Alkene Reactions

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)

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

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

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

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.

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.

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.