Crystals hydrogen bonded

There are many instances where hydrogen bonds formed between two electronegative atoms like oxygen or fluorine determine the stability and properties of crystals. When a 

---

The various types of successful approaches can be classified into two groups empirical model calculations based on molecular force fields and quantum mechanical approximations. In the first class of methods experimental data are used to evaluate the parameters which appear in the model. The shape of the potential surfaces in turn is described by expressions which were found to be appropriate by semiclassicala> or quantum mechanical methods. Most calculations of this type are based upon the electrostatic model. Another more general approach, the "consistent force field method, was recently applied to the forces in hydrogen-bonded crystals 48> 49>. 

Nonlinear spectroscopy study of vibrational self-trapping in hydrogen bonded crystals... 

He first graduated, in 1928, at the University of Sheffield, where he became a lecturer in chemistry, with research interests chiefly in the electrochemical field. In 1946 he moved to J. M. Robertson s laboratory at Glasgow, and his interests then began to turn towards crystal-structure analysis by x-rays and neutrons. He has applied Robertson s methods mainly to the study of hydrogen-bonded crystals and his preoccupation with this topic continues. 

E. Matsushita, T. Matsubara, Note on isotope effect in hydrogen bonded crystals. Progr. Theoret. Phys. 67, 1-19 (1982)... 

Zacharias, D. E. and Desiraju, G. R. (1993). Solid-state supramolecular assembly via C—H O hydrogen bonds - crystal structures of the complexes... 

Similar shortening of the C-N bond and lengthening of the C=0 bond is found when the structures of acetamide [376, 377], fluoroacetamide [299], and thioacetamide [204] in the hydrogen-bonded crystals are compared with ab-initio molecular orbital calculations for the isolated molecule, as shown in Thble 5.4. 

The alditol crystal structures are conformationally homogeneous. The cocrystallization of different conformers of the same molecule is not common, but sufficient examples are known, especially in hydrogen-bonded crystal structures, for it to be a phenomenon with which crystallographers are familiar. It occurs when there is a population of conformers in solution, all of which have similar energies. A classical example is that of 2,3-dimethyl-2,3-butanediol (pinacol)... 

Nagle JF (1966) Lattice statistics of hydrogen bonded crystals. I. The residual entropy of ice. J Math Phys 7 1484-1491... 

Lifson S, Hagler AT, Dauben P (1979) Consistent force field studies of intermolecular forces in hydrogen bonded crystals. I. Carboxylic acids, amides and the C-O—H hydrogen bonds. J Am Chem Soc 101 5111-5121... 

Elgureo et ai, 1995). Among these hydrogen-bonded crystals, proton transfer is detected only in cyclic hydrogen-bonded types [25-27]. 

In order to construct an organic hydrogen-bonded dielectric which operates under ambient conditions, one-dimensional hydrogen-bonded crystals have been explored. One of the successful examples is l,4-phenylenebis(squaric acid) (PBSQ) [44] (Takasu et al., 1996), in which two squaric acid moieties are connected by a p-phenylene unit. 

O—Distances in Hydrogen Bonded Crystals. The known O—distances in O—H- 0 bonds are listed in Table 9-III. The... 

A—H Distances in Hydrogen Bonded Crystals. There are a few scattered data for A—H B bonds where either A or B is not oxygen. Most of these cases were studied by proton magnetic resonance and, in some, proton-proton distances were determined rather than A—H distances. Table 9-IV shows the data available. 

Lifson, S. Hagler, A.T. Dauber, P. Consistent force field Studies of intermolecular forces in hydrogen-bonded crystals. J. Am. Chem. Soc. 1979,101 (18), 5111-5121. 

Pauling, L. The structure and entropy of ice and of other crystals with some randomness of atomic arrangement. J. Amer. Chem. Soc. 57,2680-2684(1935). Nagle, J. F. Lattice statistics of hydrogen bonded crystals. I. The residual entropy of ice. J. Math. Phys. 7, 1484-1491 (1966). 

Inelastic neutron scattering studies have shown [7-11] that many hydrogen-bonded crystals [potassium carbonate (i.e., KHCO3), various polyanilines, Ca(OH)2, and others] are characterized by the proton dynamics that is very decoupled from the backbone lattice. 

---