Monochlorination products are compounds formed by the replacement of one hydrogen atom in a hydrocarbon or other compound with a chlorine atom. Monochlorination reactions are typically carried out using chlorine gas or other chlorinating agents, such as hypochlorous acid or sulfuryl chloride. The reaction conditions and the structure of the starting material determine the regioselectivity and stereoselectivity of the reaction.

For example, the monochlorination of ethane can produce either ethyl chloride or chloroethane, depending on the reaction conditions. The free radical chlorination of ethane typically produces a mixture of both products, while the electrophilic chlorination of ethane using hydrogen chloride and a Lewis acid catalyst selectively produces chloroethane.

The monochlorination of alkenes can produce either mono- or di-substituted products, depending on the reaction conditions. The addition of chlorine to an alkene typically occurs via a concerted mechanism, with the formation of a three-membered chloronium ion intermediate. The regioselectivity of the reaction is determined by the stability of the intermediate chloronium ion, which is influenced by the electronic and steric effects of the substituents on the alkene.

The monochlorination of aromatic compounds typically occurs via an electrophilic aromatic substitution mechanism. The reaction involves the addition of a chlorine electrophile to the aromatic ring, followed by the loss of a proton. The regioselectivity of the reaction is determined by the electronic effects of the substituents on the aromatic ring, which influence the stability of the intermediate carbocation.

Overall, monochlorination reactions are powerful tools for the synthesis of a wide range of chlorinated compounds. The variety of reaction conditions and the different reactivities of hydrocarbons and other compounds allow for the selective introduction of chlorine atoms into specific positions of a molecule.