Radical Reactions - Complete Interactive Lesson
Part 1: Introduction to Radicals
Radical Reactions
**Part 1 of 7 — Radical Mechanism Foundations**
This part focuses on tracking chain reactions under thermal or photochemical conditions. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **homolysis**: bond cleavage giving one electron to each fragment
- **radical chain**: self-propagating sequence of radical steps
- **initiation**: step that first generates radicals
- **propagation**: steps that consume and regenerate radicals
### Worked reaction example
A representative transformation uses **Br2, hν**.
1. Identify the governing mechanism: **radical halogenation**.
2. Predict the dominant product pattern: **alkyl bromide at most substituted site**.
3. Justify with a mechanistic note: Br· is selective.
Exam tip: state mechanism class before drawing product. It reduces avoidable regio- and stereochemistry errors.
Mechanism checkpoint (2 questions)
Deep-Dive: Reaction Pattern Table
Use this table as a rapid decision grid.
| Reagents | Conditions / Mechanistic Trigger | Product Pattern | Why it works |
|---|---|---|---|
| Br2, hν | radical halogenation | alkyl bromide at most substituted site | Br· is selective |
| Cl2, hν | radical chlorination | mixture of chlorinated products | less selective than bromination |
| NBS, hν | allylic bromination | allylic bromide | maintains alkene position overall |
| HBr, ROOR | radical addition to alkene | anti-Markovnikov bromoalkane | chain process with Br· |
### Fast interpretation protocol
1. Map reagent set to mechanism family.
2. Apply regio- or stereochemical rule attached to that family.
3. Check whether rearrangement, equilibration, or reversibility changes the major product call.
Input Practice — enter exact chemistry terms
1) Term for: bond cleavage giving one electron to each fragment
2) Term for: self-propagating sequence of radical steps
3) Product pattern expected under Br2, hν
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Initiation is usually short; propagation controls product distribution.
- Bromination is slower but more selective than chlorination.
- Peroxide effect is classically reliable for HBr, not broadly all HX.
### High-yield exam sequence
1. **Read reagents before substrate details** to classify mechanism class quickly.
2. **Mark the reactive site** (electrophilic carbon, acidic alpha-carbon, benzylic/allylic position, or aromatic position).
3. **Commit to one major-product logic path** before checking answer choices.
4. **Audit stereochemistry and regiochemistry last** so you do not lose points on orientation errors.
### Timing technique
If two options differ only by orientation or placement, spend 10 seconds restating the governing rule out loud (Markovnikov, anti addition, kinetic control, etc.) before selecting.
Applied synthesis/mechanism check (2 questions)
Part 2: Radical Halogenation
Radical Reactions
**Part 2 of 7 — Initiation, Propagation, Termination**
This part focuses on identifying where radicals are generated and consumed. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **radical chain**: self-propagating sequence of radical steps
- **initiation**: step that first generates radicals
- **propagation**: steps that consume and regenerate radicals
- **termination**: radical-radical combination removing chain carriers
### Worked reaction example
A representative transformation uses **Cl2, hν**.
1. Identify the governing mechanism: **radical chlorination**.
2. Predict the dominant product pattern: **mixture of chlorinated products**.
3. Justify with a mechanistic note: less selective than bromination.
Exam tip: state mechanism class before drawing product. It reduces avoidable regio- and stereochemistry errors.
Mechanism checkpoint (2 questions)
Deep-Dive: Reaction Pattern Table
Use this table as a rapid decision grid.
| Reagents | Conditions / Mechanistic Trigger | Product Pattern | Why it works |
|---|---|---|---|
| Cl2, hν | radical chlorination | mixture of chlorinated products | less selective than bromination |
| NBS, hν | allylic bromination | allylic bromide | maintains alkene position overall |
| HBr, ROOR | radical addition to alkene | anti-Markovnikov bromoalkane | chain process with Br· |
| AIBN initiator | radical generation | chain starts under heat | common azo initiator |
### Fast interpretation protocol
1. Map reagent set to mechanism family.
2. Apply regio- or stereochemical rule attached to that family.
3. Check whether rearrangement, equilibration, or reversibility changes the major product call.
Input Practice — enter exact chemistry terms
1) Term for: self-propagating sequence of radical steps
2) Term for: step that first generates radicals
3) Product pattern expected under Cl2, hν
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Bromination is slower but more selective than chlorination.
- Peroxide effect is classically reliable for HBr, not broadly all HX.
- Radical inhibitors can suppress chain length and conversion.
