Models, for hydrogen-bonded

Abstract—A one-dimensional model for hydrogen bonding based on a potential function and previously applied to O—H——O systems has been extended and applied tc... 

VT John W. Hill, "A People-and Velcro Model for Hydrogen Bonding," /. Chem. Educ., Vol. 67, 1990, 223. 

Domain model for hydrogen bonding involving metal complexes. Here D and A represent donor and acceptor atom, respectively. Note that both M-H and D-H units remain intact. 

Figure 3 Domain model for hydrogen bonding involving metal complexes. Metal Domain (blue) Ligand Domain (green) Periphery Domain (red) Environment (cyan) (see also Plate 1).

From = iv/(l - 8aecos0/a3) with pv = 1.86 D, we obtain tv = 2.138 D for the effective dipole moment in liquid water from the 298 K bulk dielectric constant. When this is used to estimate the cohesive energy between water molecules in approximately tetrahedral superdipoles at dipole-dipole or O O distances of 2.9 A, the results are about a factor of three too small. The simple dipole-dipole model for water was therefore replaced by a DP multipole-multipole point charge model for hydrogen bonding (c.f., Lih173), and the interactions... 

Z. Zhang, J. Toboehnik, M. J. Zuckermann, and J. Silvins, Lattice model for hydrogen bonding and hydration in pure lipid bilayers. Phys. Rev. E, 47 (1993), 3721-3729. 

Giese, T. J., Sherer, E. C., Cramer, C. J., and York, D. M. (2005]. A semiempirical quantum model for hydrogen-bonded nucleic acid base pairs,/. Chem. Theory Comput 1(6], 1275-1285. 

Structure 2. Classic electrostatic model for hydrogen bond. 

J. Parra-Mouchet, R.R. Contreras and A. Aizman, Self-consistent reaction field calculations on the proton transfer in ammonia-formic acid systems as a model for hydrogen bonding in amino acids in solution, Int. J. Quantum Chem., 33 (1988) 41. 

The pathway model makes a number of key predictions, including (a) a substantial role for hydrogen bond mediation of tunnelling, (b) a difference in mediation characteristics as a function of secondary and tertiary stmcture, (c) an intrinsically nonexponential decay of rate witlr distance, and (d) patlrway specific Trot and cold spots for electron transfer. These predictions have been tested extensively. The most systematic and critical tests are provided witlr mtlrenium-modified proteins, where a syntlretic ET active group cair be attached to the protein aird tire rate of ET via a specific medium stmcture cair be probed (figure C3.2.5). 

One proposed approach (75) to modeling the phase behavior for hydrogen bonding pairs uses the following expression for the free energy of mixing (eq. 7). 

Some force fields make special provision for hydrogen-bonded atoms A-H B, and modify the Lennard-Jones 12-6 potential to a 12-10 model ... 

Recently, Vayner and coworkers [239] have revisited the model proposed by Augustine et al. [34] which is based on the assumption that the QN can make a nucleophilic attack to an activated carbonyl. According to this model the two possible zwitterionic intermediates that can thus be formed have different energies, which leads to the selective formation of one of the two intermediates, and, therefore, to e.s. after hydrogenolysis by surface hydrogen. This model nevertheless does not explain the e.d. of nonbasic modifiers, such as the one reported by Marinas and coworkers [240], which have no quinuclidine moiety and no nitrogen atom, and thus no possibility to form zwitterionic intermediates. Furthermore, in situ spectroscopic evidence for hydrogen bond formation between the quinuclidine moiety of cinchonidine and the ketopantolactone has been provided recently [241], which supports the hypothesis of the role of weak bond formation rather than the formation of intermediates such as those proposed by Vayner and coworkers. 

The object of this work was to extend the field of application of the equation-of-state method. The method was applied to aqueous systems in conjunction with a model that treats water as a mixture of a limited number of polymers, an approach similar to that previously adopted for the carboxylic acids (2). Association is calculated by the law of mass action corrections for non-ideal behaviour are made by means the equation of state. A major problem of the method is the large number of parameters needed to describe the properties and concentrations of the polymers together with their interaction with molecules of other substances. The Mecke-Kemptner model (15) (also known as the Kretschmer-Wiebe model (16) and experimental values for hydrogen-bond energies were usecT for guidance in fixing these parameters. 

---