Hydrogen Isotope Exchange Reactions Research Articles

Hydrogen Isotope Exchange Reactions in an Atmospheric Pressure Discharge Utilizing Water as Carrier Gas

Allowing water/hydrogen or water/hydrogen/He gas mixture to flow through micro- hollow type of electrodes and applying 60 Hz AC power between the electrodes made it possible to sustain large area and atmospheric pressure discharge. The electrode assembly was constructed by sandwiching a dielectric spacer with two thin metal sheets and boring an array of micro holes through them. Another variation of the assembly was prepared by stacking thin metallic sheets so that the stack functions as an electrode through which the gas mixture flows for generating dielectric barrier discharge. A large volume of the gas mixture, while producing plasma, underwent instantaneous hydrogen isotope exchange reactions between H2O and D2O or between D2O and H2 gas molecules. The efficiency of the atmospheric pressure discharge was assessed by measuring the extent of the exchange reactions at a given flow rate of the gas mixture.

Reactivity of Normal Chain Diols in T-for-H Exchange Reaction

In order to clarify the reactivity of normal chain diols, the hydrogen-isotope exchange reaction (T-for-H exchange reaction) between solid poly (vinyl alcohol) labeled with tritium and each normal chain diol dissolved in 1, 4-dioxane has been observed in the range of 30 to 70 °C (or 90 °C) . The observed data was analyzed with the A″-McKay plot method, and the following three matters are consequently found. (1) The greater the number of methylene groups in a diol is, the smaller is the reactivity of the diol. (2) A significant difference in the reactivity is found between diols having even number of methylene groups and those having odd number of ones, and the reactivity of the former is larger than that of the latter. (3) As to the ratio of the decrease of the reactivity of the diols having increasing number of methylene groups, the ratio of diols having even number of methylene groups is greater than the ratio of diols having odd number of ones.

Combining microwave‐enhanced deuteriation reactions with parallel synthesis procedures

AbstractThe development of combined microwave‐enhanced/parallel synthesis procedures and their application to the deuteriation of organic compounds via examples of solid‐state hydrogenation is reported. Other labelling procedures, such as solution state catalytic dehalogenations, hydrogenations as well as hydrogen isotope exchange reactions also benefit from the combined technology. Copyright © 2003 John Wiley & Sons, Ltd.

Reactivity of Aliphatic Dicarboxylic Acids in Hydrogen-Isotope Exchange Reaction

In order to reveal the reactivity of aliphatic dicarboxylic acids, the hydrogen-isotope exchange reaction (T-for-H exchange reaction) between poly (vinyl alcohol) labeled with tritium at hydroxy group and one of aliphatic dicarboxylic acids in 1, 4-dioxane has been observed in a liquid-solid system in the range from 30 to 90°C. It was consequently found that (1) the greater the number of methylene groups in a aliphatic dicarboxylic acid is, the smaller is the reactivity of the acid; (2) a large difference is found between the reactivity of acids having even numbers of methylene groups and those having odd numbers, and the reactivity of the former is generally larger than that of the latter; (3) relating to the decrease of the reactivity of the acids with increasing number of methylene groups, the rate of the decrease in the case of even numbers is smaller than in the case of odd ones; (4) the reactivity of aliphatic dicarboxylic acids in T-for-H exchange reaction is largely dependent on the configuration (e.g., cisoid or transoid) of the two COOH groups.

Reactivity of Benzenesulfonic Acids in the Hydrogen-Isotope Exchange Reaction.

In order to reveal the reactivity of a functional group in an aromatic compound having two substituents in the aromatic ring, the hydrogen-isotope exchange reaction (T-for-H exchange reaction) between tritiated water vapor (HTO vapor) and 3-amino-4-methoxybenzenesulfonic acid (and 2-aminotoluene-5-sulfonic acid) was dynamically observed at 50°C (and 70°C) in a gas-solid system. Consequently, the specific activity of the acid increased with time, and it showed that the T-for-H exchange reaction occurred. Applying the A″-McKay plot method to the data observed, the rate constant of each functional group for the reaction was obtained. After the additive property of the Hammett's rule was applied to this work; the new substituent constants were obtained. From the above-mentioned, the following four items have been confirmed. (1) The reactivity of the functional groups can be dynamically analyzed, and the A″-McKay plot method is useful to analyze the reactivity. (2) The additive property of the Hammett's rule is applicable to quantitative comparison of the reactivity of the functional groups. (3) The reactivity of the functional groups can be simultaneously analyzed by using the A″-McKay plot method in the T-for-H exchange reaction. (4) The method used in this work is also useful for analyzing the reactivity of a certain material having some kinds of functional groups.

