Synthesis and Reactivity of tert-Butyl Chloride

Experiment Overview

  • Synthesis of tert-Butyl Chloride via SN1 Reaction

  • Reactants: tert-Butyl alcohol, HCl (conc.)

  • Product: 2-chloro-2-methylpropane (tert-butyl chloride)

Objectives

  • Prepare tert-butyl chloride from tert-butyl alcohol

  • Examine reactivity of alkyl halides using qualitative tests (AgNO3, NaI)

Alkyl Halides

  • Compounds with a halogen atom replacing a hydrogen atom

  • Can be transformed into other functional groups

Nucleophilic Substitution Reactions

  • Two types: SN1 (first-order, unimolecular), SN2 (second-order)

  • Today's focus: SN1 reaction

  • Key points:

    • Slow rate-determining step with alkyl halide

    • Carbocation stability determines reaction pathway (3º > 2º > 1º)

Factors Favoring SN1 Reactions

  • Best with 3° alkyl halides (more stable carbocations)

  • Polar solvents (stabilize carbocations)

  • Weak nucleophiles

  • Good leaving groups (I- > Br- > Cl- > OH-)

Reaction Mechanism

  • Produces a 3° carbocation as an intermediate

  • Followed by nucleophile attack and leaving group departure

Experimental Procedures

  • Part A: Synthesis of tert-butyl chloride

    • Utilize separatory funnel for extraction

    • Use simple distillation for purification

  • Part B: Qualitative Tests

    • Silver Nitrate Test: positive for 3° alkyl halides

    • Sodium Iodide Test: positive for 1° alkyl halides

Distillation Setup

  • Essential for separating compounds based on boiling points

  • More efficient with boiling point difference > 10 °C

Qualitative Tests Reactivity Order

  1. NaI Test (SN2) - 1° > 2° > 3° alkyl halides

  2. AgNO3 Test (SN1) - 3° > 2° > 1° alkyl halides

Summary of Experimental Steps

  1. Combine tert-butyl alcohol and concentrated HCl in separatory funnel

  2. Extract organic layer and neutralize residual acid with NaHCO3

  3. Dry product with CaCl2, then perform simple distillation

  4. Test reactivity of product with NaI and AgNO3