Monohydrate hydrogen bonding

In the structure of triphenylselenonium chloride monohydrate, hydrogen bonds participate in addition to secondary bonds and electrostatic interactions between Ph3Se cations and CP anions. ... 

Fig. 13. drawing of the crystal structure of guanine hydrochloride monohydrate. Hydrogen bonds are indicated by dashed lines. 

Flensburg, C., Larsen, S. and Stewart, R.F. (1995) Experimental charge density study ofmethylam-monium hydrogen succinate monohydrate. A salt with a very short O-H-O hydrogen bond,. /. Phys. Chem., 99, 10130-10141. 

Grant and coworkers [8] studied the dehydration kinetics of piroxicam monohydrate using both model-free and model-fitting approaches in an effort to understand the effects of lattice energy and crystal structure. The dehydration kinetics was found to differ when determined under isothermal and nonisothermal conditions. Ultimately, the dehydration behavior of piroxicam monohydrate was determined by details of the crystal structure, which was characterized by an absence of channels and a complicated hydrogen-bonding network, and ab initio calculations proved useful in understanding the structural ramifications of the dehydration process. 

Fluconazole was shown to be crystallizable in the form of a monohydrate and as a 1/4 ethyl acetate solvate, as well as a new nonsolvated form [56], In the hydrate phase the water molecules were established as isolated sites, while the ethyl acetate molecules occupied constricted channels in its phase. In all of the structures, the fluconazole molecule adopted a common overall conformation, but one that was capable of some degree of flexibility. Hydrogen-bonding effects were deduced to be dominant in determining the structure of the different solvatomorphs. 

Methoxypurine was found to crystallize as a hemihydrate from /V,/V -dimethyl formamide, and as a trihydrate from water [63]. Thermal treatment of the trihydrate could be used to obtain the hemihydrate. Zafirlukast was obtained in the form of monohydrate, methanol, and ethanol solvatomorphs, with the drug substance adopting a similar conformation in all three structures [64], In the isostructural methanol and ethanol solvates, the solvent molecules are hydrogen-bonded to two zafirlukast molecules, while in the monohydrate, the water molecules are hydrogen-bonded to three zafirlukast molecules. The structures of the acetone and isopropanol solvatomorphs of brucine have been reported, where the solvent controlled the self-assembly of brucine on the basis of common donor-acceptor properties [65],... 

Figure 3. Schematic diagram of the hydrogen-bond structure of p-maltose monohydrate (MALTOS11). The anrows indicate infinite chains. Distances and angles are from the neutron diffraction analysis.

Two recent studies show that this conclusion does not apply to very short hydrogen bonds. In methylammonium hydrogen succinate monohydrate, three normal hydrogen bonds, with O—H between 1.72 and 1.86 A exist, while a very... 

Fig. 13. Monensin monohydrate (after (76)). Hydrogen bonds are shown by broken lines with the postulated positions for the hydrogen atoms.

A, and the O H -0 length 2.53 A. The 2,6-dicarboxylic acid monohydrate exists in the neutral form, while the 3,5-isomer, dinicotinic acid, exists in the intermediate form, but here each molecule is joined by two kinds of hydrogen bond (O—H- O, 2.59 A O H- -N, 2.52 A) to four surrounding molecules. Pyridine-2,3-dicarboxylic acid exists in the zwitterionic form (38), as does cinchomeronic acid, the 3,4-dicarboxylic isomer (39), the N—H bond distances being 0.89 A and 1.09 A respectively. 

A neutron-diffraction study of /3-maltose monohydrate provided a more defined description of the hydrogen bonding present in the molecule.16 With the exception of the intramolecular bond, 0-2 -H------------... 

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