Hydrogen Isotope Exchange Reactions Research Articles

Effect of the PPh3 ligand on hydrogen isotope exchange of ?-aromatic ligand in arenechromium dicarbonyl triphenylphosphines

1. When the CO ligand in ArCr(CO)3 complexes is replaced by the PPh3 ligand the rate of the hydrogen isotope exchange reaction with CF3COOD increases by more than three orders of magnitude. 2. In protophilic hydrogen isotope exchange reactions with C2H5ONa in C2H5OD the PPh3 ligand retards the hydrogen exchange in the π-benzene ring in C6H6Cr(CO)2PPh3 by approximately 20 times when compared with C6H6Cr(CO)3.

Kinetics of hydrogen isotope exchange reactions. Part XXII. Reactivity comparisons for a series of aromatic substrates towards radiolytically generated tritium atoms in aqueous solution

The relative reactivities of a series of aromatic compounds towards tritium atoms, generated by β-radiolysis, have been determined in degassed aqueous solution by a competition method, involving copper(II) ions as common competitor in the radiation-induced aromatic hydrogen exchange. Under these conditions, steps subsequent to the formation of the cyclohexadienyl radical are not kinetically significant. It is shown that comparable doses of γ-irradiation induce an equivalent extent of exchange. From the effect of low concentrations of copper(II) ions on the β-radiation-induced exchange rate it is concluded, that the reversion of the intermediate cyclohexadienyl radical to aromatic compound normally involves an oxidation step [reaction with residual oxygen or copper(II)], and that bimolecular radical–radical reactions are unimportant. The rates of tritium atom attack relative to benzene are: mesitylene, 8·5; toluene, 2·2; anisole, 2·7; fluorobenzene, 1·0; chlorobenzene, 1·1; bromobenzene, 1·1; benzonitrile, 0·9; trifluoromethylbenzene, 0·35; and t-butylbenzene, ca. 2–4. Because of an intramolecular kinetic isotope effect, the rate of radiation-induced tritium uptake by mesitylene is ca. 1·5 ± 0·2 times larger than that by [2,4,6-2H3]mesitylene. The extinction coefficients at the u.v. absorption maxima for these substrates in aqueous solution have been redetermined. The solubility of t-butylbenzene in water at 25° was found to be (1·9 ± 0·1)× 10–2 g dm–3. The rate constant for the reaction of hydrogen (tritium) atoms with iodide ion is ca. 5·5 × 107 dm3 s–1 mol–1.

Kinetics of hydrogen isotope exchange reactions. Part XXIII. Isomer distributions in the radiation-induced tritiation of benzene derivatives in aqueous solution

The isomer distribution of aromatic tritiation induced by γ-irradiation of solutions of aromatic compounds (anisole, toluene, chlorobenzene, and fluorobenzene) in tritiated water was examined by nitration of the reaction product, separation, and tritium assay of the isomeric mononitration products. In toluene and anisole, ca. 70% of tritium atom attack occurs at ortho-positions; in the two halogenobenzenes the attack appears to be approximately statistical.

Echanges isotopiques d'hydrogène T‐H, T‐D, D‐H et H‐D de la diazoacétone et du diazoacétaldéhyde: Vitesse de protonation et effets isotopiques. Communication préliminaire

AbstractThe velocities of four acid‐catalysed hydrogen isotope exchange reactions between diazoacetone (1) and water (T → H, T → D, D → H, and H → D) and of three exchange reactions between diazoacetaldehyde (2) and water (T → H, T → D, and H → D) have been measured. The exchange D → H of 1 was found to be submit to general acid catalysis (αB = 0.6). The rates of protonation of primary and secondary diazocarbonyl compounds of similar structure were found to be quite similar, in spite of difference in mecanism (A‐2 and A‐SE2, respectively).

Kinetics of hydrogen isotope exchange reactions. Part XXI. Heterolytic tritium exchange between resorcinol and water in the homogeneous liquid phase

The rate of tritium loss from ring-labelled resorcinol to the solvent has been measured for aqueous solutions of resorcinol, containing either added hydrochloric acid or sodium hydroxide, at 13·5 °C. The experimental technique involved isotopic assays of samples of water vapour in equilibrium with the solution, i.e., without disturbance of the acid–base equilibria or concentrations of solutes.

Kinetics of hydrogen isotope exchange reactions. Part XVIII. Aliphatic exchange induced by β-radiation on aqueous solutions of alcohols

A pcH-independent β-radiation-induced hydrogen exchange reaction has been observed for aqueous solutions of t-butyl alcohol containing greater than 8 Ci/l of tritium as part of the solvent. Repeated gas-chromatographic separations of t-butyl alcohol isolated from these solutions lead to the conclusion that the tritiated species is t-butyl alcohol with tritium in the methyl groups. The amount of exchange is proportional to radiation dose, and increases with increasing concentration of substrate, apparently towards a limiting maximum rate.

