Isotopic hydrogen exchange, liquid

Originally Horiuti, Ogden and Polanyi (68) considered both the dissociative and associative mechanism as possible explanations of the isotopic hydrogen exchange between liquid benzene and heavy hydrogen in the presence of platinum black. Subsequently, Horiuti and Polanyi decided in... 

The present paper is a brief review of investigations concerned with the study of hydrogen exchange in liquid ammonia, which have been carried out by the author in collaboration with Yu. P. Vyrskii, N. M. Dykhno, E. A. Izrailevich, E. A. Yakovleva, E. N. Zvyagintseva, A. V. Vedeneev, Yu. I. Ranneva, and other workers at the Isotope Reaction Laboratory. 

Hydrogen isotope exchange reactions have long been used to prepare deuterated organic compounds (Miklukhin, 1961). The extension of the range of substances which can take part in hydrogen exchange reactions, which has been the result of the use of liquid deuterio-ammonia as the reactive medium, has opened new possibilities as far as such preparations are concerned (Shatenshtein and Izrailevich, 1957 Bardasova et al., 1960). 

Comparison of results on hydrogen exchange in liquid ammonia and in other solvents can be used to obtain information on the nature and mechanism of hydrogen isotope exchange reactions. 

Isotopic Exchange between Hydrogen and Liquid Ammonia Catalyzed by Alkali Amides... 

Many ionic liquids are based on N,N-dialkylimidazolium cations (BMI) which form salts that exist as liquids at, or below, room temperature. Their properties are also influenced by the nature of the anion e. g. BF T PFg. The C-2(H) in imidazole is fairly labile but the C-4(H) and the C-5(H) are less so. Under microwave-enhanced conditions it is therefore possible to introduce three deuterium atoms (Scheme 13.4). As hydrogen isotope exchange is a reversible reaction this means that the three deuterium atoms can be readily exchanged under microwave irradiation. For storage purpose it might be best to back-exchange the C-2(D) so that the 4,5-[2H2] isotopomer can be safely stored as the solid without any dangers of deuterium loss. The recently... 

Exchange reactions, hydrogen isotope, of organic compounds in liquid ammonia, 1, 156 Exchange reactions, oxygen isotope, of organic compounds, 2, 123 Excited complexes, chemistry of, 19,1 Excited molecules, structure of electronically, 3, 365... 

Hydrogen isotope exchange reactions of organic compounds in liquid ammonia, 1, 156... 

For geologic purposes, the dependence of the equilibrium constant K on temperature is the most important property (4). In principle, isotope fractionation factors for isotope exchange reactions are also slightly pressure-dependent because isotopic substitution makes a minute change in the molar volume of solids and liquids. Experimental studies up to 20kbar by Clayton et al. (1975) have shown that the pressure dependence for oxygen is, however, less than the limit of analytical detection. Thus, as far as it is known today, the pressure dependence seems with the exception of hydrogen to be of no importance for crustal and upper mantle environments (but see Polyakov and Kharlashina 1994). 

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