Substitution Reactions and Distillation

Lab Goals

• Two week lab– Week 2: We want to ask a question about

elimination reactions, but we don’t have one of the reagents: 2-chloro-2-methylbutane

– Week 1 Goal: Make at least 3.0 mL of 2-chloro-2-methylbutane

Cl

baseProduct Distribution?

Substitution Reaction

• Mechanistic Possibilities?• Propose a mechanism for reaction• How does the mechanism affect the practical

aspects of the reaction?– Choice of solvent– Heat or cool?

ClOH

conc. HCl

Experimental Flowchart

• Conduct the reaction• Crude purification: Extraction– Purpose of base and brine extraction

• Mainly purified liquid: How do we further purify and characterize?– Melting point?– Recrystallize?– TLC?

Distillation

• Purification• Characterization

What’s wrong here?

Separation and Boiling Point35o 126o

Separation of Pentane and Octane• Starting with 75% octane/

25% pentane– L1: 75/25 mixture boils at

77oC– V1: at same temperature,

composition is 15%/85%– L2: liquid condenses on glass

as 15/85 mixture– V2: second vaporization is

again enriched: 99% pure pentane

Fractional Distillation

• Separation of pentane and hexane• Theoretical plates• Limitation: azeotropes (non-ideal solutions)

Reaction Flowchart

• Conduct the reaction• Crude purification: Extraction• Final Purification and Characterization:

Distillation– Proper set up– Do not allow to go to dryness

• Save product for next week!