Isotope Effect in Hydrogen Isotope Exchange Reaction on First Wall Materials

Hydrogen isotope exchange reaction is an essential reaction to understand tritium behavior in a fusion reactor because non-negligible amount of tritium is considered to be trapped to the surface of various materials through the isotope exchange reaction. However, a quantitative consideration of the isotope exchange reaction on candidates for the first wall material has not been done yet. In this study we experimentally quantify the hydrogen isotope exchange reaction rates between hydrogen isotope in a gas phase and hydrogen isotope on the surface of isotropic graphite, C/C composite and SiC. The isotope effect is observed in every material used in this work. The reaction rate between H2-gas and D- surface is faster than that between D2-gas and H-surface in every material, though no isotope effect has been observed on the surface of solid breeder materials or metals as stainless steel, aluminum and copper in previous studies. It is also certified that the isotope effect on SiC surface is the largest among three materials studied in this work. The isotope effect in the isotope exchange reaction for various combination of hydrogen isotopes are estimated using Bigeleisen)s equation.

Isotope Effect in Hydrogen Isotope Exchange Reaction on First Wall Materials.

Isotope Effect in Hydrogen Isotope Exchange Reaction on First Wall Materials.

Reactivity of sulfonic acid group and estimation of its substituent-effect in T-for-H exchange reaction

The hydrogen-isotope exchange reaction (T-for-H exchange reaction) between each solid material having two different kinds of functional groups and HTO vapor has been observed at several temperatures. Solid materials used were monosubstituted aminobenzenes. The rate constant (k) for each functional group was obtained by applying both the A"-McKay plot and the date obtained. Comparing these k values quantitatively leads to the followings: (1) the A"-McKay plot is useful in obtaining the reactivity of the compounds having two different kinds of functional groups; (2) as to m-aminobenzenesulfonic acid, the reactivity of the SO3H group is about 6.6-8 times larger than that of the NH2 group, and the temperature dependence of the reactivity of the SO3H group is also larger than the dependence of that of the NH2 one; (3) the reactivity of the NH2 group of some kinds of monosubstituted aminobenzenes may follow the Hammett rule; (4) the substituent constant (s) of SO3H group is estimated as follows: sm is 0.38, and sp is 0.64; (5) the substituent-effect of SO3H group is generally larger than that of other substituents; and (6) the subsutituent-effect unknown can be estimated by applying both the Hammett rule and A"-McKay plot.

脂肪族ジカルボン酸中のメチレン数がその反応性に及ぼす影響 Ｔ‐ｆｏｒ‐Ｈ交換反応の利用

Hydrogen-isotope exchange reaction (T-for-H exchange reaction) between HTO vapor and aliphatic dicarboxylic acid having different number of methylene groups with each other has been observed at 50°C. Consequently, the quantitative relation was obtained between the reaction time and the increase of the activity of aliphatic dicarboxylic acid. The reaction was dynamically analyzed with both the A″-McKay plot method and data obtained.As to aliphatic dicarboxylic acids, the following two matters have been consequently found : (1) as the reactivity of each material decreases with increasing the number of methylene groups in the material, the effect of the number of methylene groups per molecule on the reactivity of the material can be quantitatively evaluated, (2) using the A″-McKay plot method, the reactivity of solid organic compounds can be evaluated, nondestructively.

Isotope Effects of Water Molecules on the Hydration of Alkali Metal and Halide Ions

Abstract Based on the results of hydrogen isotope fractionation in aqueous alkali halide solutions at 25 °C, reported in previous papers, the hydrogen isotope effect between water molecules hydrated to a cation or an anion and bulk water molecules is estimated with the assumption that the equilibrium constant of the hydrogen isotope exchange reaction between the hydration water of sodium ion and bulk water is unity. The orders of the hydrogen isotope effects of alkali metal cations and halide anions are found to be Cs+ > K+ > Na+ > Li+, and I− > Br− > Cl− for a constant hydration number, respectively, and the hydrogen isotope effect is mainly influenced in anions rather than in cations. The oxygen isotope effect for alkali and halide ions is evaluated from the literature. The hydrogen and oxygen isotopic effects for the cations and anions show the same trend, but the magnitude of the hydrogen isotope effect for anions is significantly larger than that of the oxygen isotope effect. The free energy of transfer of alkali metal and halide ions from H2O to HDO is calculated from the hydrogen isotope effect for the individual ions. The calculated values are compared with the free energy of transfer from H2O to D2O obtained by electromotive force measurements, and are compared with the free energy of transfer from H216O to H218O calculated from the oxygen isotope effect.

Hydrogen Isotope Exchange Reactions in an Electrical Discharge

Hydrogen isotope exchange reactions occurring in (H2O, D2)or (D2O, H2) reacting system under a DC electricaldischarge were investigated using spectroscopic methods such asFourier-transform infrared (FTIR) and plasma emission spectroscopy(PES). The progress of the reactions was determined by real-time measurementof the IR absorbance of HDO molecule, a major product of the reaction. Theprogress of the reaction was studied as a function of the temperature, thecurrent density, and the composition of the reactants, while the pressure ofthe system was maintained at approximately 67 mbar. The results revealedthat the discharge method was far more effective in facilating the exchangereaction than was the conventional catalytic method. The (H2O, D2)system also generated a significant amount of D2O besides HDO andHD as the ratio of D2 to H2O was increased. Thetransient species of the system, such as H or D atoms, were monitored duringthe discharge using emission spectroscopy. The analysis of the final products by mass spectroscopy confirmed that neither H2 nor O2was among the major products of the system in the discharge.

