Orgo Lab Quiz + Practicum

Some basic chem about Orgo 2 Labs 1-5 and basic experimental set ups

Reaction: Secondary alcohol → ketone

Oxidation of Cyclohexanol

Reagent: Sodium hypochlorite (NaOCl, bleach)

Oxidation of Cyclohexanol

Why is the Oxidation of Cyclohexanol green chemistry?

Green chemistry (replaces toxic chromium reagents)

Product: Cyclohexanone

Oxidation of Cyclohexanol

→ If they ask mechanism: involves HOCl formation + oxidation via hypochlorite

Important concept:

• Oxidation = increase in C–O bonds / decrease in C–H

• Byproducts = water + salt (much safer)

Oxidation of Cyclohexanol

Reaction type: Electrophilic Aromatic Substitution (EAS)

Bromination of Acetanilide (EAS)

Goal: Add Br to benzene ring

Bromination of Acetanilide (EAS)

Reagents: KBr + CAN (ceric ammonium nitrate) → makes brominating species in situ

Bromination of Acetanilide (EAS)

Why is Bromination of Acetanilide (EAS) green chemistry?

Avoids using Br₂ directly (toxic, dangerous)

Mechanism of Bromination of Acetanilide

Key mechanism steps:

1. Generate electrophile (Br⁺ or equivalent)

2. Benzene ring attacks → sigma complex

3. Deprotonation → restores aromaticity

Is Bromination of Acetanilide ortho or para directing?

Acetanilide is ortho/para directing, but:

• Para product dominates (less steric hindrance)

Fluorescence in Fluorescence vs Chemiluminescence lab

1. Fluorescence

• Light absorbed → excited state → emits light

• Equation:

  • E=hcλE = \frac{hc}{\lambda}E=λhc​

• Fluorescein

  • Emits green light (~525 nm)

  • pH-dependent structure → changes intensity/color

Chemiluminescence in Chemi and fluorescence Lab

2. Chemiluminescence (Luminol)

• Light produced from a chemical reaction, not light absorption

• Example:

  • Luminol + oxidizer → excited product → emits light

• Key requirements:

  1. Enough energy from reaction

  2. Pathway to excited state

  3. Light emission or energy transfer

👉 Classic example: forensic blood detection

this lab involved:

• NaBH₄ (sodium borohydride)

• Possibly comparing with LiAlH₄

Reduction of Camphor

Reductions in Reduction of Camphor

Core Concept:

Reduction of carbonyls → alcohols

• Aldehyde → 1° alcohol

• Ketone → 2° alcohol

What does NABH₄ do In reduction of camphor?

What NaBH₄ does:

• Donates hydride (H⁻) → attacks C=O

• Then protonation → alcohol

Reagent Strength Differences in reduction of camphor

Reagent	Strength	What it reduces
NaBH₄	mild	aldehydes + ketones
LiAlH₄	strong	esters, carboxylic acids, amides (everything basically)

Products in Reduction of Camphor

Borneol and Isoborneal (major product)

Reaction Mechanism of Synthesis of Salicylic Acid

Ester + Base → Carboxylate salt(soap) + Alcohol

Products of Synthesis of Salicylic Acid

• Product is carboxylate salt, NOT acid

• You need acid workup (H₃O⁺) to get the acid

Why NaOH vs KOH in Synthesis of Salicylic Acid

• Both work the same (both strong bases)

• Difference is just the cation (Na⁺ vs K⁺)

Q: Difference: extraction vs washing

• Extraction = separates compounds

• Washing = removes impurities

Organic layer vs aqueous layer—how to tell?

Depends on solvent density (chloroform = bottom, ether = top)

Lab 1 Spam Questions

LAB 1: Oxidation (Cyclohexanol)

• Q: What functional group change occurs?
  A: Alcohol → ketone

• Q: What type of alcohol can be oxidized to ketone?
  A: Secondary alcohol

• Q: Why is NaOCl “green”?
  A: Less toxic, produces safer byproducts (water + salt)

• Q: Oxidation definition (orgo)
  A: Increase C–O or decrease C–H bonds

Lab 2 spam Questions

LAB 2: EAS Bromination

• Q: What is the electrophile in bromination?
  A: Br⁺ (or equivalent electrophilic bromine)

• Q: What is a sigma complex?
  A: Non-aromatic intermediate formed after attack

• Q: Why is acetanilide ortho/para directing?
  A: Electron-donating amide group

• Q: Why is para product major?
  A: Less steric hindrance

• Q: Why generate bromine in situ?
  A: Safer, avoids toxic Br₂ buildup`

Lab 3 Spam Questions

LAB 3: Fluorescence & Luminol

• Q: Fluorescence vs chemiluminescence
  A:

  • Fluorescence = light from absorbed energy

  • Chemiluminescence = light from chemical reaction

• Q: What does wavelength relate to?
  A: Energy (shorter λ = higher energy)

• Q: Why does fluorescein depend on pH?
  A: Structure changes with protonation → changes emission