### High-yield exam sequence
1. **Read reagents before substrate details** to classify mechanism class quickly.
2. **Mark the reactive site** (electrophilic carbon, acidic alpha-carbon, benzylic/allylic position, or aromatic position).
3. **Commit to one major-product logic path** before checking answer choices.
4. **Audit stereochemistry and regiochemistry last** so you do not lose points on orientation errors.
### Timing technique
If two options differ only by orientation or placement, spend 10 seconds restating the governing rule out loud (Markovnikov, anti addition, kinetic control, etc.) before selecting.
Applied synthesis/mechanism check (2 questions)
Part 3: Selectivity in Halogenation
Radical Reactions
**Part 3 of 7 — Halogenation Selectivity**
This part focuses on predicting regioselectivity from radical stability. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **initiation**: step that first generates radicals
- **propagation**: steps that consume and regenerate radicals
- **termination**: radical-radical combination removing chain carriers
- **radical stability**: tertiary and resonance-stabilized radicals are favored
### Worked reaction example
A representative transformation uses **NBS, hν**.
1. Identify the governing mechanism: **allylic bromination**.
2. Predict the dominant product pattern: **allylic bromide**.
3. Justify with a mechanistic note: maintains alkene position overall.
Exam tip: state mechanism class before drawing product. It reduces avoidable regio- and stereochemistry errors.
Mechanism checkpoint (2 questions)
Deep-Dive: Reaction Pattern Table
Use this table as a rapid decision grid.
| Reagents | Conditions / Mechanistic Trigger | Product Pattern | Why it works |
|---|---|---|---|
| NBS, hν | allylic bromination | allylic bromide | maintains alkene position overall |
| HBr, ROOR | radical addition to alkene | anti-Markovnikov bromoalkane | chain process with Br· |
| AIBN initiator | radical generation | chain starts under heat | common azo initiator |
| thiol-ene conditions | radical addition | anti-Markovnikov thioether | useful click-like transformation |
### Fast interpretation protocol
1. Map reagent set to mechanism family.
2. Apply regio- or stereochemical rule attached to that family.
3. Check whether rearrangement, equilibration, or reversibility changes the major product call.
Input Practice — enter exact chemistry terms
1) Term for: step that first generates radicals
2) Term for: steps that consume and regenerate radicals
3) Product pattern expected under NBS, hν
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Peroxide effect is classically reliable for HBr, not broadly all HX.
- Radical inhibitors can suppress chain length and conversion.
- Initiation is usually short; propagation controls product distribution.
### High-yield exam sequence
1. **Read reagents before substrate details** to classify mechanism class quickly.
2. **Mark the reactive site** (electrophilic carbon, acidic alpha-carbon, benzylic/allylic position, or aromatic position).
3. **Commit to one major-product logic path** before checking answer choices.
4. **Audit stereochemistry and regiochemistry last** so you do not lose points on orientation errors.
### Timing technique
If two options differ only by orientation or placement, spend 10 seconds restating the governing rule out loud (Markovnikov, anti addition, kinetic control, etc.) before selecting.
Applied synthesis/mechanism check (2 questions)
Part 4: Radical Addition to Alkenes
Radical Reactions
**Part 4 of 7 — Allylic and Benzylic Radical Chemistry**
This part focuses on using resonance-stabilized radical intermediates. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **propagation**: steps that consume and regenerate radicals
- **termination**: radical-radical combination removing chain carriers
- **radical stability**: tertiary and resonance-stabilized radicals are favored
- **allylic radical**: radical adjacent to C=C with resonance support
### Worked reaction example
A representative transformation uses **HBr, ROOR**.
1. Identify the governing mechanism: **radical addition to alkene**.
2. Predict the dominant product pattern: **anti-Markovnikov bromoalkane**.
3. Justify with a mechanistic note: chain process with Br·.
Exam tip: state mechanism class before drawing product. It reduces avoidable regio- and stereochemistry errors.
Mechanism checkpoint (2 questions)
Deep-Dive: Reaction Pattern Table
Use this table as a rapid decision grid.
| Reagents | Conditions / Mechanistic Trigger | Product Pattern | Why it works |
|---|---|---|---|
| HBr, ROOR | radical addition to alkene | anti-Markovnikov bromoalkane | chain process with Br· |
| AIBN initiator | radical generation | chain starts under heat | common azo initiator |
| thiol-ene conditions | radical addition | anti-Markovnikov thioether | useful click-like transformation |
| Br2, hν | radical halogenation | alkyl bromide at most substituted site | Br· is selective |
### Fast interpretation protocol
1. Map reagent set to mechanism family.
2. Apply regio- or stereochemical rule attached to that family.
3. Check whether rearrangement, equilibration, or reversibility changes the major product call.
Input Practice — enter exact chemistry terms
1) Term for: steps that consume and regenerate radicals
2) Term for: radical-radical combination removing chain carriers
3) Product pattern expected under HBr, ROOR
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Radical inhibitors can suppress chain length and conversion.
