CHEM 2211L Comprehensive Lab Final Study Guide Winter 2026

🧪StudyCHEM 2211L Comprehensive Lab Final
Guide
📘 Overview
Your lab final tests understanding, not memorization. Focus on:

 Why each reagent or technique was used.
 How the mechanisms and separations worked.
 Interpreting data (TLC, melting point, GC, NMR, IR).
 Predicting outcomes when conditions or reactants change.




🧊 Experiment 1: Recrystallization
Purpose: Purify an impure solid and identify it via melting point comparison.
Techniques: Recrystallization, gravity/suction filtration, melting point determination.
Concepts to Know:

 Solubility behavior of solids (hot vs. cold solvent).
 How impurities are removed.
 Purpose of minimal solvent use.
 Role of scratching to induce crystallization.
 Interpreting melting point (pure → sharp, impure → broad/depressed).

Sample Exam Questions:

1. (MC) Why is the minimal amount of hot solvent used in recrystallization?
A. To dissolve impurities

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B. To increase solubility of impurities
C. To maximize recovery of the purified compound
D. To avoid bumping
2. (Short Answer) Explain how a mixed melting point test can confirm the identity of an
unknown compound.




🌡️ Experiment 2: Simple & Fractional Distillation
Purpose: Separate and identify two miscible liquids based on boiling point.
Techniques: Simple vs. fractional distillation, boiling point determination.
Concepts to Know:

,  Simple distillation is best for large BP differences (>100 °C).
 Fractional distillation uses a column for repeated vaporization-condensation cycles
(better separation).
 Role of boiling chips and why never boil to dryness.
 Azeotrope concept (ethanol-water).

Sample Exam Questions:

1. (MC) Which setup provides the most efficient separation of two liquids differing by 15

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°C in boiling point?
Fractional distillation
2. (Short Answer) Why must you never distill to dryness?




🌰 Experiment 3: Solid-Liquid Extraction (Trimyristin
from Nutmeg)
Purpose: Extract a triglyceride using solvent solubility.
Techniques: Reflux, gravity filtration, simple distillation, vacuum filtration, melting point
determination.
Concepts to Know:

 Ethyl acetate dissolves trimyristin (nonpolar) from nutmeg.
 Acetone wash removes impurities.
 Solubility-driven separation principle.
 Difference between solid-liquid and liquid-liquid extraction.

Sample Exam Questions:


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1. (MC) What physical property enables trimyristin to be separated from nutmeg?
Solubility in ethyl acetate
2. (Short Answer) Why is acetone used to wash the crystals?




💊 Experiment 4: Thin Layer Chromatography (TLC)
Purpose: Identify analgesic components in mixtures.
Techniques: TLC, visualization with UV light, Rf value calculation.
Concepts to Know:

 Rf = (distance traveled by compound) / (distance traveled by solvent front).
 Polar compounds travel less on polar silica plates.
 Solvent polarity affects migration.

,  Uses: compound ID, reaction progress, purity check.

Sample Exam Questions:


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1. (MC) Increasing solvent polarity in TLC will:
Increase Rf values for most compounds
2. (Short Answer) How can TLC confirm completion of a reaction?




⚗️ Experiment 6: Acid/Base Extraction
Purpose: Separate acidic, basic, and neutral compounds using solubility changes.
Techniques: Liquid-liquid extraction, separatory funnel use, drying agents, IR and ¹H NMR
analysis.
Concepts to Know:

 Acids → deprotonated by base → move to aqueous layer.
 Bases → protonated by acid → move to aqueous layer.
 Neutral compounds remain in organic layer.
 Drying agents (Na₂SO₄) remove water.
 IR identifies functional groups; ¹H NMR identifies structure and purity.

Sample Exam Questions:


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1. (MC) During extraction, benzoic acid is transferred to the aqueous layer by:
Deprotonation with NaOH
2. (Short Answer) Explain how IR and NMR can confirm compound identity after
extraction.




🫒 Experiment 7: Transfer Hydrogenation of Olive Oil
Purpose: Convert unsaturated fat (triolein) to saturated fat (tristearin) using cyclohexene as H
donor.
Techniques: Reflux, celite filtration, melting point determination.
Concepts to Know:

 Transfer hydrogenation avoids explosive H₂ gas.
 Pd/C acts as catalyst; cyclohexene donates hydrogen.
 Melting point increases as saturation increases.

Sample Exam Questions:

, ✅
1. (MC) The function of cyclohexene in this experiment is to:
Act as a hydrogen donor (reducing agent)
2. (Short Answer) Why does tristearin have a higher melting point than triolein?




💎 Experiment 8: Preparation of Diphenylacetylene
Purpose: Synthesize an alkyne from an alkene via halogenation + double dehydrohalogenation.
Techniques: Reflux, recrystallization, melting point determination.
Concepts to Know:

 PHPB = safer bromine source.
 Step 1: Electrophilic addition of Br₂ to trans-stilbene.
 Step 2: Double elimination (E2) with KOH → diphenylacetylene.
 Melting point confirms purity and identity.

Sample Exam Questions:


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1. (MC) The reagent PHPB serves as a:
Source of bromine for electrophilic addition
2. (Mechanism Completion)**: Show how KOH converts stilbene dibromide to
diphenylacetylene.




💨 Experiment 9: Gas Chromatography (SN1 Reaction with
tert-Butanol)
Purpose: Determine relative nucleophilicity of bromide vs chloride via SN1 substitution.
Techniques: Gas chromatography, microscale liquid-liquid extraction.
Concepts to Know:

 Reaction forms tert-butyl bromide and tert-butyl chloride.
 SN1 mechanism (carbocation intermediate).
 GC separates products by volatility; peak area ∝ product amount.
 Bromide = stronger nucleophile, chloride = weaker.

Sample Exam Questions:


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1. (MC) Why can’t tert-butanol undergo SN2 substitution?
Steric hindrance at the tertiary carbon
2. (Data Interpretation) In a GC trace, if tert-butyl bromide has a larger peak than tert-butyl
chloride, what does this indicate about nucleophilic strength?