Carbon-halogen bond, reaction number

The second technique of CRP is ATRP first described by Wang and Matyjaszewski [38] and by Sawamoto and co-workers [39]. This technique, since reviewed in a number of monographies and feature articles [22,40-42] involves the reversible homolytic cleavage of a carbon-halogen bond by a redox reaction between the organic halide and a copper halide (in the presence of a ligand, e.g. bipyridine) which yields the initiating radical and the oxidized copper complex ... 

The nonbonding electron clouds of the attached fluorine atoms tend to repel the oncoming fluorine molecules as they approach the carbon skeleton. This reduces the number of effective coUisions, making it possible to increase the total number of coUisions and stiU not accelerate the reaction rate as the reaction proceeds toward completion. This protective sheath of fluorine atoms provides the inertness of Teflon and other fluorocarbons. It also explains the fact that greater success in direct fluorination processes has been reported when the hydrocarbon to be fluorinated had already been partiaUy fluorinated by some other process or was prechlorinated, ie, the protective sheath of halogens reduced the number of reactive coUisions and aUowed reactions to occur without excessive cleavage of carbon—carbon bonds or mnaway exothermic processes. 

Elementary fluorine or chlorine may act drastically on a number of covalent compounds, forming products in which the only bonds remaining are eiement-to-halogen bonds. Such reactions are called halogenolyses the chlorinolysis of carbon diselenide and the fluorinolysis of ethane are typical ... 

Oxidation is coupled with reduction A reducing agent is oxidized and an oxidizing agent is reduced. For reactions in which oxidation or reduction has taken place on carbon, if the reaction inaeases the number of C—H bonds or decreases the number of C—O, C—N, or C—X bonds (where X d notes a halogen), the compound has been reduced if the reaction decreases the number of C—H bonds or increases the number of C—O, C — N, or C—X bonds, the compound has been oxidized. Similarly, the number of N—H or S—H bonds inaeases in reduction reactions, and the number of N—O or S—O bonds increases in oxidation reactions. The oxidation state of a carbon atom equals the total number of its C—O, C—N, andC — Xbonds. 

Electrophilic addition of a hydrogen halide to an alkene is the addition of a halogen (Cl, Br, or I) and H across the carbon-carbon double bond. The reaction occurs with Markovnikov regioselectivity with the H adding to the carbon with the greater number of hydrogens. 

As a general rule, and as shown in the fifth example in Table 6.7, bromine (Br2) and chlorine (CI2) in, for example, carbon tetrachloride (tetrachloromethane, CCI4) solution, add across the carbon-carbon triple bond to give tram- [antarafacial, and-, or ( )] dibromoalkene. Also, as a general rule (albeit with a very limited number of comparisons), these addition reactions occur more slowly with alkynes than they do with alkenes and a second equivalent of halogen can add to produce the tetra-halide (Equation 6.68). 

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