Alkene Reactions - Complete Interactive Lesson
Part 1: Alkene Structure & Stability
Alkene Reactions
**Part 1 of 7 — Electrophilic Addition Foundations**
This part focuses on predicting products from protonation-initiated alkene additions. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **pi bond nucleophile**: alkene electrons attack electrophiles in first step
- **carbocation intermediate**: planar cation that enables rearrangement risk
- **Markovnikov addition**: electrophile adds to carbon with more hydrogens first
- **anti-Markovnikov addition**: functional group ends on less substituted alkene carbon
### Worked reaction example
A representative transformation uses **HBr (no peroxides)**.
1. Identify the governing mechanism: **electrophilic addition via carbocation**.
2. Predict the dominant product pattern: **Markovnikov bromoalkane**.
3. Justify with a mechanistic note: rearrangement possible.
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 (no peroxides) | electrophilic addition via carbocation | Markovnikov bromoalkane | rearrangement possible |
| HBr, ROOR | radical chain addition | anti-Markovnikov bromoalkane | no carbocation rearrangement |
| Hg(OAc)2, H2O; NaBH4 | oxymercuration-demercuration | Markovnikov alcohol | avoids rearrangement |
| BH3·THF; H2O2, NaOH | hydroboration-oxidation | anti-Markovnikov syn alcohol | concerted hydroboration step |
### 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: alkene electrons attack electrophiles in first step
2) Term for: planar cation that enables rearrangement risk
3) Product pattern expected under HBr (no peroxides)
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Markovnikov labels regiochemistry, not stereochemistry.
- Peroxides alter HBr behavior but not HCl/HI in standard coursework.
- Syn/anti outcome depends on mechanism, not alkene substitution alone.
### 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: Electrophilic Addition
Alkene Reactions
**Part 2 of 7 — Regioselectivity: Markovnikov vs Anti-Markovnikov**
This part focuses on choosing reagent sets to control where new bonds form. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **carbocation intermediate**: planar cation that enables rearrangement risk
- **Markovnikov addition**: electrophile adds to carbon with more hydrogens first
- **anti-Markovnikov addition**: functional group ends on less substituted alkene carbon
- **syn addition**: both new groups add to same alkene face
### Worked reaction example
A representative transformation uses **HBr, ROOR**.
1. Identify the governing mechanism: **radical chain addition**.
2. Predict the dominant product pattern: **anti-Markovnikov bromoalkane**.
3. Justify with a mechanistic note: no carbocation rearrangement.
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 chain addition | anti-Markovnikov bromoalkane | no carbocation rearrangement |
| Hg(OAc)2, H2O; NaBH4 | oxymercuration-demercuration | Markovnikov alcohol | avoids rearrangement |
| BH3·THF; H2O2, NaOH | hydroboration-oxidation | anti-Markovnikov syn alcohol | concerted hydroboration step |
| Br2 in CCl4 | halonium-mediated addition | vicinal anti dibromide | ring opening from backside |
### 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: planar cation that enables rearrangement risk
2) Term for: electrophile adds to carbon with more hydrogens first
3) Product pattern expected under HBr, ROOR
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Peroxides alter HBr behavior but not HCl/HI in standard coursework.
- Syn/anti outcome depends on mechanism, not alkene substitution alone.
- Ozonolysis products come from cleavage; no intact C=C remains.
### 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: Markovnikov & Anti-Markovnikov
Alkene Reactions
**Part 3 of 7 — Stereochemical Outcomes of Addition**
This part focuses on deciding between syn and anti additions on cyclic alkenes. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **Markovnikov addition**: electrophile adds to carbon with more hydrogens first
- **anti-Markovnikov addition**: functional group ends on less substituted alkene carbon
- **syn addition**: both new groups add to same alkene face
- **anti addition**: new groups add to opposite faces
### Worked reaction example
A representative transformation uses **Hg(OAc)2, H2O; NaBH4**.
1. Identify the governing mechanism: **oxymercuration-demercuration**.
2. Predict the dominant product pattern: **Markovnikov alcohol**.
3. Justify with a mechanistic note: avoids rearrangement.
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 |
|---|---|---|---|
| Hg(OAc)2, H2O; NaBH4 | oxymercuration-demercuration | Markovnikov alcohol | avoids rearrangement |
| BH3·THF; H2O2, NaOH | hydroboration-oxidation | anti-Markovnikov syn alcohol | concerted hydroboration step |
| Br2 in CCl4 | halonium-mediated addition | vicinal anti dibromide | ring opening from backside |
| O3 then Me2S | reductive ozonolysis | aldehydes/ketones from cleavage | double bond fully fragmented |
### 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: electrophile adds to carbon with more hydrogens first
2) Term for: functional group ends on less substituted alkene carbon
3) Product pattern expected under Hg(OAc)2, H2O; NaBH4
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Syn/anti outcome depends on mechanism, not alkene substitution alone.
- Ozonolysis products come from cleavage; no intact C=C remains.
- Markovnikov labels regiochemistry, not stereochemistry.
### 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: Hydroboration-Oxidation
Alkene Reactions
**Part 4 of 7 — Oxidation and Cleavage Patterns**
This part focuses on matching oxidation level to exam product options. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **anti-Markovnikov addition**: functional group ends on less substituted alkene carbon
- **syn addition**: both new groups add to same alkene face
- **anti addition**: new groups add to opposite faces
- **osmium oxidation**: OsO4 gives vicinal syn diol
### Worked reaction example
A representative transformation uses **BH3·THF; H2O2, NaOH**.