- Initiation is usually short; propagation controls product distribution.
- Bromination is slower but more selective than chlorination.
### High-yield exam sequence
1. **Read reagents before substrate details** to classify mechanism class quickly.
2. **Mark the reactive site** (electrophilic carbon, acidic alpha-carbon, benzylic/allylic position, or aromatic position).
3. **Commit to one major-product logic path** before checking answer choices.
4. **Audit stereochemistry and regiochemistry last** so you do not lose points on orientation errors.
### Timing technique
If two options differ only by orientation or placement, spend 10 seconds restating the governing rule out loud (Markovnikov, anti addition, kinetic control, etc.) before selecting.
Applied synthesis/mechanism check (2 questions)
Part 5: Radical Stability
Radical Reactions
**Part 5 of 7 — Radical Additions to Alkenes**
This part focuses on applying peroxide-initiated additions to alkenes. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **termination**: radical-radical combination removing chain carriers
- **radical stability**: tertiary and resonance-stabilized radicals are favored
- **allylic radical**: radical adjacent to C=C with resonance support
- **NBS bromination**: allylic/benzylic bromination under radical conditions
### Worked reaction example
A representative transformation uses **AIBN initiator**.
1. Identify the governing mechanism: **radical generation**.
2. Predict the dominant product pattern: **chain starts under heat**.
3. Justify with a mechanistic note: common azo initiator.
Exam tip: state mechanism class before drawing product. It reduces avoidable regio- and stereochemistry errors.
Mechanism checkpoint (2 questions)
Deep-Dive: Reaction Pattern Table
Use this table as a rapid decision grid.
| Reagents | Conditions / Mechanistic Trigger | Product Pattern | Why it works |
|---|---|---|---|
| AIBN initiator | radical generation | chain starts under heat | common azo initiator |
| thiol-ene conditions | radical addition | anti-Markovnikov thioether | useful click-like transformation |
| Br2, hν | radical halogenation | alkyl bromide at most substituted site | Br· is selective |
| Cl2, hν | radical chlorination | mixture of chlorinated products | less selective than bromination |
### Fast interpretation protocol
1. Map reagent set to mechanism family.
2. Apply regio- or stereochemical rule attached to that family.
3. Check whether rearrangement, equilibration, or reversibility changes the major product call.
Input Practice — enter exact chemistry terms
1) Term for: radical-radical combination removing chain carriers
2) Term for: tertiary and resonance-stabilized radicals are favored
3) Product pattern expected under AIBN initiator
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Initiation is usually short; propagation controls product distribution.
- Bromination is slower but more selective than chlorination.
- Peroxide effect is classically reliable for HBr, not broadly all HX.
### High-yield exam sequence
1. **Read reagents before substrate details** to classify mechanism class quickly.
2. **Mark the reactive site** (electrophilic carbon, acidic alpha-carbon, benzylic/allylic position, or aromatic position).
3. **Commit to one major-product logic path** before checking answer choices.
4. **Audit stereochemistry and regiochemistry last** so you do not lose points on orientation errors.
### Timing technique
If two options differ only by orientation or placement, spend 10 seconds restating the governing rule out loud (Markovnikov, anti addition, kinetic control, etc.) before selecting.
Applied synthesis/mechanism check (2 questions)
Part 6: Problem-Solving Workshop
Radical Reactions
**Part 6 of 7 — Synthesis with Radical Steps**
This part focuses on combining ionic and radical steps in synthesis planning. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **radical stability**: tertiary and resonance-stabilized radicals are favored
- **allylic radical**: radical adjacent to C=C with resonance support
- **NBS bromination**: allylic/benzylic bromination under radical conditions
- **peroxide effect**: HBr adds anti-Markovnikov via radical pathway
### Worked reaction example
A representative transformation uses **thiol-ene conditions**.
1. Identify the governing mechanism: **radical addition**.
2. Predict the dominant product pattern: **anti-Markovnikov thioether**.
3. Justify with a mechanistic note: useful click-like transformation.
Exam tip: state mechanism class before drawing product. It reduces avoidable regio- and stereochemistry errors.
