Oxygen hydrogen bonded

However, because of the high temperature nature of this class of peroxides (10-h half-life temperatures of 133—172°C) and their extreme sensitivities to radical-induced decompositions and transition-metal activation, hydroperoxides have very limited utiUty as thermal initiators. The oxygen—hydrogen bond in hydroperoxides is weak (368-377 kJ/mol (88.0-90.1 kcal/mol) BDE) andis susceptible to attack by higher energy radicals ... 

Bond dissociation energies (BDEs) for the oxygen—oxygen and oxygen— hydrogen bonds are 167—184 kj/mol (40.0—44.0 kcal/mol) and 375 kj/mol (89.6 kcal/mol), respectively (10,45). Heats of formation, entropies, andheat capacities of hydroperoxides have been summarized (9). Hydroperoxides exist as hydrogen-bonded dimers in nonpolar solvents and readily form hydrogen-bonded associations with ethers, alcohols, amines, ketones, sulfoxides, and carboxyhc acids (46). Other physical properties of hydroperoxides have been reported (46). 

The second route for ether formation is initiated by protonation of the carbene followed by capture of the cation with alcohol (8). Finally a concerted insertion into the oxygen-hydrogen bond of the alcohol (8) has been considered, but there is no experimental support for this path. The... 

To atomize the phenol molecule, we have to cleave six carbon-carbon bonds in the aromatic ring (Cb-Cb), five carbon-hydrogen bonds (Cb-H), one carbon-oxygen bond (Cb—O), and one oxygen-hydrogen bond (O-H). The symbol El has been adopted is this equation (instead of the more used symbol E) to avoid confusion with the quantities discussed in the previous section. 

A systematic study on enzymatic catalysis has revealed that isolated enzymes, from baker s yeast or old yellow enzyme (OYE) termed nitroalkene reductase, can efficiently catalyze the NADPH-linked reduction of nitroalkenes. Eor the OYE-catalyzed reduction of nitrocyclohexene, a catalytic mechanism was proposed in which the nitrocyclohexene is activated by nitro-oxygen hydrogen bonds to the enzymes His-191 and Asn-194 [167, 168]. Inspired by this study Schreiner et al. 

Stepwise, but heterolytic, mechanisms have been suggested in the insertion of carbenes into oxygen-hydrogen bonds. The reactivity of water and halide ions towards dihalomethylenes parallels their reactivity in Sn2 displacements (Hine and Dowell, 1954), suggesting that an electrophilic carbene attacks water initially by way of the non-bonded electron pair on oxygen giving an ylid (equation 21). An analogous mechanism could be followed in the insertion of carbenes into the... 

The carbonylation of alcohols can proceed with formation of carboxylic acid by catalytic insertion of CO into the carbon-oxygen bond. An alternative reaction gives rise to oxalate or formate esters, when the CO is inserted into the oxygen-hydrogen bond. The members of the nickel triad carbonylate alcohols to give each of these products, and they will be discussed separately. 

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