1. Identify the governing mechanism: **hydroboration-oxidation**.
2. Predict the dominant product pattern: **anti-Markovnikov syn alcohol**.
3. Justify with a mechanistic note: concerted hydroboration step.
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 |
|---|---|---|---|
| BH3·THF; H2O2, NaOH | hydroboration-oxidation | anti-Markovnikov syn alcohol | concerted hydroboration step |
| Br2 in CCl4 | halonium-mediated addition | vicinal anti dibromide | ring opening from backside |
| O3 then Me2S | reductive ozonolysis | aldehydes/ketones from cleavage | double bond fully fragmented |
| HBr (no peroxides) | electrophilic addition via carbocation | Markovnikov bromoalkane | rearrangement possible |
### 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: functional group ends on less substituted alkene carbon
2) Term for: both new groups add to same alkene face
3) Product pattern expected under BH3·THF; H2O2, NaOH
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Ozonolysis products come from cleavage; no intact C=C remains.
- Markovnikov labels regiochemistry, not stereochemistry.
- Peroxides alter HBr behavior but not HCl/HI in standard coursework.
### 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: Oxidation & Reduction
Alkene Reactions
**Part 5 of 7 — Hydroboration and Oxymercuration Contrast**
This part focuses on contrasting carbocation pathways with concerted additions. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **syn addition**: both new groups add to same alkene face
- **anti addition**: new groups add to opposite faces
- **osmium oxidation**: OsO4 gives vicinal syn diol
- **ozonolysis**: O3 cleaves C=C into carbonyl fragments
### Worked reaction example
A representative transformation uses **Br2 in CCl4**.
1. Identify the governing mechanism: **halonium-mediated addition**.
2. Predict the dominant product pattern: **vicinal anti dibromide**.
3. Justify with a mechanistic note: ring opening from backside.
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 in CCl4 | halonium-mediated addition | vicinal anti dibromide | ring opening from backside |
| O3 then Me2S | reductive ozonolysis | aldehydes/ketones from cleavage | double bond fully fragmented |
| HBr (no peroxides) | electrophilic addition via carbocation | Markovnikov bromoalkane | rearrangement possible |
| HBr, ROOR | radical chain addition | anti-Markovnikov bromoalkane | no carbocation rearrangement |
### 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: both new groups add to same alkene face
2) Term for: new groups add to opposite faces
3) Product pattern expected under Br2 in CCl4
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Markovnikov labels regiochemistry, not stereochemistry.
- Peroxides alter HBr behavior but not HCl/HI in standard coursework.
- Syn/anti outcome depends on mechanism, not alkene substitution alone.
### 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
Alkene Reactions
**Part 6 of 7 — Synthesis Sequencing with Alkenes**
This part focuses on building two-step synthesis from an alkene intermediate. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **anti addition**: new groups add to opposite faces
- **osmium oxidation**: OsO4 gives vicinal syn diol
- **ozonolysis**: O3 cleaves C=C into carbonyl fragments
- **rearrangement**: hydride or alkyl shift to more stable carbocation
### Worked reaction example
A representative transformation uses **O3 then Me2S**.
1. Identify the governing mechanism: **reductive ozonolysis**.
2. Predict the dominant product pattern: **aldehydes/ketones from cleavage**.
3. Justify with a mechanistic note: double bond fully fragmented.
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 |
|---|---|---|---|
| O3 then Me2S | reductive ozonolysis | aldehydes/ketones from cleavage | double bond fully fragmented |
| HBr (no peroxides) | electrophilic addition via carbocation | Markovnikov bromoalkane | rearrangement possible |
| HBr, ROOR | radical chain addition | anti-Markovnikov bromoalkane | no carbocation rearrangement |
| Hg(OAc)2, H2O; NaBH4 | oxymercuration-demercuration | Markovnikov alcohol | avoids rearrangement |
### 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: new groups add to opposite faces
2) Term for: OsO4 gives vicinal syn diol
3) Product pattern expected under O3 then Me2S
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Peroxides alter HBr behavior but not HCl/HI in standard coursework.
- Syn/anti outcome depends on mechanism, not alkene substitution alone.
- Ozonolysis products come from cleavage; no intact C=C remains.
### 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
Alkene Reactions
**Part 7 of 7 — Comprehensive Product Prediction**
This part focuses on solving mixed mechanism sets under time pressure. The goal is to connect vocabulary, curved-arrow reasoning, and product prediction in one workflow.
### Mechanism vocabulary for this part
- **osmium oxidation**: OsO4 gives vicinal syn diol
- **ozonolysis**: O3 cleaves C=C into carbonyl fragments
- **rearrangement**: hydride or alkyl shift to more stable carbocation
- **pi bond nucleophile**: alkene electrons attack electrophiles in first step
### Worked reaction example
A representative transformation uses **HBr (no peroxides)**.
1. Identify the governing mechanism: **electrophilic addition via carbocation**.
2. Predict the dominant product pattern: **Markovnikov bromoalkane**.
3. Justify with a mechanistic note: rearrangement possible.
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 (no peroxides) | electrophilic addition via carbocation | Markovnikov bromoalkane | rearrangement possible |
| HBr, ROOR | radical chain addition | anti-Markovnikov bromoalkane | no carbocation rearrangement |
| Hg(OAc)2, H2O; NaBH4 | oxymercuration-demercuration | Markovnikov alcohol | avoids rearrangement |
| BH3·THF; H2O2, NaOH | hydroboration-oxidation | anti-Markovnikov syn alcohol | concerted hydroboration step |
### 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: OsO4 gives vicinal syn diol
2) Term for: O3 cleaves C=C into carbonyl fragments
3) Product pattern expected under HBr (no peroxides)
Dropdown matching (3 prompts)
Strategy: Prediction Traps and Exam Techniques
### Common traps in this part
- Syn/anti outcome depends on mechanism, not alkene substitution alone.
- Ozonolysis products come from cleavage; no intact C=C remains.
- Markovnikov labels regiochemistry, not stereochemistry.
### 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)