Hydrogen bond probability

Three dimensional X-ray diffraction data point to a largely planar structure in all of the molecules studied this ensures optimum conjugation (overlapping of the TT-electrons). Intramolecular hydrogen bonds probably contribute considerably towards supporting the planar conformation. 

The general order of cis effect seems to be (H20)4> (NH3)4 eu2 (DMG)2 corrin (CN)4. Comparison between (NH3)4 and (H20)4 is important since no complications arise due to any difference in charge, and in addition the regular change observed as H2O is replaced by NH3 (Section II, D) indicates that differences in hydrogen bonding probably play no part. 

Exclusively strong hydrogen bond, probably the strongest detected up to date between two neutral molecules, is formed in a polar solution between FH and... 

When this theory was used to predict the solubility of polymers in a variety of solvents, it was only partially successful. It was apparent that other intermolecular forces were at work which could not be calculated by this simple procedure. Hydrogen bonding, probably the strongest type of intermolecular force in a nonelectrolyte, was the clue for making solubility parameter theory work. 

In all Type A crystals, the hydrogen bond has a symmetrical potential-energy curve. In many acid salts, with open structures, the O- -H- -O distance in the double-anion, R COgHO C R, is close to 2.44 A. In a smaller number of chelated, but otherwise similar, structures, the 0- H - 0 distance is somewhat shorter and there are stereochemical reasons for this. For the latter cases, the hydrogen bond probably is genuinely symmetrical, with a single-well potential. Some, at least, of the open Type A structures may also contain symmetrical 0---H---0 bonds. 

The appearance of slow and fast sedimentation peaks at a narrower interval of pH (ApH=0.2) change is the result of PEC particle destruction into the individual macromolecules. The structure of PEC composed of polyampholyte and polyelectrolyte can be represented as double-strand sequences of pairs formed with the help of cooperative systems of ionic and hydrogen bonds. Probably near the lEP, some acidic and basic groups of polyampholytes displaced on loops begin to interact with each other cooperatively with the formation of intramolecular complexes. The mechanism of PEC destruction can be represented as follows ... 

The value of AT (>10 Lmor ) and the independence of Wj from [ROOH] indicate that near the surface of the heterogeneous metal-polymer catalyst the local concentration of hydroperoxide is high. It has been shown that in the vicinity of catalytic centers there are always vacant carboxyl groups able to bind ROOH molecules by hydrogen bonds. Probably, the transfer of ROOH molecules to the active center is carried out initially via their migration across the two-dimensional catalyst surface, and only after their decay do the radicals formed escape into the bulk liquid where the chain radical oxidation of hexene takes place. 

Hydroxy heterocycles, such as hydroxyquinolines 81, 2-hydroxy-3-nitropyridine, or 4-hydroxypyrimidines 82, promote Passerini-Smiles couplings in good to moderate yields rScheme 19.441. In these cases, hydrogen bonding probably develops to favor the whole... 

Hydrogen bonds probably contribute to the attachment of postage stamps to envelopes where the adhesive (polyvinyl alcohol) and paper (cellulose fibres) both contain -OH groups. Wood is also rich in cellulose and the reactive adhesives based on formaldehyde contain hydroxyl or amine groups capable of participating in hydrogen bonds. 

Bigelow (1960) had previously interpreted his ultraviolet difference spectra measurements in terms of hydrophobic bonding, and had indicated that a tyrosyl-carboxyl hydrogen bond probably does not exist. However, Bigelow s measurements were made at 25°C. therefore, he could not detect the effect of the hydrogen bond since the latter manifests itself most clearly at low temperature (transformation II to III of Fig. 167). 

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