Phenols hydrogen-bond formation mechanism

Hydration has also been recorded by Fischer and Wan , who reported that the phenol derivatives 18, 19 and 20 undergo addition of water to the double bond when they are irradiated in acetonitrile/water. The study has shown that the proposed mechanism of m-quinonemethide (see later for further discussion of quinonemethides) formation probably involves a solvent-mediated proton transfer of the phenolic hydrogen to the -carbon of the alkene moiety. This must occur with the participation of a so-called water trimer. This yields the zwitterion 21 that is responsible for the formation of the products, e.g. 22 from 18. The reactions are efficient with quantum yield values of 0.1-0.24. 

Adsorption of SOC by activated carbon may involve various combinations of chemical, electrostatic, and physical (i.e. non-specific dispersion forces) interactions [59]. The overall adsorption interactions can be very complex for some SOCs. One good example is the adsorption of phenolic compounds, probably the most widely studied class of adsorbates in the activated carbon literature. Several possible mechanisms have been proposed for phenol adsorption [60-69]. These incluile (i) n-n dispersion interactions between the basal plane of activated carbon and the aromatic ring of the adsorbate, (ii) electrostatic attraction-repulsion interactions, (iii) hydrogen bonding between adsorbate and surface functional groups of activated carbons, (iv) electron acceptor-donor complex formation mechanisms between the carbonyl... 

The use and importance of aromatic compounds in fuels sharply contrasts the limited kinetic data available in the literature, regarding their combustion kinetics and reaction pathways. A number of experimental and modelling studies on benzene [153, 154, 155, 156, 157, 158], toluene [159, 160] and phenol [161] oxidation exist in the literature, but it would still be helpful to have more data on initial product and species concentration profiles to understand or evaluate important reaction paths and to validate detailed mechanisms. The above studies show that phenyl and phenoxy radicals are key intermediates in the gas phase thermal oxidation of aromatics. The formation of the phenyl radical usually involves abstraction of a strong (111 to 114 kcal mof ) aromatic—H bond by the radical pool. These abstraction reactions are often endothermic and usually involve a 6 - 8 kcal mol barrier above the endothermicity but they still occur readily under moderate or high temperature combustion or pyrolysis conditions. The phenoxy radical in aromatic oxidation can result from an exothermic process involving several steps, (i) formation of phenol by OH addition to the aromatic ring with subsequent H or R elimination from the addition site [162] (ii) the phenoxy radical is then easily formed via abstraction of the weak (ca. 86 kcal moT ) phenolic hydrogen atom. 

The fact that divalent metal ions, the vanadyl ion, and their chelates, do not catalyze the hydrolysis forms [Ll and [IV] to an appreciable extent is in accord with the proposed mechanism, since coordination of the phosphate group by the metal ion would be prevented or greatly reduced by the presence of two protons. Accordingly metal ion catalysis by Cu and VO ions increases in effectiveness as the number of protons on the substrate is successively reduced. Such behavior would not be expected if transfer of a hydrogen-bonded proton from the carboxyl group to the phenolic ester oxygen were the only pathway for the reaction. Metal ion catalysis of the hydrolysis of [V], [VI],. and [VII] was not measured because of the formation of a solid phase in the presence of Cu and VO ions. 

POLYAMIDE. Separations are based on formation of hydrogen bonds between the functional groups of the sample (phenols, amino acid derivatives, heterocyclic nitrogen compounds, carboxylic and sulfonic acids) and the carbonyl oxygen of the amide group, as well as a general reversed-phase partition mechanism (water is the weakest solvent). Available as two polycondensation products, polyundecanamide (PA 11) and polycaprolactam (PA 11). 

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