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The reaction mechanism for chlorination of benzene is the same as bromination of benzene. Iron(III) bromide and iron(III) chloride become inactivated if they react with water, including moisture in the air. Therefore, they are generated by adding iron filings to bromine or chlorine. Here is the mechanism of this reaction:
Addition of Cl 2 destroys the aromaticity of the benzene ring, and the addition of two more Cl 2 molecules is rapid compared to the first. Hence, only thrice-dichlorinated product can be isolated from this reaction. Radical addition: C 6 H 6 + 3Cl 2 → C 6 H 6 Cl 6. Hexachlorocyclohexane isomers with more than one chlorine atom per carbon are:
The nitration of benzene is achieved via the action of the nitronium ion as the electrophile. The sulfonation with fuming sulfuric acid gives benzenesulfonic acid. Aromatic halogenation with bromine, chlorine, or iodine gives the corresponding aryl halides. This reaction is typically catalyzed by the corresponding iron or aluminum trihalide.
Photochlorination is a chlorination reaction that is initiated by light. Usually a C-H bond is converted to a C-Cl bond. Photochlorination is carried out on an industrial scale. The process is exothermic and proceeds as a chain reaction initiated by the homolytic cleavage of molecular chlorine into chlorine radicals by ultraviolet radiation ...
However, the extent of chlorination is difficult to control. Aryl chlorides may be prepared by the Friedel-Crafts halogenation, using chlorine and a Lewis acid catalyst. [2] The haloform reaction, using chlorine and sodium hydroxide, is also able to generate alkyl halides from methyl ketones, and related compounds. Chloroform was formerly ...
The chain mechanism is as follows, using the chlorination of methane as an example: Initiation Ultraviolet radiation splits a chlorine molecule to two chlorine atom radicals. Methane chlorination: initiation Chain propagation (two steps) A radical abstracts a hydrogen atom from methane, leaving a primary methyl radical.
Benzene can be readily converted to chlorobenzene by nucleophilic aromatic substitution via a benzyne intermediate. [1] Chlorobenzene is treated with aqueous sodium hydroxide at 350 °C and 300 bar or molten sodium hydroxide at 350 °C to convert it to sodium phenoxide, which yields phenol upon acidification. [2]
The LD50 (oral, rats) is 756 mg/kg. Animal studies have shown that 1,2,4-trichlorobenzene affects the liver and kidney, and is possibly a teratogen. [4] There is no regulated occupational exposure limit for chemical exposure, but the National Institute for Occupational Safety and Health recommends no greater exposure than 5 ppm, over an 8-hour workday.