Hydrogen-transfer interactions

Wolin MJ (1982) Hydrogen transfer in microbial communities. In Microbial interactions and communities (Eds AT Bull, JH Slater), Vol. 1, pp. 323-356. Academic Press, New York. 

In the Born equation, the ion solvent interaction energy is determined only by one physical parameter of the solvent, i.e., the dielectric constant. However, since actual ion-solvent interactions include specific interactions such as the charge-transfer interaction or hydrogen bonds, it is natural to think that the Born equation should be insufficient. It is well known that the difference in the behavior of an ion in different solvents is not often elucidated in terms of the dielectric constant. 

Tram-anular interactions, which would create an active radical site via hydrogen transfer through 98, cannot be invoked to explain the specific loss of a CH3 radical from the ether side chain. This conclusions is based upon the following experimental observations. The radical cation of the tetrafluoro substituted compound 101 eliminates CH3, but loss of CH3 from the para-isomer 102 is not observed. If a transanuiar process according to 97- 98 were operative, then such a reaction is not expected to be suppressed upon substitution of H by F as is known for many examples from the field of photochemistry of fluoro substituted compounds41 (23). 

Interestingly, the nature of allowed donor-acceptor interactions suggests that donor class will be conserved in any hydrogen transfer sequence. Thus a (4n+2)e donor, say, will transfer hydrogen to a (4m)e acceptor, and the latter, upon accepting the hydrogen, will evidently become a (4m+2)e donor, of the same class... 

The general or universal effects in intermolecular interactions are determined by the electronic polarizability of solvent (refraction index n0) and the molecular polarity (which results from the reorientation of solvent dipoles in solution) described by dielectric constant z. These parameters describe collective effects in solvate s shell. In contrast, specific interactions are produced by one or few neighboring molecules, and are determined by the specific chemical properties of both the solute and the solvent. Specific effects can be due to hydrogen bonding, preferential solvation, acid-base chemistry, or charge transfer interactions. 

Dumas, J.-M., H. Peurichard, and M. Gomel. 1978. Base Interactions as Models of Weak Charge Transfer Interactions Comparison with Strong Charge-Transfer and Hydrogen-bond Interactions. J. Chem. Res. (S), 54. 

Neither tritium or deuterium gas, with zero dipole moments, can be expected to interact positively with microwave radiation. Their low solubilities are seen as a further disadvantage. Our thoughts therefore turned towards an alternative procedure, of using solid tritium donors and the one that has found most favor with us is formate, usually as the potassium, sodium or ammonium salt. Catalytic hydrogen transfer of this kind is remarkably efficient as the results for a-methylcinnamic acid show [50]. The thermal reaction, when performed at a temperature of 50 °C, takes over 2 h to come to equilibrium whereas the microwave-enhanced reaction is complete within 5 min. A further advantage is that more sterically hindered al-kenes such as a-phenylcinnamic acid which are reduced with extreme difficulty when using H2 gas and Wilkinson s catalyst are easily reduced under microwave-enhanced conditions. 

MPA-bridged SOD-electrode complex could be formed via a variety of interactions between MPA and the SODs, such as electrostatic, hydrophobic, and/or hydrogen bonding interactions, which is believed to be responsible for the observed direct electron transfer properties of the SODs. Besides, such interactions substantially enable the SODs to be stably confined at the MPA-modilied Au electrode, which can be further evident from the re-observation of the redox responses of SODs in a pure electrolyte solution containing no SOD with the MPA-modified electrode previously used in SOD solutions. 

The metabolism studies with cyanide present showed no dehydrogenation whatsoever of the substrate. It is thus considered likely that the resazurin and the resorufin interact with some metal bearing system, possibly the cytochromes participating in the hydrogen transfer. Although the resazurin (or resorufin) may interact in a system several steps removed from the dehydrogenation of the particular substrates, the relative rates of reduction of the indicator are still comparable with the relative oxidation rates of the substrates. 

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