Molecular hydrogen bond

Solubility in Water. Alkyl halides and alcohols differ markedly from one another in their solubility in water. All alkyl halides are insoluble in water, but low-molecular-weight alcohols (methyl, ethyl, n-propyl, and isopropyl) are soluble in water in all proportions. Their ability to participate in inter-molecular- hydrogen bonding not only affects the boiling points of alcohols, but also enhances their water solubility. Flydrogen-bonded networks of the type shown in Figure 4.5, in which alcohol and water molecules associate with one another, replace the alcohol-alcohol and water-water hydrogen-bonded networks present in the pure substances. 

The structure of malonyl-a-aminopyridine (cf. 121) has been discussed by Snyder and Robinson/ who interpreted the infrared and ultraviolet spectra and the fact that it could be converted into a monochloro derivative (122, R = Cl) to indicate that the intra-molecularly hydrogen-bonded hydroxy form 122 (R = OH) was predominant. However, comparison of the basicities of the methoxy compound 122 (R = OMe), the mesomeric betaine 123 (R = Me), and the parent compound indicates that in aqueous solution the last exists mainly in the zwitterion form 123 (R = H), ... 

Accurate X-ray crystallographic data indicate that 5-hydrazino-3-mercapto-1,2,4-triazole exists in the solid state as a betaine, either as 165 or 166, with strong inter molecular hydrogen bonding occurring be-... 

Here the favorable geometrical arrangement with two hydrogen bonds contributes 14 kcal to the stability of the hydrogen bonded product, (7). These are called inter-molecular hydrogen bonds (inter means between). 

The basic requirement for cellulose dissolution is that the solvent is capable of interacting with the hydroxyl groups of the AGU, so as to eliminate, at least partially, the strong inter-molecular hydrogen-bonding between the polymer chains. There are two basic schemes for cellulose dissolution (i) Where it results from physical interactions between cellulose and the solvent (ii) where it is achieved via a chemical reaction, leading to covalent bond formation derivatizing solvents . Both routes are addressed in details below. 

Fig. 2 Schematic representation of cellulose structures in solution Part A shows the fringed micellar structure. Parts B and C show possible chain conformations of celluloses of different DP. For high molecular weight cellulose, C, intra-molecular hydrogen bonding is possible...

Rey, S., Caron, G., Ermondi, G., Gaillard, P., Pagliara, A., Carrupt, P. A., Testa, B. Development of molecular hydrogen bonding potentials (MHBPs) and their application to structure-permeation... 

The absorption spectrum of TIN in methylcyclo-hexane/isopentane at 150 K is represented by curve I, Fig. k. Curve III shows the absorption spectrum of MT in hexane at 296 K. In unpolar solvents the intra-molecular hydrogen bond of TIN is still intact (curve... 

I) whereas in polar solvents at least part of the TIN molecules change this intramolecular into an inter-molecular hydrogen bond to solvent molecules (curve... 

II). From this it must be concluded that the long-wavelength absorption of curve I is due to the intra-molecular hydrogen bond of TIN in unpolar solvents as the intensity of this band is reduced in polar solvents (curve II) and disappears completely in the spectrum of MT (without intramolecular hydrogen bond), curve III. Curve IVa represents the fluorescence and IVb the phosphorescence emission of both TIN and MT in... 

A protein s secondary structure arises from the formation of intra- and inter-molecular hydrogen bonds. All carboxyl group oxygens and amine hydrogens of a polypeptide participate in H-bonding. Protein secondary structure also derives from the fact that although all C-N bonds in peptides have some double bond character and cannot rotate, rotation about the Co-N and Ca-C bonds is possible and is... 

The phosphonic acids, much like arsonic acid, are weak dibasic acids. In non-polar solvents, phosphonic acids associate with long chains through molecular hydrogen bonding. 

PI Z = 1 Dn = 1.475 R = 0.05 for 961 neutron intensities. This is a neutron-diffraction refinement of a structure previously determined by X-ray diffraction.56 All of the hydroxyl groups are involved in inter-molecular hydrogen-bonds which form infinite chains, with H O distances ranging from 175.5 to 200.2 pm, and O-H O angles... 

Figure 4.3 Inter- and intra-molecular hydrogen bonds of native cellulose.

The principle of the method is that once a substance crystallizes, the interconversion of the various conformers stops and so the crystals correspond to one discrete conformation or another. This has established, that 1,2-dichloroethane crystallises exclusively in the anti form, while ethylene chlorohydrin crystallizes in a gauche form because of intra molecular hydrogen bonding. But when the molecule crystallizes in two or more conformations, we say that it shows polymorphism. 

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