Study GuideOrganic Chemistry I–Reactions of Alkanes1.Alkanes: HalogenationAlkanes can react withhalogens(such as chlorine or bromine) whenultraviolet (UV) light or heatispresent. This reaction produces ahaloalkane(also called analkyl halide).A common example is thechlorination of methane.When Does the Reaction Occur?Experiments show that:•No reaction occursif the alkane and halogen are kept in the dark and at low temperature•UV light or heat is requiredto start the reaction•Once the reaction begins, thelight or heat source can be removed, and the reaction willcontinue on its ownThis behavior is explained by thereaction mechanism.Why UV Light Is NeededIn methane:•Carbon–hydrogen (C–H) bonds arelow-polarity covalent bonds•The chlorine molecule (Cl₂) also has anonpolar covalent bondUV light has enough energy to:•Break the chlorine–chlorine bond(≈ 58 kcal/mol)Preview Mode
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