Showing papers in "Advances in Physical Organic Chemistry in 1965"
TL;DR: In this article, molecular refractivity and polarizability of a particle is defined as the dipole moment induced by an electric field of unit intensity, and the principal polarizabilities of molecules can be analyzed in terms of anisotropic bond polarisation.
Abstract: Publisher Summary This chapter discusses molecular refractivity and polarizability. Refractive indices ( n ) of pure substances are more accurately measurable than any other optical properties. The refractive index of a substance varies with its physical state, temperature t , and wave-length λ of the light by which n is observed. The first two of these effects are attributed to the density d . The specific refraction r of a substance multiplied by the molecular weight is referred as molecular refraction. Polarizability of a particle is defined as the dipole moment induced by an electric field of unit intensity. The polarizabilities of monatomic ions and molecules are generally independent of field direction. The principal polarizabilities of molecules can be analyzed in terms of anisotropic bond polarizabilities. Polarizabilities are also responsible for the birefringence, which appears whenever the orientations of anisotropic molecules in an assemblage are derandomized or changed by any disturbing force.
344 citations
TL;DR: In this paper, the authors describe exchange reactions that deal with simple oxygen-containing organic molecules, such as alcohols, phenols, ketones, aldehydes, and carboxylic acids and their derivatives.
Abstract: Publisher Summary Isotope exchange reactions are reversible chemical processes in which two isotopes C and C* of the same element exchange places. No net chemical change takes place in these reactions, but only interchange of the isotopic label occurs. The large majority of exchange reactions studied are those between organic compounds and water. These reactions significantly provide a great deal of information on the mechanisms of the reaction of organic compounds. The isotopic exchange of oxygen in organic compounds involves the use of O 18 . The isotopic exchange of O 18 with organic compounds is important as a control in tracer studies, particularly in the systems of biological interest where water plays a prominent role. This chapter describes exchange reactions that deal with simple oxygen-containing organic molecules, such as alcohols, phenols, ketones, aldehydes, and carboxylic acids and their derivatives. It examines many organic derivatives of inorganic oxyacids, such as esters of phosphoric and sulphuric acids, for oxygen exchange with water. Few exchanges not involving water, such as the exchange of O 18 between organic compounds and alumina and other metal oxides, are also presented.
82 citations
TL;DR: In this article, the authors reviewed the information obtained about organic molecules from the temperature dependence of their nuclear magnetic resonance (NMR) spectra, including chemical shifts, nuclear spin-spin coupling constants via electrons, and nuclear relaxation times.
Abstract: Publisher Summary This chapter reviews the information obtained about organic molecules from the temperature dependence of their nuclear magnetic resonance (NMR) spectra. The parameters obtained from the study of NMR spectra include chemical shifts, nuclear spin–spin coupling constants via electrons, and nuclear relaxation times. The chapter also describes the connection between reaction velocities and NMR spectra. NMR methods can be applied to study all atoms that make up organic molecules, such as H 1 , H 2 , H 3 , and F 19 . Many of these nuclei are present in low natural abundance and some have, apart from a nuclear magnetic moment, a nuclear electric quadrupole moment. The nuclei of chlorine, bromine, and iodine occur in good natural abundance with a favorable nuclear magnetic moment, but they are less popular, because the signals are broad owing to the effects of nuclear electric quadrupole moments. The electric-field gradients near a halogen nucleus are invariably large in organic molecules, because they occur at the periphery of the molecule in a univalent state, leading to short relaxation times and consequent broad signals.
32 citations
TL;DR: In this article, the effect of substitution in a parent molecule upon the rate of a given reaction can be effectively studied without the complications arising from the co-operative effects of the solvent, as can occur in reactions in solution.
Abstract: Publisher Summary Gas phase offers significant advantages for the investigation of substituent effects on the reactivity of organic molecules. Gas-phase studies can also provide insights about the problem of salvation. In the gas-phase, it is possible to investigate the behavior of a single molecule, uninfluenced by the presence of the remainder of the system. The effect of substitution in a parent molecule upon the rate of a given reaction can thus be effectively studied without the complications arising from the co-operative effects of the solvent, as can occur in reactions in solution. This chapter describes the several investigations of homogeneous, molecular gas-phase elimination reactions. The reactions considered are essentially homogeneous and unimolecular. Three types of homogeneous mechanisms are considered that include radical nonchain, radical chain, and unimolecular mechanisms. The first two of these are multistep processes, having a common initial step; the homolytic splitting of the C–X bond. However, the third type of mechanism is one-step unimolecular decomposition, proceeding through a four-centered transition state.
14 citations