Carbon-hydrogen bond cleavag

The greater ease of reaction compared to nitrosodeprotonation may arise from the greater ease of carbon-carbon bond cleavage compared to carbon-hydrogen bond cleavage for in the latter reaction this is partly rate-determining and may so be in the decarboxylation as well. 

The large isotope effect suggested that carbon-hydrogen bond cleavage occurs via a linear and symmetrical transition state, while the loss of stereochemical integrity via epimerization suggested the involvement of an intermediate. A mechanism that is consistent... 

Baciocchi E, Bietti M, Putignani L, Steenken S (1996) Side-chain fragmentation of arylalkanol radical cations. Carbon-carbon and carbon-hydrogen bond cleavage and the role of a- and p-OH groups. J Am Chem Soc 118 5952-5960... 

This established C-H chemistry in molecular coordination compounds should have its formal analog in metal surface chemistry. Carbon-hydrogen bond-cleavage is a common reaction at metal surfaces but it does not comprise mechanistically the simple collision of a hydrocarbon such as methane with a metal surface vide infra). Methane neither reacts with nor is chemisorbed on a metal surface under moderate conditions. However, propylene does chemisorb, and then C-H bonds may be broken, depending upon the nature of the metal surface. Generally, the sequence at the surface comprises first the formation of a coordinate bond between a surface metal atom(s) and some functionality in the... 

A subsequent study ° from the Arnold group showed an intriguing stereoelectronic effect in oxidative benzylic carbon-hydrogen bond cleavage reactions of substrates 8 and 9 (Scheme 3.7). In this study, electron transfer reactions were conducted in the presence of a nonnucleophilic base. Radical cation formation also weakens benzylic carbon-hydrogen bonds, thereby enhancing their acidity. Deprotonation of benzylic hydrogens yields benzylic radicals that can be reduced by the radical anion of dicyanobenzene to form benzylic anions that will be protonated by solvent. This sequence of oxidation, deprotonation, reduction, and protonation provides a sequence by which epimerization can be effected at the benzylic center. In this study, tram isomer 10 showed no propensity to isomerize to cis isomer 11 (equation 1 in Scheme 3.7), but 11 readily converted to 10 (equation 2 in Scheme 3.7). The reactions were repeated in deuterated solvents to assure that these observations resulted from kinetic rather than thermodynamic factors. Trans isomer 9 showed no incorporation of deuterium (equation 3 in Scheme 3.7) whereas cis isomer 11 showed complete deuterium incorporation. The authors attributed this difference in reactivity to... 

Awachie, P. I., Agwada, V. C. Evidence for rate limiting carbon-hydrogen bond cleavage in the Leuckart reaction. Tetrahedron 1990,46, 1899-1910. 

Figure 8.6 Carbon-hydrogen bond cleavage in ethers, amines and aldehydes.

Kakiuchi F, Matsuura Y, Kan S, Chatani N (2005) A RuH2(CO)(PPh3)3-catalyzed regioselective arylation of aromatic ketones with arylboronates via carbon-hydrogen bond cleavage. 1 Am Chem Soc 127 5936-5945... 

The RiiH2(CO)(PPh3)3-CATALYSED ALKYLATION, ALKENYLATTON AND ARYLATION OL AROMATIC KETONES VIA CARBON-HYDROGEN BOND CLEAVAGE... 

Another example of reactions with carbon-hydrogen bond cleavage is shown by acetylene complexes 13 13aR... 

Several kinetic models for photocatalytic processes have been proposed. One of the possible reaction paths for the initiation of the degradation reaction of several hydrocarbon compounds appears to be an oxidative carbon-hydrogen bond cleavage by hydroxyl radicals attack. Hydroxyl radicals are generated as a consequence of electron transfer to the semiconductor holes by adsorbed hydroxyl ions or water molecules (Turchi and Ollis, 1990). 

Carbon-Hydrogen Bond Cleavage by Electrophilic Metals... 

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