Haloalkanes and Haloarenes

  • Preparation of Haloalkanes
    • From alcohols
    • Examples:
      • Conversion of ethanol to ethyl bromide
      • Conversion of methanol to methyl iodide
    • Mechanism of reaction
      • Example reaction: Conversion of ethanol to ethyl bromide
        • Step 1: Protonation of alcohol
        • Step 2: Attack by halide ion
        • Step 3: Elimination of water
    • Factors affecting the reaction
      • Nature of alcohol
      • Nature of halide ion
      • Temperature and pressure
  • From alkyl halides
    • Examples:
      • Conversion of ethyl bromide to ethyl fluoride
      • Conversion of methyl bromide to ethyl chloride
    • Mechanism of reaction
      • Example reaction: Conversion of ethyl bromide to ethyl fluoride
        • Step 1: Nucleophilic substitution
        • Step 2: Protonation of fluoride ion
        • Step 3: Elimination of bromide ion
    • Factors affecting the reaction
      • Nature of alkyl halide
      • Nature of halogen ion
      • Temperature and pressure

Slide 11

  • From alcohols
    • Example: Conversion of ethanol to ethyl bromide
    • Equation:
      1. CH3CH2OH + HBr → CH3CH2Br + H2O
    • Mechanism:
      1. Protonation of alcohol
      2. Attack by halide ion
      3. Elimination of water
    • Factors affecting the reaction:
      • Nature of alcohol (primary, secondary, tertiary)
      • Nature of halide ion (fluoride, chloride, bromide, iodide)
      • Temperature and pressure

Slide 12

  • Mechanism of the conversion of ethanol to ethyl bromide
    • Step 1: Protonation of alcohol
      • Equation: CH3CH2OH + H+ → CH3CH2OH2+
    • Step 2: Attack by halide ion
      • Equation: CH3CH2OH2+ + Br- → CH3CH2Br + H2O
    • Step 3: Elimination of water (dehydration)
      • Equation: CH3CH2OH + HBr → CH3CH2Br + H2O

Slide 13

  • From alcohols
    • Example: Conversion of methanol to methyl iodide
    • Equation:
      1. CH3OH + HI → CH3I + H2O
    • Mechanism of the reaction
      1. Protonation of alcohol
      2. Attack by halide ion
      3. Elimination of water
    • Factors affecting the reaction
      • Nature of alcohol
      • Nature of halide ion
      • Temperature and pressure

Slide 14

  • Mechanism of the conversion of methanol to methyl iodide
    • Step 1: Protonation of alcohol
      • Equation: CH3OH + H+ → CH3OH2+
    • Step 2: Attack by halide ion
      • Equation: CH3OH2+ + I- → CH3I + H2O
    • Step 3: Elimination of water (dehydration)
      • Equation: CH3OH + HI → CH3I + H2O

Slide 15

  • From alkyl halides
    • Example: Conversion of ethyl bromide to ethyl fluoride
    • Equation:
      1. CH3CH2Br + 2KF → CH3CH2F + KBr
    • Mechanism of the reaction
      1. Nucleophilic substitution
      2. Protonation of fluoride ion
      3. Elimination of bromide ion
    • Factors affecting the reaction
      • Nature of alkyl halide
      • Nature of halogen ion
      • Temperature and pressure

Slide 16

  • Mechanism of the conversion of ethyl bromide to ethyl fluoride
    • Step 1: Nucleophilic substitution
      • Equation: CH3CH2Br + F- → CH3CH2F + Br-
    • Step 2: Protonation of fluoride ion
      • Equation: CH3CH2F + H+ → CH3CH2FH+
    • Step 3: Elimination of bromide ion
      • Equation: CH3CH2F + Br- → CH3CH2FH+ + Br-

Slide 17

  • From alkyl halides
    • Example: Conversion of methyl bromide to ethyl chloride
    • Equation:
      1. CH3Br + C2H5Cl → C2H5Br + CH3Cl
    • Mechanism of the reaction
      1. Nucleophilic substitution
      2. Protonation of chloride ion
      3. Elimination of bromide ion
    • Factors affecting the reaction
      • Nature of alkyl halide
      • Nature of halogen ion
      • Temperature and pressure

Slide 18

  • Mechanism of the conversion of methyl bromide to ethyl chloride
    • Step 1: Nucleophilic substitution
      • Equation: CH3Br + Cl- → CH3Cl + Br-
    • Step 2: Protonation of chloride ion
      • Equation: CH3Cl + H+ → CH3ClH+
    • Step 3: Elimination of bromide ion
      • Equation: CH3Cl + Br- → CH3ClH+ + Br-

Slide 19

  • Factors affecting the preparation of haloalkanes from alcohols and alkyl halides
    • Nature of alcohol or alkyl halide
      • Primary, secondary, tertiary
    • Nature of halogen ion
      • Fluoride, chloride, bromide, iodide
    • Temperature and pressure
      • Higher temperatures favor elimination reactions
      • Higher pressures favor substitution reactions

Slide 20

  • Summary
    • Haloalkanes can be prepared from alcohols and alkyl halides
    • Preparation from alcohols involves three main steps: protonation, attack by halide ion, and elimination of water
    • Preparation from alkyl halides involves nucleophilic substitution, protonation of halogen ion, and elimination of halide ion
    • The reaction conditions and the nature of the reactants determine the outcome of the reaction