Kinetics of hydrogen isotope exchange reactions. Part XIX. Effect of added solutes on aliphatic tritium exchange of t-butyl alcohol(2-methylpropan-2-ol) under the influence of β-radiation, and related experiments

The effect of added solutes (AgClO4, CdSO4, CuSO4, NiSO4, and H2O2) on the tritium exchange in the methyl groups of t-butyl alcohol is to decrease the exchange rate very sharply, the silver salt having the most pronounced influence. The inhibitors do not totally suppress the exchange. The results suggest that there are two exchange routes the major one of which is susceptible to inhibition by electron scavengers while the minor one is not. As a working hypothesis it is suggested that the major exchange route involves reaction between the hydrated electron and t-butyl alcohol. This results in the formation of a solvated electron containing one molecule of t-butyl alcohol in the cluster of solvent molecules in which the electron is trapped with consequent hydrogen exchange between the molecules of the cluster. The minor route is envisaged as the direct formation of this mixed solvent cluster by the action of radiation. The scavenger effects suggest that the second-order rate constant for the reaction between t-butyl alcohol and the hydrated electron is ca. 108 l mol–1 s–1. Since this reaction does not destroy the solvated electron, the high value deduced is not incompatible with the low rate constants obtained for the destruction of the hydrated electron by alcohols from pulse-radiolysis studies.

Kinetics of hydrogen isotope exchange reactions. Part XX. Aliphatic exchange induced by γ-radiation on aqueous solutions of t-butyl alcohol (2-methylpropan-2-ol)

Download options Please wait... Article information DOI https://doi.org/10.1039/J29700001808 Article type Paper Download Citation J. Chem. Soc. B, 1970, 1808-1811 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Kinetics of hydrogen isotope exchange reactions. Part XX. Aliphatic exchange induced by γ-radiation on aqueous solutions of t-butyl alcohol (2-methylpropan-2-ol) J. H. Rolston and V. Gold, J. Chem. Soc. B, 1970, 1808 DOI: 10.1039/J29700001808 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author J. H. Rolston V. Gold

Kinetics of hydrogen isotope exchange reactions. Part XVI. Aromatic exchange under the influence of β-radiation on aqueous solutions of mesitylene

An uncatalysed exchange reaction between water and mesitylene has been observed in homogeneous solutions containing ca. 4 curies of tritiated water per litre. The predominant reaction product is mesitylene labelled in the aromatic ring. The exchange rate depends on the second power of the tritium concentration, and the exchange is therefore attributed to the influence of the β-radiation emitted by the tritium in solution. On the basis of the dependence of the exchange rate on the concentration of mesitylene and of added cupric and nickel ions, the exchange is considered to be initiated by attack of tritium atoms on mesitylene, leading to a methyl-substituted cyclohexadienyl radical as an intermediate. The results are incompatible with attack on mesitylene by solvated electrons as the initiating step.

Kinetics of hydrogen isotope exchange reactions. Part XVII. Competition between mesitylene and benzene in aromatic exchange under the influence of β-radiation

The radiation-induced tritium uptake by mesitylene is inhibited by the addition of benzene. This inhibition is quantitatively accounted for by tritium exchange in benzene, which competes with mesitylene for the tritiating species. The total reactivity ratio mesitylene : benzene (referring to the sum of all reactions by which the tritiating species can be scavenged by these compounds) is 9; the exchange reactivity ratio (which applies only to the processes leading to tritiated mesitylene and benzene) is 8·5 ± 0·5. The enhancement of the reactivity by methyl substituents supports the formulation of the reaction mechanism in terms of radiolytically produced tritium atoms, and the agreement between the two estimates is shown to point to the relative unimportance of scavenging reactions by these aromatic molecules other than by a process which results in tritium exchange. On this basis the amount of tritium exchange in mesitylene is shown to agree with the yield of tritium atoms calculated from the known internal radiation dose to which the solutions are exposed, provided an isotope effect of ca. 10–20 (discriminating against the formation of tritium atoms relative to protium atoms) is assumed.

The kinetics of hydrogen isotope exchange reactions. Part XV. Acid-catalysed tritiation of mesitylene and correlation of exchange rates with Hammett's acidity function

Download options Please wait... Article information DOI https://doi.org/10.1039/J29690000950 Article type Paper Download Citation J. Chem. Soc. B, 1969, 950-956 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions The kinetics of hydrogen isotope exchange reactions. Part XV. Acid-catalysed tritiation of mesitylene and correlation of exchange rates with Hammett's acidity function J. R. Adsetts and V. Gold, J. Chem. Soc. B, 1969, 950 DOI: 10.1039/J29690000950 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author J. R. Adsetts V. Gold

Kinematic Model for Atom–Diatom Reactions

A simple model for atom–diatom reactions is completely analyzed. The model represents the molecule by two hard spheres nearly in contact and the atom by a third hard sphere. Energy and momentum transfers among the three particles are calculated for all values of molecular orientation and collision parameters. On the basis of the kinematic analysis and in terms of an activation parameter, probabilities are assigned to the various reactions which may occur. Using as parameters the bond length of H2 and the activation energy for H+H2, the model predicts (a) the energy dependence of the H+H2 cross section, in agreement with the complete classical analysis of Karplus et al.; (b) rate constants for hydrogen isotopic exchange reactions which agree with experiment when threshold effects do not dominate; and (c) the hot-atom behavior of the T+H2 and T+D2 systems in substantial agreement with both experiment and the complete classical analysis. Methods for extending the model are discussed.

