Intra- and inter-molecular hydrogen bonds

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

DSC studies have shown that modification alters thermal transition temperatures and the overall enthalpy (AHgei) associated with gelatinization (Tables 10.13 and 10.14). Upon hydroxypropylation, the reactive groups introduced into the starch chains are capable of disrupting the inter-and intra-molecular hydrogen bonds, leading to an increase in accessibility by water that lowers... 

On occasions it is desirable to investigate the spectroscopic properties of solutions at high dilution (i.e. 0.005 m), as for example in the study of inter- and intra-molecular hydrogen bonding of compounds containing hydroxyl groups. 

Some enamines have been shown to form inter- and intra-molecular hydrogen bonds in the solid state77. Thus, a-tetrahydropyrrolidinylidene-2 (44) and ethyl a-hexahydroaze-pirylidene acetate (45) have been shown to occur as / -enaminoesters of configuration Z in the solid state, i.e. the same configuration as they have in solution78. 

N-H and C=0 stretching modes in the IR spectrum may be used to infer the inter- and intra-molecular hydrogen bonding pattern [4], for example between polymorphs [28, 29], IR may also be used to study the hydrogen bonding within hydrates as described in Section 6.3.2. 

The crystallization behaviour of polysaccharides is Influenced not only by their chain conformation but also by the multiple possibilities of inter and intra molecular hydrogen bonding (1,2). This multiplicity, in particular, e g>lains why several polymorphic forms can be obtained when different crystallization conditions are selected for a given specimen. 

This binding between cholesterol and azone results in a more disordered state, which suggests that the cholesterol molecules are extracted from the lamellae of the SC. The addition of azone to propylene glycol increases the solubility of cholesterol. Thus, the complex formed between azone and cholesterol dissolves into propylene glycol more easily than that of ceramide-3 and azone, with this dissolution attributed to inter- and intra-molecular hydrogen bonding. 

The three main active functional groups of chitosan include an amino/acetamido group and both primary and secondary hydroxyl groups at the C2, C3, and C6 positions, respectively. Easy generation of both inter- and intra-molecular hydrogen bonds, which causes variation in their structures and physicochemical properties is mainly associated with the amount of amino contents... 

Cellulose is insoluble in water and common organic solvents, and cannot melt because of strong inter- and intra-molecular hydrogen bonds caused by the abundant content of hydroxyl groups and the stereoregularity of the cellulose chains (Fig. 1). Therefore, it is difficult to produce cellulose articles by solution or melting processes [23]. Recently, Lindman and coworkers pointed out that cellulose is significantly amphiphilic and hydrophobic interactions may be important in... 

N-alkylated residue, and in particular N-methylation is an important modification of the peptide bond that influence the conformational freedom of the peptide backbone. The steric constraints introduced by the N-alkyl group have also effect on the side chain freedom of the neighboring amino acids. Additionally, the number of inter- and intra-molecular hydrogen bonds decreases due to the removal of the backbone NH groups, destabilizing both a-helix and P-sheet conformations. Finally, the attached carbonyl group shows an increased basicity and decreased polarity. 

Carbohydrate (polyol) sweeteners are of great importance for nutritional reasons and because of their good taste quality. Because of the structural nature of these compounds, the inter- and intra-molecular hydrogen bonds are thought to play important roles in their activities. MD simulations in water have been carried out by Birch and co-workers in an attempt to define the SAR of some polyols. They studied sweet a-mannopyranose, its bitter anomer S-D-mannopyranose, and some related polyols. The radial distribution functions of these compounds show different and distinctive behaviors... 

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