Orgo 2 Lab Final Exam

Objective: Synthesize a bicyclic compound from butadiene and maleic anhydride under reflux conditions.
- Butadiene is generated in-situ by cracking sulfolene, reacting with maleic anhydride.
- Reaction type: [4+2] cycloaddition.
- Mechanism involves interaction between HOMO of diene and LUMO of dienophile.
- Diels-Alder reaction is concerted; stereochemistry is retained.
- Sulfolene decomposes to provide butadiene, which is a gas and cannot directly enter the mixture.
- Utilizing a deuterated solvent enhances NMR signal resolution.
- Reducing solvent concentration avoids drowning out analyte signals.

Definition: Purification technique that separates solids from impurities based on solubility differences.
- The solid compound is dissolved in hot solvent (solvent must be highly soluble for the compound at high temperatures, but insoluble at low temperatures).
- Impurities should remain insoluble in the hot solvent.
- Process:
  - Filter hot solution to remove impurities.
  - Cool to room temperature to allow crystals to form; placing in an ice bath promotes crystallization.
  - Collect crystals via vacuum filtration, wash with cold solvent, and dry under vacuum.
- Key property: Solubility differentiation at various temperatures.

Lab Jack: Used to lower reaction temperature during reflux, avoiding contact with hot surfaces.

Slow Heating: Ensures thorough dissolution of all reactants. Rapid heating may waste sulfolene's effectiveness.
Reflux: Retains high temperature, accelerating reaction and minimizing loss through evaporation.

Purpose: Washes away nonpolar impurities (xylenes) post-reaction. Low boiling point of petroleum ethers aids in crystallization.

Objective: Synthesize fluorescein from resorcinol and phthalic anhydride in presence of sulfuric acid.
- Fluorescence observed under UV light.
- Chemiluminescence: Luminol reacts with hydrogen peroxide and iron catalyst to emit light.
- Electron Behavior: Light/heat excite electrons to higher energy levels; their return emits visible light.
- Fluorescence vs. Phosphorescence:
  - Singlet state relaxation: Fluorescence.
  - Triplet state relaxation: Phosphorescence.

Conjugation Impact: Increased conjugation reduces HOMO-LUMO gap; less energy required for electron excitation.
- Wavelength-Energy Relation:
  - Shorter wavelength = higher energy; longer wavelength = lower energy.
Visible Spectrum Interpretation:
- Black: all light absorbed.
- White: all visible light emitted.
- Green emission corresponds to absorption of red light. Dark spots on TLC indicate absorbed short wavelengths.

Objective: Synthesize 4-bromoacetanilide from aniline.
- Step 1: Acetylation of an amine protects it from undesired reactions in electrophilic aromatic substitution (EAS).
- Step 2: Perform para-bromination.

Protecting the amine as an amide helps it remain an ortho/para director, avoiding protonation and deactivation.

Objective: Use EAS to synthesize azo dye from nitroaniline and salicylic acid.
- Process:
  - Nitroaniline forms diazonium salts acting as electrophiles in EAS.

Scratching flask introduces nucleation sites for crystal formation.
Using antisolvent increases saturation, triggering nucleation and crystal growth.

Salicylic acid is the nucleophile; its hydroxyl group facilitates the donation of electron density.
- 4-Nitroaniline stabilizes the diazonium salt due to the electron-withdrawing effect.

Objective: Perform NAS with aryl fluoride and substituted phenol.
- K2CO3 deprotonates OH, enhancing nucleophilicity.
- DMSO solvent facilitates both organic and aqueous compounds.
- Brine Extraction: Pushes organic compounds into organic layers, helping with emulsion separation.

Na2SO4 function: Removes water, concentrating organic compounds while ensuring proper drying.

DMSO as an amphiphilic solvent enhances interactions between reactants. Prevents unwanted reactions during nucleophile attacks.

Objective: Synthesize substituted benzophenones under reflux via Friedel-Crafts acylation.
- AlCl3 activates alkyl halide, forming reactive acylium ion.
- Electron donating groups enhance nucleophilicity.
- Electron withdrawing groups reduce electron density on the ring.

Objective: Synthesize esters by combining alcohols and carboxylic acids with H2SO4 as a catalyst.

Limiting Reagent: Difficult to purify, ideally chosen on cost and toxicity.
Excess Reagent: Should be easy to purify; use of acid promotes ester formation.

Objective: Combine aldehydes and ketones in base to form cross aldol product.
- Alpha hydrogens in carbonyls are more acidic than in alkanes or alkenes due to resonance stabilization of the enolate anion.

Significant yield facilitated by the presence of a reactant without alpha hydrogens to reduce self-condensation.

Objective: Synthesize substituted benzophenones.
- Acylation generates acylium ions that react with benzene, disrupting aromaticity but restoring it via elimination.