally otherwise water insoluble functional groups in aqueous solution. Furthermore, a structural organization via hydrophobic interactions may occur in aqueous solution [25 — 31], which is of general scientific importance and is worth studying for its own sake. 

Brockway, L.O. The Structures of the Fluorochloromethanes and the Effect of Bond Type on Chemical Reactivity J. Phys. Chem. 1937, 41, 185-195. 

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