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Halogenation of saturated hydrocarbons is a substitution reaction. The reaction typically involves free radical pathways. The regiochemistry of the halogenation of alkanes is largely determined by the relative weakness of the C–H bonds. This trend is reflected by the faster reaction at tertiary and secondary positions.
For example, consider radical bromination of toluene: [5] bromination of toluene with hydrobromic acid and hydrogen peroxide in water. This reaction takes place on water instead of an organic solvent and the bromine is obtained from oxidation of hydrobromic acid with hydrogen peroxide. An incandescent light bulb suffices to radicalize.
In organic chemistry, an electrophilic aromatic halogenation is a type of electrophilic aromatic substitution. This organic reaction is typical of aromatic compounds and a very useful method for adding substituents to an aromatic system.
An example is the conversion of alkyl chloride into alkyl fluoride: C 3 H 5-Cl + NaF → R-F + NaCl. This kind of reaction is called Finkelstein reaction. [2] However, it is also possible, for example, to produce phosphorus fluoride compounds by transhalogenating chlorine, bromine or iodine bound to phosphorus with a metal fluoride. [3]
Regiochemistry follows from the reaction mechanism, which exhibits halogen attack on the least-hindered unsaturated carbon. The mechanism for this chain reaction resembles free radical halogenation, in which the peroxide promotes formation of the bromine radical. However, this process is restricted to addition of HBr.
Related to their easy oxidation, the methyl groups are susceptible to halogenation. When treated with elemental bromine , these groups are brominated, yielding xylylene dibromide : [ 8 ] C 6 H 4 (CH 3 ) 2 + 2 Br 2 → C 6 H 4 (CH 2 Br) 2 + 2 HBr
Research has found that using a mix of water—along with fruit and vegetable sanitizers that contain peroxyacetic acid and hydrogen peroxide—can help reduce levels of norovirus and hepatitis A ...
For alkylbenzene derivatives, e.g. toluene, the alkyl positions tend to be halogenated by free radical conditions, whereas ring halogenation is favored in the presence of Lewis acids. [6] The decolouration of bromine water by electron-rich arenes is used in the bromine test. Reaction between benzene and halogen to form an halogenobenzene