Mechanism checkpoint (2 questions)
Deep-Dive: Reaction Pattern Table
Use this table as a rapid decision grid.
| Reagents | Conditions / Mechanistic Trigger | Product Pattern | Why it works |
|---|---|---|---|
| thiol-ene conditions | radical addition | anti-Markovnikov thioether | useful click-like transformation |
| Br2, hν | radical halogenation | alkyl bromide at most substituted site | Br· is selective |
| Cl2, hν | radical chlorination | mixture of chlorinated products | less selective than bromination |
| NBS, hν | allylic bromination | allylic bromide | maintains alkene position overall |
### Fast interpretation protocol
1. Map reagent set to mechanism family.
2. Apply regio- or stereochemical rule attached to that family.
3. Check whether rearrangement, equilibration, or reversibility changes the major product call.
Input Practice — enter exact chemistry terms
1) Term for: tertiary and resonance-stabilized radicals are favored
2) Term for: radical adjacent to C=C with resonance support
3) Product pattern expected under thiol-ene conditions
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Bromination is slower but more selective than chlorination.
- Peroxide effect is classically reliable for HBr, not broadly all HX.
- Radical inhibitors can suppress chain length and conversion.
### High-yield exam sequence
1. **Read reagents before substrate details** to classify mechanism class quickly.
2. **Mark the reactive site** (electrophilic carbon, acidic alpha-carbon, benzylic/allylic position, or aromatic position).
3. **Commit to one major-product logic path** before checking answer choices.
4. **Audit stereochemistry and regiochemistry last** so you do not lose points on orientation errors.
### Timing technique
If two options differ only by orientation or placement, spend 10 seconds restating the governing rule out loud (Markovnikov, anti addition, kinetic control, etc.) before selecting.
Applied synthesis/mechanism check (2 questions)
Part 7: Synthesis & Review
Radical Reactions
**Part 7 of 7 — Comprehensive Radical Review**
This part focuses on solving mechanism and selectivity mixed sets. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **allylic radical**: radical adjacent to C=C with resonance support
- **NBS bromination**: allylic/benzylic bromination under radical conditions
- **peroxide effect**: HBr adds anti-Markovnikov via radical pathway
- **homolysis**: bond cleavage giving one electron to each fragment
### Worked reaction example
A representative transformation uses **Br2, hν**.
1. Identify the governing mechanism: **radical halogenation**.
2. Predict the dominant product pattern: **alkyl bromide at most substituted site**.
3. Justify with a mechanistic note: Br· is selective.
Exam tip: state mechanism class before drawing product. It reduces avoidable regio- and stereochemistry errors.
Mechanism checkpoint (2 questions)
Deep-Dive: Reaction Pattern Table
Use this table as a rapid decision grid.
| Reagents | Conditions / Mechanistic Trigger | Product Pattern | Why it works |
|---|---|---|---|
| Br2, hν | radical halogenation | alkyl bromide at most substituted site | Br· is selective |
| Cl2, hν | radical chlorination | mixture of chlorinated products | less selective than bromination |
| NBS, hν | allylic bromination | allylic bromide | maintains alkene position overall |
| HBr, ROOR | radical addition to alkene | anti-Markovnikov bromoalkane | chain process with Br· |
### Fast interpretation protocol
1. Map reagent set to mechanism family.
2. Apply regio- or stereochemical rule attached to that family.
3. Check whether rearrangement, equilibration, or reversibility changes the major product call.
Input Practice — enter exact chemistry terms
1) Term for: radical adjacent to C=C with resonance support
2) Term for: allylic/benzylic bromination under radical conditions
3) Product pattern expected under Br2, hν
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Peroxide effect is classically reliable for HBr, not broadly all HX.
- Radical inhibitors can suppress chain length and conversion.
- Initiation is usually short; propagation controls product distribution.
### High-yield exam sequence
1. **Read reagents before substrate details** to classify mechanism class quickly.
2. **Mark the reactive site** (electrophilic carbon, acidic alpha-carbon, benzylic/allylic position, or aromatic position).
3. **Commit to one major-product logic path** before checking answer choices.
4. **Audit stereochemistry and regiochemistry last** so you do not lose points on orientation errors.
### Timing technique
If two options differ only by orientation or placement, spend 10 seconds restating the governing rule out loud (Markovnikov, anti addition, kinetic control, etc.) before selecting.
Applied synthesis/mechanism check (2 questions)