T-for-H exchange reaction between HTO vapor and two functional groups in an aromatic compound in a gas-solid system

The hydrogen-isotope exchange reaction (T-for-H exchange reaction) between HTO vapor and an aromatic compound having two different kinds of functional groups has been observed at several temperatures. The rate constant (k) for each functional group in the T-for-H exchange reaction was obtained by using both theA″-McKay plot method and the data observed. Comparing thesek with each other has led to the following four conclusions in the T-for-H exchange reaction. (1) The reactivity of both the COOH and OH groups increases with a rise in temperature. (2) As to the degree of the effect of the COOH group on the reactivity of monosubstituted phenols, the degree inp-hydroxybenzoic acid is greater than that inm-hydroxybenzoic acid. (3) The HAMMETT rule is useful for estimating the reactivity of a certain aromatic compound. (4) TheA″-McKay plot method is also useful not only investigating the reactivity of the compounds having one kind of functional group, but also doing the reactivity of the compounds having two different kinds of functional groups.

Experimental determination of the reaction time for hydrogen isotope exchange H2+D2→2HD on Ni(110)

The mean reaction time of the hydrogen isotope exchange reaction H2+D2→2HD on the Ni(110) surface has been measured in a high-resolution time-of-flight (TOF) scattering experiment. The reactants were supplied by a pulsed supersonic D2 nozzle beam with incident energy Ei⩽120 meV and by a room temperature effusive H2 source. The TOF spectra of the product HD molecules measured with a chopper located between the incident D2 beam and the sample are a convolution of the reaction time τ on the surface and the velocity distribution of the desorbing HD products. The latter distribution is then measured with a chopper placed between the sample and the detector. The reaction time τ as determined from a deconvolution of the two spectra decreases with increasing surface temperature Ts from τ∼3000 μs at Ts=450 K to τ∼10 μs at Ts=700 K. An Arrhenius plot of the reaction time reveals that the reaction energy is Er=440 meV at surface temperatures below about Ts=600 K and Er=790 meV for temperatures Ts>700 K. Possible interpretations for the two reaction channels are proposed.

Microwave-enhanced metal- and acid-catalysed hydrogen isotope exchange reactions

The benefits of using microwaves to accelerate the rates of hydrogen isotope exchange reactions are illustrated by reference to heterogeneous and homogeneous metal-catalysed reactions as well as to homogeneous acid-catalysed reactions. The results show that good incorporation of deuterium is obtained in very short time intervals, typically <20 min, and that the approach has considerable potential for the labeling of a wide range of compounds with both deuterium and, by implication, tritium.Key words: microwave enhanced deuteriations, hydrogen isotope exchange.

水素同位体交換反応における位置選択性

水素同位体交換反応における位置選択性

Microwave-enhanced metal- and acid-catalysed hydrogen isotope exchange reactions

Microwave-enhanced metal- and acid-catalysed hydrogen isotope exchange reactions

Effect of Substituents on the Reactivity of Monosubstituted Benzyl Mercaptans in Hydrogen-Isotope Exchange Reaction

Article Effect of Substituents on the Reactivity of Monosubstituted Benzyl Mercaptans in Hydrogen-Isotope Exchange Reaction was published on August 1, 1997 in the journal Radiochimica Acta (volume 79, issue 1).

Kinetics of iodine poisoning of hydrophobic Pt/SDBC catalyst for hydrogen isotopic exchange reaction

AbstractChanges with time in the isotopic exchange reaction rate between H2 and HDO(v) over a hydrophobic Pt/SDBC (styrene‐divinylbenzene copolymer) catalyst induced by iodine have been studied experimentally. The addition of a trace amount of I2 to the reactor caused a remarkable decrease in the activity of the catalyst. The measurement results by means of the gas chromatographic pulse technique show that the H2 adsorption onto the catalyst surface was strongly inhibited by iodine. A kinetic model for the poisoning was developed in terms of the competitive adsorption of I2 with H2 onto the catalytic active site. The experimental results were explained reasonably by the proposed kinetic model based on the site balance by assuming that I2 adsorbs non‐dissociatively on the active site. The poisoning could be prevented by the conversion of I2 to I− or IO3−through redox reactions.

Effect of the Number of Methylene Groups per Molecule on the Reactivity of Both Amino and Carboxyl Groups in Hydrogen-Isotope Exchange Reaction

Article Effect of the Number of Methylene Groups per Molecule on the Reactivity of Both Amino and Carboxyl Groups in Hydrogen-Isotope Exchange Reaction was published on March 1, 1997 in the journal Radiochimica Acta (volume 76, issue 4).

Regioselective Hydrogen Isotope Exchange Reaction in Benzoic Acid and Its Alkali Metal Salts.

The hydrogen isotope exchange reaction of benzoic acid and its alkali metal salts with deuterium oxide was studied in the presence of RhCl3⋅3H2O. The products were analyzed by 1H-and 13C-NMR spectroscopies. High regioselectivity of the exchange at the ortho positions was established, and the extent of deuterium labeling and the distribution of d0, d1, and d2 were determined. The reaction mechanism was briefly discussed.