Radical Reactions

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)

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.

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.

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.

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.

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

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.