Advances in Physical Organic Chemistry 

About: Advances in Physical Organic Chemistry is an academic journal published by Elsevier BV. The journal publishes majorly in the area(s): Catalysis & Nucleophile. It has an ISSN identifier of 0065-3160. Over the lifetime, 205 publications have been published receiving 13069 citations. The journal is also known as: Physical organic chemistry.

Acid-Base Properties of Electronically Excited States of Organic Molecules

Abstract: Publisher Summary This chapter discusses acid–base properties of electronically excited states of organic molecules. Excited state pK-values are most easily accessible through the use of the Forster cycle. To perform this calculation for a particular molecule, it is necessary to know the ground state equilibrium constant for the reaction in question and to have some measure of the energy difference between the lowest vibrational level of the ground and the excited state in both the B and BH + forms. The effects of solvation on 0–0 energies are discussed. The changes in molecular fluorescence with acidity give information about the protolytic behavior of the excited singlet state of a compound. Two techniques, phase and pulse fluorometry, are used for the direct measurement of fluorescence decay rates. The excited state acid-base behavior of molecules has direct implications in the field of analytical fluorimetry and phosphorimetry.

Effective Molarities for Intramolecular Reactions

Abstract: Publisher Summary The first step toward unravelling the mechanism of an enzyme-catalyzed reaction is to specify the mechanisms available for the reaction concerned. Many of these reactions are not observed when the relevant groups are allowed to come together in bimolecular processes in aqueous solution. For mechanistic work involving intermolecular reactions, it is necessary to use activated substrates. An attractive alternative is to study intramolecular reactions. These are generally faster than the corresponding intermolecular processes. Thus, groups like carboxyl and imidazole are involved at the active sites of many enzymes hydrolyzing aliphatic esters and amides. Therefore, mechanistic studies of intramolecular reactions play an important part in elucidating the chemistry of the groups involved in enzyme catalysis and in defining the mechanisms available for particular reactions.

Organic Reactivity in Aqueous Micelles and Similar Assemblies

Abstract: Publisher Summary This chapter discusses thermal reactions in aqueous colloidal systems. It aims is to analyze the reactions from a mechanistic point of view, and therefore discussion is focused on organic reactions in aqueous micelles. The structure of micelles or other colloidal droplets is considered only to the extent needed to understand reactivity. A key feature of micelles and similar colloidal aggregates is that they can incorporate solutes. For example an ionic micelle can bind a non-ionic solute and also, by virtue of its charge, attract counterions. It may affect reaction rates and equilibria by bringing reactants together or keeping them apart, but because the micelle can exert a medium effect it is necessary to separate the “medium” and “concentration” effects of the micelle. It reviews that the overall subject of reaction in submicroscopic aggregates has expanded so rapidly and in so many different directions that interest on specific areas has to be focused. The general principles, which govern the effects of normal, aqueous, micelles on reaction rates and equilibria are considered and some specific reactions and the relation of micellar effects to mechanism are discussed.

Hydrogen Bonding and Chemical Reactivity

Abstract: Publisher Summary This chapter discusses the hydrogen bonding, which has been recognized as the single most important intermolecular interaction, The chapter presents the hypothesis that there are three kinds of hydrogen bond: weak, strong, and very strong. These are determined by the shape of the potential energy well and the respective positions of hydrogen and deuterium within the well, which can be used to provide information about the well that applies in a particular example. The role of hydrogen bonding in catalysis has been discussed, although mainly in terms of the salicylate ion as a leaving group. With its strong intramolecular hydrogen bond playing an essential part in the reaction mechanism, it seems likely that this will herald other systems where the role of a strong hydrogen bond may serve as the key step in a catalytic process.

Calculation of Molecular Structure and Energy by Force-Field Methods

Abstract: Publisher Summary This chapter discusses the calculation approaches to determine molecular structure and energy by force-field methods. These include the ab initio method, the force-field method, mechanical model, and energy minimization schemes. Methods for determining the internal energy of an organic molecule traditionally depend on heats of combustion. Because calculations of the force-field variety have become so accurate and efficient, many studies using such calculations to attack problems in molecular structure have been and are currently being carried out. These studies give, as a minimum, the bond lengths, bond angles, and torsional angles of the molecules examined, in addition to information concerning energy. The force-field method offers a rapid, convenient and reliable method for the determination of molecular structures and energies. While there are limitations to the method, as there are with each of the experimental methods, the usefulness of this technique is generally appreciated.