Hydrogen-bonding interations

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). 

Polymer Adsorption. The driving force for adsorption typically is the en-thalpic interaction between the interface and the polymer segments. Exceptions include aqueous solutions near hydrophobic substrates. In that case, the driving force may include the hydrophobic interaction between water and the surface. The enthalpic interactions may be of various forms such as hydrogen bonding, inter-facial tension, van der Waals attraction, polar interactions, and electrostatic attractions. This enthalpic interaction is offset by the loss in conformational entropy... 

Stabilization of a columnar phase for a calix[4]arene by a hydrogen bonding inter-... 

Many biological processes involve an associa tion between two species in a step prior to some subsequent transformation This asso ciation can take many forms It can be a weak associ ation of the attractive van der Waals type or a stronger interaction such as a hydrogen bond It can be an electrostatic attraction between a positively charged atom of one molecule and a negatively charged atom of another Covalent bond formation between two species of complementary chemical re activity represents an extreme kind of association It often occurs in biological processes in which aide hydes or ketones react with amines via imine inter mediates... 

These types of polar monomer provide sites for hydrogen bonding which increase the cohesive strength of the PSA because of strong inter-chain interaction, and they can also allow for hydrogen bonding or other polar interactions with some substrates. 

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. 

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-... 

Acrylamide can form inter- and intramolecular hydrogen bonds. The reactivities of acrylamide are af-... 

Dielectric measurements were used to evaluate the degrees of inter- and intramolecular hydrogen bonding in novolac resins.39 The frequency dependence of complex permittivity (s ) within a relaxation region can be described with a Havriliak and Negami function (HN function) ... 

B Critical temperature increases with the strength of inter-molecular forces. For example, CH4 cannot form hydrogen bonds so it has a lower critical temperature than either NHS or H20, which can form hydrogen bonds. 

In general the A—H B hydrogen bond can be taken to be approximately linear for example, in diaspore the angle between the inter-... 

Thus, because of the acetamido groups, there are more intra- and inter-chain hydrogen bonds in 3 and 4 than in 1 and 2. Because of the polarity problem, the chitin I— II transition is also irreversible, as in the case of cellulose. 

Fic. 10.—Parallel packing arrangement of 6-fold, A-amylose (8) molecules, (a) A stereo side view of less than 2 turns of a pair of double helices 10.62 A (=al2) apart. The two strands in each helix are distinguished by open and filled bonds, and the helix axis is also drawn, for convenience. Note that atom 0-6 mediates both intra- and inter-double helix hydrogen bonds. 

Fig. 14.—Antiparallel packing arrangement of extended, 4-fold, 2,3,6-tri-O-ethylamylose (12) helices, (a) Stereo view of two unit cells approximately normal to the lie-plane. The helix at the center (filled bonds) is antiparallel to the two helices (open bonds) at the comers in the back. There is no intra- or inter-chain hydrogen bond, and only van der Waals forces stabilize the helices, (b) A e-axis projection of the unit cell shows that the ethyl groups extend into the medium in radial directions. 

Fig. 30. — Packing arrangement of 4-fold antiparallel double helices of potassium hyaluronate (32). (a) Stereo view of a unit cell approximately normal to the line of separation of the two helices. The two chains in each duplex, drawn in open and filled bonds for distinction, are linked by not only direct hydrogen bonds, but also water bridges. Inter double-helix hydrogen bonds are mediated between hydroxymethyl and iV-acetyl groups. Potassium ions (crossed circles) at special positions have only a passive role in the association of hyaluronate chains.

Fig. 35.—(a) Stereo view of about a turn of the 3-fold double helix of potassium gellan (41). The two chains are drawn in open and filled bonds for distinction. Both intra- and inter-chain hydrogen bonds stabilize the helix. The vertical line is the helix axis. Octahedrally coordinated potassium ions (crossed circles) and triply hydrogen-bonded water molecules (open circles) located above the ions are integral components of the structure of 41. 

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