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!
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