Chlorophenol, hydrogen bonding

Chlorophenol. hydrogen bonding, with A-4-thiazoline-2-thione. 377 Chloroplatinate anion, 121... 

The infrared absorption spectrum thus showB that o-chlorophenol in solution in carbon tetrachloride consists of about 91 percent cis molecules and 9 percent trans molecules. The cis molecules are more stable than the trans molecules by a standard free-energy difference of about 1.4 kcal/mole (calculated from the ratio of the areas of the peaks). This is presumably the difference in free energy of the cis molecule with its intramolecular hydrogen bond and the trans molecule with a weaker hydrogen bond with a solvent molecule. 

The weak hydrogen bond in o-chlorophenol stabilizes the gas molecule relative to those of the meta and para isomers, whereas the crystalline and liquid phases of the three substances, in which hydrogen bonds can be formed between adjacent molecules, have about the same stabil-... 

Figure 13 The pseudo-threefold screw arrangement of diol and p-chlorophenol molecules in the structure (ll)-(p-chlorophenol). Hydrogen atoms are omitted for clarity, and the hydrogen bonding is designated by dashed lines.

Protonation becomes a rapid reaction in protic solvents and in the presence of acids, as demonstrated for, e.g., -butyl acrylate in aqueous solution [207], methyl acrylate in EtOH [208], cinnamates in the presence of phenol in DMF [209], and benzaldehyde in ethanolic buffer solution [210]. Rate constants for protonation of aromatic radical anions (anthracene [211], naphthalene, 2-methoxynaphthalene, 2,3-dimethoxynaphthalene) by a number of proton donors including phenols, acetic acid, and benzoic acids in aprotic DMF were found to vary from 5.0 X 10 M- s-> (for anthracene, in the presence of p-chlorophenol) to 6.2 x lO s (for anthracene, in the presence of pentachlorophenol) [212]. For dimedone, PhOH, or PhC02H the rate of protonation depends on the hydrogen-bond basicity of the solvent and increases in the order DMSO < DMF MeCN [213],... 

Zaror [497] compared the uptakes of four phenols on a commercial activated carbon at a pH of 2 and reported both relatively low uptakes (<0.1 mmol/g at 0.3 mmol/L) and relatively small differences, in spite of the substantial differences in the nature of the substituents. Wang et al. [439] reported that the uptakes of p-nitrophenol, p-chlorophenol, and phenol were consistent with the notion that materials of high molecular weight are adsorbed to a more considerable extent than those of low molecular weight for compounds of similar chemical constitution Traube would be happy to learn that a century later [498] his rule lives on and that, under certain (perhaps very limited) conditions, the complexities discussed elsewhere in this review can be ignored. A clear example of the inapplicability of Traube s rule, however, is the study of Mostafa et al. [416] the authors did not attribute this to electrostatic effects or to changes in 7t- electron density (see below) but to the difference in the ability of hydrogen bond formation of the different phenols. ... 

Catalytic supercritical water oxidation is an important class of solid-catalyzed reaction that utilizes advantageous solution properties of supercritical water (dielectric constant, electrolytic conductance, dissociation constant, hydrogen bonding) as well as the superior transport properties of the supercritical medium (viscosity, heat capacity, diffusion coefficient, and density). The most commonly encountered oxidation reaction carried out in supercritical water is the oxidation of alcohols, acetic acid, ammonia, benzene, benzoic acid, butanol, chlorophenol, dichlorobenzene, phenol, 2-propanol (catalyzed by metal oxide catalysts such as CuO/ZnO, Ti02, MnOz, KMn04, V2O5, and Cr203), 2,4-dichlorophenol, methyl ethyl ketone, and pyridine (catalyzed by supported noble metal catalysts such as supported platinum). ... 

J. Han, Ri. Deming, and F.-M. Tao, Theoretical study of hydrogen-bonded complexes of chlorophenols with water or ammonia Correlations and predictions ofpK values, J. Phys. Chem. A 109 (2005), pp. 1159-1167. 

Radon forms a series of clathrate compounds (inclusion compounds) similar to those of argon, krypton, and xenon. These can be prepared by mixing trace amounts of radon with macro amounts of host substances and allowing the mixtures to crystallize. No chemical bonds are formed the radon is merely trapped in the lattice of surrounding atoms it therefore escapes when the host crystal melts or dissolves. Compounds prepared in this manner include radon hydrate, Rn 6H20 (Nikitin, 1936) radon-phenol clathrate, Rn 3C H 0H (Nikitin and Kovalskaya, 1952) radon-p-chlorophenol clathrate, Rn 3p-ClC H 0H (Nikitin and Ioffe, 1952) and radon-p-cresol clathrate, Rn bp-CH C H OH (Trofimov and Kazankin, 1966). Radon has also been reported to co-crystallize with sulfur dioxide, carbon dioxide, hydrogen chloride, and hydrogen sulfide (Nikitin, 1939). 

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