Multiple proton transfers

Drukker, K., Hammes-Schiffer, S. An analytical derivation of MC-SCF vibrational wave functions for the quantum dynamical simulation of multiple proton transfer reactions Initial application to protonated water chains. J. Chem. Phys. 107 (1997) 363-374. 

Hammes-Schiffer Multiconflgurational molecular dynamics with quantum transitions Multiple proton transfer reactions. J. Chem. Phys. 105 (1996) 2236-2246. 

Since the actual number of protons transferred between the analyte and titrant is uncertain, we define the analyte s equivalent weight (EW) as the apparent formula weight when = 1. The true formula weight, therefore, is an integer multiple of the calculated equivalent weight. 

Kinetics of the Multiple-Proton Transfer in Cyclic Associates of Pyrazoles [89JA7304, 97JCS(P2)101]... 

Zhang, Q., Bell, R., Truong, T. N., 1994, Ab Initio and Density Funcional Theory Studies of Proton Transfer Reactions in Multiple Hydrogen Bond Systems , J. Phys. Chem., 99, 592. 

In most (but certainly not all ) experiments involving ion-molecule reactions, the structure of the product ions is not determined. As the number of atoms in the product ions increases, the multiplicity of possible isomers becomes greater. Knowledge of the structure of ions is critical in determining what neutral products result from dissociative recombination. Although some classes of ion-molecule reactions, such as proton transfer reactions, lead to products with relatively well-characterized structures, the problem can be more severe with other classes of reactions. 

The most important multiply charged polyatomic positive ions are compounds with two or more basic groups which when protonated lead to doubly or poly-charged ions. Typical examples are diamines such as the double protonated a, to alkyldiamines, H3N(CH2)pNH2+, and the most important class, the polyprotonated peptides and proteins, which have multiple basic residues. Charge reduction for these systems occurs through proton transfer from one of the protonated basic sites to a solvent molecule. Such a reaction is shown below for the monohydrate of a doubly protonated diamine ... 

Chattoraj M, King BA, Bublitz GU, Boxer SG (1996) Ultra-fast excited state dynamics in green fluorescent protein multiple states and proton transfer. Proc Natl Acad Sci USA 93 8362-8367... 

Chattoraj, M., King, B. A., Bublitz, G. U. and Boxer, S. G. (1996). Ultrafast excited state dynamics in green fluorescent protein Multiple states and proton transfer. Proc. Natl. Acad. Sci. USA 93, 8362-7. 

Most of the AIMD simulations described in the literature have assumed that Newtonian dynamics was sufficient for the nuclei. While this is often justified, there are important cases where the quantum mechanical nature of the nuclei is crucial for even a qualitative understanding. For example, tunneling is intrinsically quantum mechanical and can be important in chemistry involving proton transfer. A second area where nuclei must be described quantum mechanically is when the BOA breaks down, as is always the case when multiple coupled electronic states participate in chemistry. In particular, photochemical processes are often dominated by conical intersections [14,15], where two electronic states are exactly degenerate and the BOA fails. In this chapter, we discuss our recent development of the ab initio multiple spawning (AIMS) method which solves the elecronic and nuclear Schrodinger equations simultaneously this makes AIMD approaches applicable for problems where quantum mechanical effects of both electrons and nuclei are important. We present an overview of what has been achieved, and make a special effort to point out areas where further improvements can be made. Theoretical aspects of the AIMS method are... 

Such variation in the lifetimes of the ion pairs, which depends on the mode of activation, primarily arises from the difference in the spin multiplicities (see above). None the less, the long-lived ion-radical pair allows the in-cage proton transfer from the cation radical ArMe+ to the CA- anion radical to effectively compete with the back electron transfer,205 i.e.,... 

The basic catalyst in the isomerization of 1,2-butadienes to butynes acts by removing an alkenic proton from the hydrocarbon. Two different anions can be formed, each of which is stabilized by electron delocalization involving the adjacent multiple bond. Either anion can react with the solvent by proton transfer to form the starting material or an alkyne. At equilibrium the most... 

Multiple cyclic proton transfers occur in hydrogen bonded arrays of heterocyclic units [8.220, 8.221] or inside rings such as porphyrins [8.222]. Macrocyclic polyamines present various protonation patterns [3.13a] that could be of interest as information units. Data storage in a molecular memory by hole burning makes... 

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