Proton transfer complexes

The electron transfer involved in the formation of a charge transfer complex may in suitable systems be coupled to a proton transfer, resulting in proton transfer complexes. This holds, especially for surface reactions, e.g., at electrodes, and a fortiori in nonaqueous media, because the proton affinity of water is so very high, viz., about 8.9 

In the gas phase, where there are energy contributions from solvation or polarization, Ap may be measured by means of ion cyclotron spectroscopy.Proton affinities are often given in kJ/mole 1 kJ/mole equals 0.0104 eV 1 kcal/mole equals 0.0436 eV. Exchange repulsion energies do not enter into proton affinities.The relative protonicity of solvents, akin to the donicity concept for electrons, is discussed by Bayless et alP  

Hydroxy-dinitro pyridines, e.g., act as electron acceptors and/or as proton donors to, e.g., napthalene derivatives. 

The field of protonic CTC has been opened up by Matsunaga and his school,and has been reviewed by Morokuma. This author points to the close linkage existing in such adducts between proton and concurrent electron transfer one does not occur without the other. The proton complex is said to involve an electron transfer from, e.g., an amine to the 

Proton transfer may, sometimes, be really nothing more than a case of conventional hydrogen bonding, but in many cases the simultaneous transfer of an electron and a proton produces a new different type of adduct then the difference between mere hydrogen bonding and complex formation may indeed be dramatic, as pointed out by Arnett and Mitchell. There is no correlation between the heats of protonation and of hydrogen bonding.  

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Aminosilanes contain the catalyzing amine function in the organic chain. The reaction of aminosilanes with silica gel in dry conditions is therefore self-catalyzed. They show direct condensation, even in completely dry conditions. Upon addition of the aminosilane to the silica substrate, the amine group may form hydrogen bonds or proton transfer complexes with the surface silanols. This results in a very fast adsorption, followed by direct condensation. This reaction mechanism of APTS with silica gel in dry conditions, is displayed in figure 8.9. After liquid phase reaction, the filtered substrate is cured, in order to consolidate the modification layer. 

Charge transfer may not be confined to electron donation transfer can also involve protons in certain cases to yield proton transfer complexes... 

The transition from a hydrogen-bonding complex (O—H N) to a proton-transfer complex (O- +H—N) can be followed by IR spectroscopy. The IR spectra of SRC-II-Acid and SRC-II-Acid + Et3N mixture at 0.69 mole fraction of SRC-II-Acid are shown in Figure 5. Absorption bands at 2680 cm-1 and 2500 cm-1, ascribed to N+—H O (18, 19) and a broad absorption band at 3200-3600 cm-1 clearly indicates the presence of both OH N and O- +H—N species in the SRC-II-Acid + Et3N system. The self-association of SRC-II-Acid is obvious from the IR spectrum of neat SRC-II-Acid. 

Here, we give place to a review concerning the effect of solvation on the - in comparison to H N HCl - more covalent proton transfer complex considering the methods mentioned till now ... 

Bimolecidar reactions include ion-pairing, proton transfer, complexation, and dimerization, to cite a few. 

Proton-transfer complexes. Preferential solvation of p-nitrophenol-amine com- 280 plexes in nonaqueous solvent mixtures... 

J. J. I. Timoneda and J. T. Hynes, /. Phys. Chem., 95, 10431 (1991). Nonequilibrium Free-Energy Surfaces for Hydrogen-Bonded Proton-Transfer Complexes in Solution. 

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