Nitrogen atoms, calorimetric determination

Pressure and temperature effects on the reaction rate of dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate with 1-hexene have been investigated. The activation volume (—26.7cm moP, 298.1 K) is in agreement with the conservation of all four nitrogen atoms in the transition state. Densitometry, H NMR, and calorimetric studies of the reaction indicate nitrogen molecule loss by the intermediate just after its formation. Partial molar volumes in acetone of diene (127.2), 1-hexene (127.6), and the resulting adduct (206.9cm moP ) have been determined <1999T12201, 1999DOK498>. 

A range of cations, notably Fe catalyse the reaction and also reduce the ratio N2/N2O in the product. It is claimed that when such cations are completely com-plexed, decomposition does not occur. A mechanism involving decomposition of hydroxylamine complexes of Fe Cu, or Co is preferred. Calorimetric determinations of the heat of solution of a range of alkylhydrazines in water, and in 0.1 mol dm hydrochloric acid, have been correlated in terms of a constants and hydration parameters. This enables calculations of the relative basicities of the two nitrogen atoms in an unsymmetrical alkylhydrazine to be made. This may be of value in interpreting the mechanism of oxidation of the alkylhydrazines. The mechanisms involved in the synthesis of NF4+[AsFj] from NFj, AsFg, and Fg have been discussed, and an alternative mechanism to that suggested earlier has been proposed for the thermal decomposition of NF4+[AsFe]. ... 

The kinetics of reaction (29) have been investigated by rapid-scan i.r. spectroscopy. The experimental rate constant is in reasonable agreement with an earlier calorimetric value, but the use of isotopic NO has now established the reaction mechanism to be a Cl atom transfer. Rate constants for the nitrogen isotope exchange reactions (30) and (31) have also been determined. ... 

The study of the complexes of the rare earth elements has been marked by several periods of renewed interest. As already mentioned, the first intensive work was carried out to find those ligands which would be effective in conjunction with ion exchange or in solvent extraction procedures for the separation of the elements one from another. In the initial phase these studies focused primarily on the determination of equilibrium constants and distribution coefficients (Moeller et al., 1965). The compounds that were studied as ligands in both cases were almost exclusively limited to molecules that used oxygen as the donor atom, either alone, or as in the case of the aminopolycarboxylic acids, in combination with nitrogen donors within the same molecule. This phase started in the early 1940 s and lasted into the I960 s. Toward the end of this period the equilibrium measurements were supplemented with calorimetric studies of the enthalpy of formation of the complexes in solution in order to define more clearly the nature of the complexation process (Moeller, 1973). However, during much of this time there was very little effort devoted to the study of the solid complexes which could be isolated from solutions. 

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