Radical Reactions

⚗️ Radical Reactions

Part 1 of 7 — Introduction to Radicals

1. Radicals

species with unpaired electrons

2. Homolytic cleavage

bond breaks evenly → two radicals

3. Radical reactions have three stages

initiation, propagation, termination

4. Radicals are highly reactive and short-lived

Radicals are highly reactive and short-lived

Concept Check 🎯

Key Concepts Summary

• Radicals: species with unpaired electrons
• Homolytic cleavage: bond breaks evenly → two radicals
• Radical reactions have three stages: initiation, propagation, termination
• Radicals are highly reactive and short-lived

Concept Check 🎯

Fill in the Blanks 🔍

Radical Halogenation

Part 2 of 7 — Radical Halogenation

1. Initiation

light or heat breaks X₂ → 2X•

2. Propagation step 1

X• + R-H → R• + HX

3. Propagation step 2

R• + X₂ → R-X + X•

4. Termination

any two radicals combine

Concept Check 🎯

Key Concepts Summary

• Initiation: light or heat breaks X₂ → 2X•
• Propagation step 1: X• + R-H → R• + HX
• Propagation step 2: R• + X₂ → R-X + X•
• Termination: any two radicals combine

Concept Check 🎯

Fill in the Blanks 🔍

Selectivity in Halogenation

Part 3 of 7 — Selectivity in Halogenation

1. Chlorination

low selectivity (3°:2°:1° ≈ 5:4:1)

2. Bromination

high selectivity (3°:2°:1° ≈ 1600:82:1)

3. Bromine is more selective because the H-abstraction step is endothermic

Bromine is more selective because the H-abstraction step is endothermic

4. NBS

N-bromosuccinimide for allylic/benzylic bromination

Concept Check 🎯

Key Concepts Summary

• Chlorination: low selectivity (3°:2°:1° ≈ 5:4:1)
• Bromination: high selectivity (3°:2°:1° ≈ 1600:82:1)
• Bromine is more selective because the H-abstraction step is endothermic
• NBS: N-bromosuccinimide for allylic/benzylic bromination

Concept Check 🎯

Fill in the Blanks 🔍

Radical Addition to Alkenes

Part 4 of 7 — Radical Addition to Alkenes

1. Anti-Markovnikov addition of HBr with peroxides

Anti-Markovnikov addition of HBr with peroxides

2. Radical adds to less substituted carbon (more stable radical at more substituted)

Radical adds to less substituted carbon (more stable radical at more substituted)

3. Only works with HBr (not HCl or HI)

Only works with HBr (not HCl or HI)

4. Polymerization

radical chain growth of alkenes

Concept Check 🎯

Key Concepts Summary

• Anti-Markovnikov addition of HBr with peroxides
• Radical adds to less substituted carbon (more stable radical at more substituted)
• Only works with HBr (not HCl or HI)
• Polymerization: radical chain growth of alkenes

Concept Check 🎯

Fill in the Blanks 🔍

Radical Stability

Part 5 of 7 — Radical Stability

1. Radical stability

3° > 2° > 1° > methyl (same as carbocations)

2. Allylic and benzylic radicals

stabilized by resonance

3. Bond dissociation energy (BDE)

energy to break bond homolytically

4. Lower BDE = easier radical formation

Lower BDE = easier radical formation

Concept Check 🎯

Key Concepts Summary

• Radical stability: 3° > 2° > 1° > methyl (same as carbocations)
• Allylic and benzylic radicals: stabilized by resonance
• Bond dissociation energy (BDE): energy to break bond homolytically
• Lower BDE = easier radical formation

Concept Check 🎯

Fill in the Blanks 🔍

Problem-Solving Workshop

Part 6 of 7 — Problem-Solving Workshop

1. Drawing radical mechanisms

Drawing radical mechanisms

2. Predicting halogenation products and selectivity

Predicting halogenation products and selectivity

3. Comparing radical vs ionic pathways

Comparing radical vs ionic pathways

4. Analyzing BDE data

Analyzing BDE data

Concept Check 🎯

Key Concepts Summary

• Drawing radical mechanisms
• Predicting halogenation products and selectivity
• Comparing radical vs ionic pathways
• Analyzing BDE data

Concept Check 🎯

Fill in the Blanks 🔍

Synthesis & Review

Part 7 of 7 — Synthesis & Review

1. Radical reactions follow distinct mechanistic patterns

Radical reactions follow distinct mechanistic patterns

2. Selectivity depends on halogen choice

Selectivity depends on halogen choice

3. Radical stability parallels carbocation stability

Radical stability parallels carbocation stability

4. Review

radical halogenation and addition

Concept Check 🎯

Key Concepts Summary

• Radical reactions follow distinct mechanistic patterns
• Selectivity depends on halogen choice
• Radical stability parallels carbocation stability
• Review: radical halogenation and addition

Concept Check 🎯

Fill in the Blanks 🔍