Effect of the methyl group on the isotope exchange rate for hydrogen in the o-, m-, and p-positions in tricarbonyltoluene chromium in alkaline media

The hydrogen isotope exchange reaction of carbonyltoluene chromium in ethanol in the presence of a sodium alcoholate has been studied. The partial rate factors for the o-, m-, and p- positions in the aromatic ring in this system have been determined.

The kinetics of hydrogen isotope exchange reactions. Part XIV. Acid-catalysed tritium exchange and its relationship to the dehydration of t-butyl alcohol

The rate of hydrogen exchange between tritium-containing aqueous perchloric acid and the C–H bond of dissolved t-butyl alcohol has been measured at 25° as a function of acid concentration. The logarithm of the rate constant is a linear function of H0 with slope –1·35. On the assumption that exchange takes place by dehydration to isobutene followed by re-addition of labelled water, the results are used to obtain the rate constant for dehydration of t-butyl alcohol in 0·5M-perchloric acid. The value found agrees with one calculated by combining the previously determined rate constant for hydration of isobutene with the equilibrium constant for the hydration reaction evaluated from thermodynamic data. This agreement supports the view that the route via olefin is the most significant mechanism of hydrogen exchange of t-butyl alcohol in moderately dilute aqueous acid at 25°.

823. The kinetics of hydrogen isotope exchange reactions. Part XIII. Isotope effects in the acid-catalysed hydrogen exchange of 1,3,5-trimethoxybenzene

823. The kinetics of hydrogen isotope exchange reactions. Part XIII. Isotope effects in the acid-catalysed hydrogen exchange of 1,3,5-trimethoxybenzene

3d-orbital resonance in divalent sulphides—IV: Acidity of hydrogen atom adjacent to mercapto groups

The rates of base-catalysed hydrogen-isotope exchange reactions of various sulphides and their corresponding oxygen analogues have been measured in order to compare the relative acidifying effects of mercapto and alkoxy groups toward α-hydrogen atoms. Practically no exchange reaction was abserved in the oxygen compounds, whereas, with the sulphur compounds, the reaction readily takes place, the rate being increased several powers of ten by the substitution of one additional mercapto group. Furthermore, dramatic rate increase was observed when an open chain compound, orthothioformate was cyclized to the corresponding bicyclic compound. These observations are interpreted in terms of the 3d orbital resonance of the sulphur atom.

361. The kinetics of hydrogen isotope exchange reactions. Part XI. Tritium exchange between secondary alcohols and acidic media

of Nb oxide were identified: Nb-(O) (solid solution), NbO/sub x/ (tetragonal), Nb-O delta -form (hexagonal), gamma -Nb/sub 2/O/sub 5/ (monoclinic), and alpha -Nb/sub 2/O/sub 5/ (monoclinic) were formed by heating in air at either atmospheric or reduced pressure; while, NbO/sub z/ (tetragonal), NbO (cubic), and NbO/sub 2/ (tetragonal) were formed only in air at reduced pressure. The transformation relations between the oxides are made clear. At first, the oxidation of Nb occurs through penetration of O atoms into the metallic lattice of Nb. Then the structures of the oxides transform successively by rearrangement of Nb and the O atoms. The transformation delta and up to st r gamma can take place through a relatively small change in the atomic distribution, while the transformation gamma and up to st r alpha occurs through a remarkable rearrangement of both kinds of atoms, passlng two distlnct intermediate stages. The delta -form may be an oxide inferior to NbO/sub 2/. The tetragonal form NbO/sub 2/ has a super lattice derived from the rutile structure. (auth)

362. The kinetics of hydrogen isotope exchange reactions. Part XII. The behaviour of primary alcohols in acidic media

362. The kinetics of hydrogen isotope exchange reactions. Part XII. The behaviour of primary alcohols in acidic media

497. The kinetics of hydrogen isotope exchange reactions. Part X. The acid-catalysed detritiation of [o-3H]p-cresol in water and in deuterium oxide

The loss of tritium from STAo-H/sup 3/! p-cresol was studied kinetically in aqueous hydrochloric acid in the approximate concentration range 3.5 to 6.5N. The reaction velocity was found to have the same dependence on acidity as the previously investigated exchange of STAo-H/sup 2/!p-cresol. At the same acidity, detritiation is 2 to 3 times slower than deuteration. The detritiation cccurs 1.62 times faster in deuterium oxide than in protium oxide solutions of 4N hydrochloric acid. The velccity in mixtures of deuterium oxide and water follows the predictions of the Gross-Butler theory. The mechanism of aromatic hydrogen exchange is discussed. (auth)

196. The kinetics of hydrogen isotope exchange reactions. Part IX. The exchange between cobalt (III) ammines and water

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