• Q: What must happen for chemiluminescence?
  A: Reaction produces excited-state molecule

Lab 4 Spam Questions

LAB 4: Reduction (NaBH₄)

• Q: What does NaBH₄ provide?
  A: Hydride (H⁻)

• Q: Aldehyde → ?
  A: 1° alcohol

• Q: Ketone → ?
  A: 2° alcohol

• Q: Why is NaBH₄ safer than LiAlH₄?
  A: Less reactive, works in protic solvents

• Q: What bond is broken in reduction?
  A: C=O π bond

---

Lab 5 Spam Questions

LAB 5: Saponification

• Q: What is saponification?
  A: Base hydrolysis of ester

• Q: Products of saponification
  A: Carboxylate salt + alcohol

• Q: Why is reaction irreversible?
  A: Carboxylate is stabilized (won’t reform ester)

• Q: What step gives carboxylic acid?
  A: Acid workup (H₃O⁺)

• Q: Real-world example
  A: Soap formation

Final Overall Spam Questions:

• Q: Why does EAS preserve aromaticity?
  A: Final step restores conjugated π system

• Q: Why is NaBH₄ selective?
  A: Only reacts with highly polarized C=O

• Q: Why do oxidation reactions often use acids?
  A: Activate oxidizing agent (like HOCl formation)

• Q: Why does chemiluminescence often involve oxidation?
  A: Releases enough energy to excite electrons

Demonstrate everything you need to know about liquid-liquid extraction!

• Vent separatory funnel (VERY tested)

• Mix gently to avoid emulsions

Q: What happens if you don’t vent?
A: Pressure buildup → stopper can pop off

Steps:

1. Add mixture to separatory funnel

2. Add second solvent

3. Shake + VENT

4. Let layers separate

5. Drain bottom layer

6. Repeat if needed

⚠ VERY TESTED:

• Why vent?
  → Release pressure (prevent explosion)

• How identify layers?
  → Density (chloroform = bottom)

• What if emulsion forms?
  → Wait or add salt

• Extraction vs washing:

  • Extraction = move compound

  • Washing = remove impurities

How to Wash An Organic Layer

2. Washing an Organic Layer

• Remove impurities (acid, base, salts)

• Common washes:

  • Water → removes polar stuff

  • NaHCO₃ → removes acids

  • HCl → removes bases

👉 Key idea:

• Washing ≠ extracting (professors test this a lot)

How to dry an organic layer

• Use drying agents (CaCl₂, MgSO₄)

• Know:

  • Add until free-flowing powder

  • Swirl + wait

Steps:

1. Add drying agent (MgSO₄ or CaCl₂)

2. Swirl → wait

3. Look for free-flowing powder

4. Remove drying agent by:

   • Gravity filtration OR

   • Decanting

⚠ Must-know:

• What does drying agent remove?
  → Water

• How do you know it's done?
  → No clumping

• BIG TRICK:
  Drying agent is a solid impurity → must be removed before evaporation

How to do gravity filtration

• Remove solid impurities

• Used when product is in solution

👉 NOT for collecting crystals

How to perform Vacuum (Büchner) Filtration

• What you should know how to do:

  • Set up: Büchner funnel + filter paper + vacuum flask

  • Turn on vacuum → wet filter paper → pour mixture

  • Wash crystals with cold solvent

  • Let air pull through to dry

  High-yield questions:

  • Why use vacuum filtration?
    → To collect solid quickly

  • Why use cold solvent?
    → Prevent dissolving your product

  • What happens if vacuum isn’t tight?
    → Poor suction → slow filtration

How to do Recrystallization

• Purify solid compounds

• Steps:

  1. Dissolve in hot solvent

  2. Cool slowly → crystals form

  3. Filter + dry

👉 Key concept:

• Solvent must dissolve compound hot, not cold

How to measure melting point

• Determines:

  • Purity (sharp vs broad range)

  • Identity

👉 Flashcard:

• Impure sample → lower + broader melting point

HNMR sample preparation

Steps:

1. Dissolve small amount of sample

2. Use deuterated solvent (e.g., CDCl₃)

3. Transfer to NMR tube (clean + clear)

4. Fill to proper height (~5 cm)

⚠ High-yield:

• Why deuterated solvent?
  → Doesn’t show up in ¹H NMR

• Why small amount?
  → Too concentrated = messy peaks

• What happens if dirty tube?
  → Contaminated spectrum

Reflux Set Up

✅ What’s happening:

• Heating reaction without losing solvent

✅ Setup:

• Round-bottom flask

• Condenser on top

• Water flowing (in bottom → out top)

• Heat source below

⚠ MUST KNOW:

• Why reflux?
  → Speeds reaction while preventing evaporation

• Why water flows bottom → top?
  → Keeps condenser full

• What happens without condenser?
  → Solvent evaporates → reaction fails

Each Technique Final Practice

For each technique, be ready to answer:

• What is the purpose?

• What could go wrong?

• Why is each step necessary?