Slide 21

  • Preparation of Haloalkanes
    • From alcohols
      • Examples:
        • Conversion of ethanol to ethyl bromide
        • Conversion of methanol to methyl iodide
      • Mechanism of reaction
        • Example reaction: Conversion of ethanol to ethyl bromide
          • Step 1: Protonation of alcohol
          • Step 2: Attack by halide ion
          • Step 3: Elimination of water
      • Factors affecting the reaction
        • Nature of alcohol
        • Nature of halide ion
        • Temperature and pressure

Slide 22

  • Preparation of Haloalkanes
    • From alkyl halides
      • Examples:
        • Conversion of ethyl bromide to ethyl fluoride
        • Conversion of methyl bromide to ethyl chloride
      • Mechanism of reaction
        • Example reaction: Conversion of ethyl bromide to ethyl fluoride
          • Step 1: Nucleophilic substitution
          • Step 2: Protonation of fluoride ion
          • Step 3: Elimination of bromide ion
      • Factors affecting the reaction
        • Nature of alkyl halide
        • Nature of halogen ion
        • Temperature and pressure

Slide 23

  • Conversion of ethanol to ethyl bromide
    • Example:
      1. CH3CH2OH + HBr → CH3CH2Br + H2O
    • Mechanism of the reaction:
      1. Protonation of alcohol: CH3CH2OH + H+ → CH3CH2OH2+
      2. Attack by halide ion: CH3CH2OH2+ + Br- → CH3CH2Br + H2O
      3. Elimination of water: CH3CH2OH + HBr → CH3CH2Br + H2O
    • Factors affecting the reaction:
      • Nature of alcohol (primary, secondary, tertiary)
      • Nature of halide ion (fluoride, chloride, bromide, iodide)
      • Temperature and pressure

Slide 24

  • Conversion of methanol to methyl iodide
    • Example:
      1. CH3OH + HI → CH3I + H2O
    • Mechanism of the reaction:
      1. Protonation of alcohol: CH3OH + H+ → CH3OH2+
      2. Attack by halide ion: CH3OH2+ + I- → CH3I + H2O
      3. Elimination of water: CH3OH + HI → CH3I + H2O
    • Factors affecting the reaction:
      • Nature of alcohol (primary, secondary, tertiary)
      • Nature of halide ion (fluoride, chloride, bromide, iodide)
      • Temperature and pressure

Slide 25

  • Conversion of ethyl bromide to ethyl fluoride
    • Example:
      1. CH3CH2Br + 2KF → CH3CH2F + KBr
    • Mechanism of the reaction:
      1. Nucleophilic substitution: CH3CH2Br + F- → CH3CH2F + Br-
      2. Protonation of fluoride ion: CH3CH2F + H+ → CH3CH2FH+
      3. Elimination of bromide ion: CH3CH2F + Br- → CH3CH2FH+ + Br-
    • Factors affecting the reaction:
      • Nature of alkyl halide (primary, secondary, tertiary)
      • Nature of halogen ion (fluoride, chloride, bromide, iodide)
      • Temperature and pressure

Slide 26

  • Conversion of methyl bromide to ethyl chloride
    • Example:
      1. CH3Br + C2H5Cl → C2H5Br + CH3Cl
    • Mechanism of the reaction:
      1. Nucleophilic substitution: CH3Br + Cl- → CH3Cl + Br-
      2. Protonation of chloride ion: CH3Cl + H+ → CH3ClH+
      3. Elimination of bromide ion: CH3Cl + Br- → CH3ClH+ + Br-
    • Factors affecting the reaction:
      • Nature of alkyl halide (primary, secondary, tertiary)
      • Nature of halogen ion (fluoride, chloride, bromide, iodide)
      • Temperature and pressure

Slide 27

  • Factors affecting the reaction
    • Nature of alcohol or alkyl halide
      • Primary, secondary, tertiary
    • Nature of halogen ion
      • Fluoride, chloride, bromide, iodide
    • Temperature and pressure
      • Higher temperatures favor elimination reactions
      • Higher pressures favor substitution reactions

Slide 28

  • Summary
    • Haloalkanes can be prepared from alcohols and alkyl halides
    • Preparation from alcohols involves protonation, attack by halide ion, and elimination of water
    • Preparation from alkyl halides involves nucleophilic substitution, protonation of halogen ion, and elimination of halide ion
    • The nature of reactants and reaction conditions determine the outcome of the reaction

Slide 29

  • Concept check:
    1. How can haloalkanes be prepared from alcohols and alkyl halides?
    2. What are the steps involved in the conversion of ethanol to ethyl bromide? Provide the mechanisms.
    3. Explain the factors that affect the preparation of haloalkanes from alcohols and alkyl halides.

Slide 30

  • Review
    • In this lecture, we learned about the preparation of haloalkanes from alcohols and alkyl halides
    • We discussed the mechanism of reactions and the factors that affect these reactions
    • We also looked at specific examples, such as the conversion of ethanol to ethyl bromide and the conversion of methyl bromide to ethyl chloride
    • Understanding these concepts will allow you to apply them in various chemical reactions and reactions involving haloalkanes-