Polarity proton transfer reactions

Lobaugh J and Voth G A 1994 A path integral study of electronic polarization and nonlinear coupling effects in condensed phase proton transfer reactions J. Chem. Phys. 100 3039... 

A Warshel. Dynamics of reactions m polar solvents. Semiclassical trajectory studies of electron-transfer and proton-transfer reactions. J Phys Chem 86 2218-2224, 1982. 

A large red shift observed in polar solvents was indicative of the intramolecular charge transfer character of the triplet state. The change of dipole moment accompanying the transition Tj - Tn, as well as rate constants for electron and proton transfer reactions involving the T state of a-nitronaphthalene, were determined. The lower reactivity in polar solvents was attributed to a reduced n-n and increased charge transfer character of the triplet state... 

A proton transfer reaction involves breaking a covalent bond. For an acid, an H — X bond breaks as the acid transfers a proton to the base, and the bonding electrons are converted to a lone pair on X. Breaking the H — X bond becomes easier to accomplish as the bond energy becomes weaker and as the bonding electrons become more polarized toward X. Bond strengths and bond polarities help explain trends in acidity among neutral molecules. 

At least three components of the system change their state in the case of proton transfer reaction (1) electrons of the water molecule and the electrode providing the chemical bonding of the proton with a water molecule and the metal surface, (2) the proton itself, and (3) medium polarization. The characteristic times x, Xp, and x for... 

This type of charge reduction by charge transfer to the solvent molecule occurs in general when SI are polar solvent molecules of aprotic character such as dimethyl-sulfoxide, dimethyl formamide, and acetonitrile. Protic solvents such as water lead to charge reduction which involves an intracluster proton transfer reaction ... 

Kiefer PM, Hynes JT (2002) Nonlinear free energy relations for adiabatic proton transfer reactions in a polar environment. I. Fixed proton donor—acceptor separation. J Phys Chem A... 

German ED, Kuznetsov AM, Dogonadze RR (1980) Theory of the kinetic isotope effect in proton transfer reactions in a polar medium. J Chem Soc, Faraday Trans 2 76 1128-1146... 

Chou PT, Yu WS, Cheng YM et al (2004) Solvent-polarity tuning excited-state charge coupled proton-transfer reaction in p-N, N-ditolylaminosalicylaldehydes. J Phys Chem A 108 6487-6498... 

The new treatment had its origins partly in ab initio molecular orbital calculations of substituent effects and partly in extensive studies of gas-phase proton transfer reactions from about 1980 (Section V.A). Various aspects of this work essentially drew attention to the importance of substituent polarizability. In 1986 Taft, Topsom and their colleagues252 developed a scale of directional substituent polarizability parameters , oa, by ab initio calculations of directional electrostatic polarization potentials at the 3-21G//3-31G level for a large set of CH3X molecules. The oa values were shown to be useful in the correlation analysis of gas-phase acidities of several series of substrates252, and such work has subsequently been extended by Taft and Topsom151. 

Atmospheric pressure chemical ionization APCI is a method closely related to electrospray ionization. It uses ion-molecule reactions to produce ions from analyte molecules. The sample is electrohydrodynamically sprayed into the source (Figure 14.3). The evaporation of the solvent is often supported by a heated gas at temperatures between 80 and 400°C. Within the source, a plasma is created using a corona discharge needle that is placed close to the end of the metal capillary. In this plasma, proton transfer reactions occur, leading to the ionization of the analyte, mainly by the formation of [M+H]+ ions. Compared to ESI MS, APCI MS is very well suited for the analysis of less-polar components and can therefore... 

It had been anticipated that the reaction pathway for a proton transfer reaction should be characterized by a double minima in the potential surface.100 The failure of Qementi s calculation to predict a barrier along the reaction pathway for the transfer of H + from HQ to NH3 to form NHJC1-, must be accepted with some caution in view of the lack of polarizing functions on N and Cl in the basis set. This work, however, broke new ground and dementi99 includes in his paper a detailed discussion of the merits and faults to be expected for the Hartree-Fock method in the different regions of the potential surface. 

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