Hydrogenation theoretical investigations

Most studies concerning pyrimidines originate from biochemical questions. Since these systems are dominated by hydrogen-bonding and/or dispersion contributions, methods beyond the Hartree-Fock level are mandatory. The success of quantum chemical studies in this field is impressive and many effects could be explained on the basis of these theoretical investigations. 

The properties of the hydrogen molecule and molecule-ion which are the most accurately determined and which have also been the subject of theoretical investigation are ionization potentials, heats of dissociation, frequencies of nuclear oscillation, and moments of inertia. The experimental values of all of these quantities are usually obtained from spectroscopic data substantiation is in some cases provided by other experiments, such as thermochemical measurements, specific heats, etc. A review of the experimental values and comparison with some theoretical... 

Kumar, G. A., McAllister, M. A., 1998, Theoretical Investigation of the Relationship Between Proton NMR Chemical Shift and Hydrogen Bond Strength , J. Org. Chem., 63, 6968. 

A damantane-type cage hydrocarbons have become a new target of theoretical investigation. The tertiary hydrogens which are known to be... 

A number of theoretical works have been devoted to the study of the hydrogen-deuterium exchange reaction. Hauffe (25) examined this reaction from the standpoint of the boundary layer theory of chemisorption. Dowden and co-workers (26) undertook a theoretical investigation of the hydrogen-deuterium exchange reaction from the viewpoint of the theory of crystalline fields. 

Although several hydrogen double-acceptor pairs have been identified in semiconductors, few theoretical investigations have been reported. Much... 

As briefly discussed in section 1.1, and shown in Figure 1, the accepted mechanism for the catalytic cycle of hydrogenation of C02 to formic add starts with the insertion of C02 into a metal-hydride bond. Then, there are two possible continuations. The first possibility is the reductive elimination of formic acid followed by the oxidative addition of dihydrogen molecule to the metal center. The second possible path goes through the a-bond metathesis of a metal formate complex with a dihydrogen molecule. In this section, we will review theoretical investigations on each of these elementary processes, with the exception of oxidative addition of H2 to the metal center, which has already been discussed in many reviews. 

Theoretical investigations of AEV and AEC have indicated that the ratio AEV/AEC is greater than 1 [Zh2, Vo2, Ne2] and may be as high as 3 for the case of hydrogenated silicon clusters [Re3], In a similar calculation for thin silicon films, even-odd oscillations of A v according to the number of Si monolayers have been found [Zh2], For the latter case the ratio AEy/AEc showed values between 1 and 2. The results of a study [Wa5] including the decrease in the static dielectric constant with size are close to the experimentally [Bu2] observed values of about 2 for the ratio AEy/AEc, as shown in Fig. 7.16. In this work [Wa5], it is concluded that the electron-hole pair is confined by the physical dimension of the quantum dot, not by Coulomb attraction. 

Scott, A. P. Golding, B. T., Random, T. (1998) Remarkable cleavage of molecular hydrogen without the use of metallic catalysts a theoretical investigation. New J. Chem., 22, 1171-3. 

In contrast to those noted above, theoretical investigations of branched complexes in which two or more hydrogen bonds are formed by one proton-acceptor group, as in Structure 2.4, predict an inverse effect. In this case, mutual polarization weakens the hydrogen bonds, leading to anticooperative effects. The various factors governing the influence of the first hydrogen bond on the formation of... 

This paper reports some results of our theoretical investigations on the hydrogen bond. The original papers have been published in Russian and they are therefore little known in other countries. 

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