Solvation and hydrogen bonding

The conformation that a furanoid compound will adopt in the crystal is not readily predicted. A furanoid compound can adopt one of four envelope conformations in which C-2 or C-3 is endo or exo, namely, 2E, E2, 3E, and E3 less commonly, it may adopt a twist conformation. The energy difference between the four common envelope conformations may be so slight that other effects predominate in determining the conformation that the compound will adopt, both in the crystal and in solution. Such effects include those caused by hydrogen bonding, solvation, and close contacts with an aglycon. 

Molecular mechanics with special treatment of hydrogen bonding, solvation, and metal ions. Also Yak for receptor modeling based on directionality of potential binding points on a ligand. VAX, Silicon Graphics, and Evans 8c Sutherland. 

The most important noncovalent interactions in these transitions are hydrogen bonding, solvation, and hydrophobic interactions. The dynamics of these processes have been extensively studied in model systems, and the results obtained provide some insight into the corresponding processes in proteins [21]. 

One of the most valuable techniques available to any kind of spectroscopist is that of isotopic substitution. This paper will discuss a few applications of the method to problems in the optical spectroscopy of atoms, diatomic and small polyatomic molecules, the vibrations of transition metal ccmplexes, hydrogen bonding, solvation, and optical activity. We shall, not treat either magnetic resonance or microwave spectroscopy. 

Abraham, M. H., Zhao, Y. H. Determination of solvation descriptors for ionic spedes hydrogen bond addity and basicity. J. Org. Chem. 2004, 69,... 

Other studies conducted on mixed protonated clusters of ammonia bound with TMA showed that the ion intensity distributions of (NH3)n(TMA)mH+191 display local maxima at (n,m) = (1,4), (2,3), (2,6), (3,2), and (3,8). Observation that the maximum ion intensity occurs at (n,m) = (1,4), (2,3), and (3,2) indicates that a solvation shell is formed around the NHJ ion with four ligands of any combination of ammonia and TMA molecules. In the situation where the maximum of the ion intensity occurs at (n,m) = (2,6) and (3,8), the experimental results suggest that another solvation shell forms which contains the core ions [H3N-H-NH3]+ (with six available hydrogen-bonding sites) and [H3N-H(NH2)H-NH3]+ (with eight available hydrogen-bonding sites). The observed metastable unimolecular decomposition processes support the above solvation model. 

Cornell, W. D. Cieplak, P. Bayly, C. I. Kollman, P. A., Application of RESP charges to calculate conformational energies, hydrogen bond energies, and free energies of solvation, J. Am. Chem. Soc. 1993,115, 9620-9631. 

The accurate determination of gas-phase basicities and gas-phase acidities opened the way to analyses of the effect of solvation on proton acidities, and on hydrogen-bond acidities and basicities, as well as on substituents effects. 

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