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15. Halogen compounds

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  1. 15.1 Halogenoalkanes

    1. 15.1.1Preparation of halogenoalkanes

      • Recall preparation of halogenoalkanes - (a) the free-radical substitution of alkanes by Cl 2 or Br2 with ultraviolet light, as exemplified by the reactions of ethane - (b) electrophilic addition of an alkene with a halogen, X 2, or hydrogen halide, HX(g), at room temp. - (c) substitution of an alcohol, e.g. by reaction with HX(g); or with KCl and conc. H2SO4 or conc. H3PO4; or with PCl 3 and heat; or with PCl5; or with SOCl 2

    2. 15.1.2Classify halogenoalkanes into primary,

      • Classify halogenoalkanes into primary, secondary and tertiary

    3. 15.1.3Nucleophilic substitution

      • Describe the following nucleophilic substitution reactions: - (a) the reaction with NaOH(aq) and heat to produce an alcohol - (b) the reaction with KCN in ethanol and heat to produce a nitrile - (c) the reaction with NH3 in ethanol heated under pressure to produce an amine - (d) the reaction with aq. silver nitrate in ethanol as a method of identifying the halogen present as exemplified by bromoethane

    4. 15.1.4Elimination reaction with NaOH in ethanol

      • Describe the elimination reaction with NaOH in ethanol and heat to produce an alkene as exemplified by bromoethane

    5. 15.1.5SN1/SN2 substitution mechanisms

      • Describe the SN1 and SN2 mechanisms of nucleophilic substitution in halogenoalkanes including the inductive effects of alkyl groups

    6. 15.1.6SN2/SN1 trends in halogenoalkanes

      • Recall that primary halogenoalkanes tend to react via the SN2 mechanism; tertiary halogenoalkanes via the SN1 mechanism; and secondary halogenoalkanes by a mixture of the two, depending on structure

    7. 15.1.7Rate of hydrolysis of halogenoalkanes

      • Describe/explain: the different reactivities of halogenoalkanes (with particular reference to the relative strengths of the C–X bonds as exemplified by the reactions of halogenoalkanes with aq. silver nitrates)