Oxygen Isotope Effect Research Articles

Phase equilibrium isotope effects in molecular solids and liquids. Vapor pressures of the isotopic carbon dioxide molecules

The vapor pressures of samples of CO2 enriched in C13 and O18 have been compared with normal CO2 over the temperature range 154−217°K. Over the entire temperature range the order of the vapor pressures is P13CO2 > P12CO2 > PC18O2. The results are explained by the small shift in the internal vibrations, which dominate the carbon isotope effect, and hindered rotation in the solid and liquid. While the isotope effect on melting is small for carbon substitution, it is found to be large for oxygen substitution. Hindered rotation is the major contribution to the oxygen isotope effect in the solid, while the hindered translation is the most important contribution to the oxygen isotope effect in the liquid. Model calculations of the logarithm of the reduced partition function ratios of the solid and liquid, ln(fc/fg), are made in an anharmonic version of the Stern−Van Hook−Wolfsberg cell model. These calculations give good agreement with the experimentally determined ln(fc/fg) values for the solid, liquid−vapor isotope fractionation measurements of Grootes, Mook, and Vogel, and lattice dynamic calculations.

Oxygen isotope effects in the synthetic reversible oxygen carrier systems: cobalt dihistidine-oxygen system

Oxygen isotope effects in the synthetic reversible oxygen carrier systems: cobalt dihistidine-oxygen system

Carbon and oxygen isotope effects in the decarbonylation of benzoylformic acid in concentrated sulphuric acid

Kinetic isotope effects for carbon and oxygen for the decarbonylation of benzoylformic acid in concentrated sulphuric acid have been measured, which together with measurements on isotopic exchange of oxygen with the solvent, support a mechanism in which C–O bond rupture occurs in the rate-determining step.

Absorption of Oxygen in Silicon in the Far Infrared

An absorption line of oxygen in silicon has been observed at 29.3 ${\mathrm{cm}}^{\ensuremath{-}1}$ at 1.8\ifmmode^\circ\else\textdegree\fi{}K. Assignment to oxygen has been confirmed by observation of the oxygen isotope effect. Effects of uniaxial stress on the line have been measured. Additional lines observed at 37.7, 43.5, and 48.9 ${\mathrm{cm}}^{\ensuremath{-}1}$ when the crystals are heated to 35\ifmmode^\circ\else\textdegree\fi{}K are assigned to a bending vibrational mode of ${\mathrm{Si}}_{2}$O.

Oxygen isotope effects in the oxidation of water by transition metal ions

The isotopic fractionation of oxygen in the oxidation of water by Co(III), Ni(IV), Cu(III) and Fe(phen)3+3 has been measured as well as that involved in the oxidation of water by hypochlorite and persulphate catalyzed by divalent cobalt, nickel and copper ions. In all reactions studied, the evolved oxygen is depleted in O18, fractionation factor ranging from 1.0022 to 1.0455. In the metal catalyzed reactions the same fractionation factor (O16/O18= 1.0293 ± 0.0006) was found, independent of the oxidant or the metal ion catalyst. The mechanisms of oxidation of water are discussed in terms of the isotopic fractionation data.

Oxygen isotope effects by a noncompetitive technique: The transition-state carbonyl stretching frequency in ester cleavage

Oxygen isotope effects by a noncompetitive technique: The transition-state carbonyl stretching frequency in ester cleavage

Kinetic oxygen and hydrogen isotope effects in the hydroxide ion catalized reaction of 2,4-dinitrophenyl phenyl ether with piperidine in aqueous dioxane

Kinetic oxygen and hydrogen isotope effects in the hydroxide ion catalized reaction of 2,4-dinitrophenyl phenyl ether with piperidine in aqueous dioxane

Applications of Oxygen Isotopes in Chemical Studies

The choice of the general subject of this article requires no apology, but the choice of the specific material to fit to the space allotted does. The limita­ tions and research interests of the reviewer were a governing factor in mak­ ing the selection, but also the consideration entered that the effects of the major omissions are tempered by other recent reviews in which much of the material omitted is discussed. Thus the important work in geochemistry involving oxygen isotopes is discussed in excellent reviews by Dole (I), and more recently by Craig & Boata (2). The work on heterogenous systems is discussed more completely in the article by Dole. It is hoped in this connec­ tion that a general article on the application of isotopes in the study of heterogeneous catalysis, induding work with oxygen isotopes, will be forth­ coming. In the subjects chosen for review, an effort has been made to be com­ plete ; and earlier literature as well as the more recent has been referred to. When work which is within the scope of the subject matter is not cited, it is because of oversight or because the work is dealt with in a more general article by the same author. The present article stresses the application of oxygen isotopes to the study of chemical phenomena in homogeneous solution. Much of the work exploiting oxygen isotope effects has been done for such systems. For reac­ tions of oxygen-containing substances in an oxide-labile solvent such as water, isotope studies can answer important questions which no other method can answer as directly; and they have been of great help in defining the nature of the solvent and of the substances dissolved in it, and in exposing the mechanisms of reactions in solution.

Oxygen Isotope Effects at Anodes

Oxygen Isotope Effects at Anodes

Use of Oxygen Isotope Effects in Study of Hydration of Ions

Use of Oxygen Isotope Effects in Study of Hydration of Ions

Oxygen and Nitrogen Isotope Effects in the Decomposition of Ammonium Nitrate

The isotopic composition of the products of the controlled thermal decomposition of ammonium nitrate has been studied. It has been found that small amounts of water are necessary to initiate the decomposition of ammonium nitrate. N15H4NO3 has been found to yield exclusively the isomer N15N14O. Some inferences are drawn from this observation regarding the mechanism of the reaction. Oxygen and nitrogen isotope effects accompanying the decomposition have been studied with material of ``natural'' isotopic composition. Satisfactory agreement is found between the experimental results and theoretical calculations. A method for the isotopic analysis of nitrates for O18 is outlined.