Water H-bonding

Basch, H., and W. J. Stevens. 1990. The Structure of Glycine-Water H-Bonded Complexes. Chem. Phys. Letters 169, 275-280. 

Soluble in water H-bonding, acid strength given by pKa... 

The overall structure of the supercluster has the following topology (Figure 6) where each vertex represents one of the two central Mo atoms (one inside the other relative to the sphere) in the linking (Mo)Mo5 groups holding the water H-bonded connecting clusters. 

Figure 44. A schematic model of glycerol-water H-bonding liquids in different concentration of components.

Modeling Chiral Solute-Water H-Bonding Networks by Induced Solvent Chirality... 

High-quality ab initio calculations of various cluster models, were in favor of the view that water is only physisorbed on the zeolite and found that the proton-transferred hydronium ion structure is a transition state between two minima corresponding to the water H-bonded to the acid site (cf. Fig. 5). 

This behavior reflects a competition between the energy needed to break the bulk hydrogen-bonded structure and the strength of the ion-water interaction. From 298 to 373 K, it is increasingly easier for water molecules to leave the ionic first shell (Cl, K+ and Rb+) than to break the tight H-bond water network. At T > 373 K, the behavior reverses. The water H-bond network is disrupted and the water-ion attraction becomes again predominant over the water-water interactions. For Na", on the other hand, the ratio of residence times remains approximately constant in spite of the increase in temperature due to the strong ion-water interaction. Dynamic hydration numbers reflect these trends, as seen in Table 11. 

Note that the partial covalent character means that they are directional Compare the bond length of water H bonds (0.18 nm) to the covalent bond-length between O and H of 0.096 nm - notice that the bond distance is nearly twice the true covalent bond distance, but significantly less than the van der Waals radius of 0.26 nm. 

Novel H-bond involving aromatic rings have been an important subject in the last decade [4]. The comparison of rr-type H-bond interaction with the traditional water-water o-type H-bond interaction should be very interesting. The interaction energies of ethylene-water tt-H bond and water-water H-bond interactions were calculated to be 2.84 + 0.59 and 4.89 + 0.41 kcal/mol at the MP2/aVDZ level, where the lower and upper limits are the BSSE-corrected and -uncorrected values, respectively. 

Several other molecules can make H bonds with one another, but if they are dissolved in water, H bonds between solute and water are preferentially formed in most cases the various H bonds are of about the same strength, and association of solute molecules would lead to loss of entropy. This implies that strong hydrogen bonding especially occurs in an apolar solvent, for instance between the carboxyl groups of fatty acids in oil, as discussed in Section 2.2.5, point 4. 

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