📋 Complete Reaction Reference
| Substrate | Reaction | Reagent(s) | Conditions | Product(s) | Type |
|---|---|---|---|---|---|
| Alkanes | |||||
| Alkane | Combustion (complete) | O₂ (excess) | Excess oxygen, ignition | CO₂ + H₂O | Combustion |
| Alkane | Combustion (incomplete) | O₂ (limited) | Limited oxygen | CO + C (soot) + H₂O | Combustion |
| Alkane | Free radical substitution | Halogen (Cl₂ or Br₂) | UV light | Halogenoalkane + HX | Free Radical Sub. |
| Alkenes | |||||
| Alkene | Addition of HBr / HCl | HBr(g) or HCl(g) | Room temperature, gas or conc. acid | Halogenoalkane | Electrophilic Add. |
| Alkene | Bromination | Br₂ | Br₂(l) or Br₂(aq), room temp | Dibromoalkane | Electrophilic Add. |
| Alkene | Hydration (→ alcohol) | Steam (H₂O(g)), H₃PO₄ | Heat, conc. H₃PO₄ catalyst | Alcohol | Electrophilic Add. |
| Alkene | Hydrogenation (→ alkane) | H₂(g), Ni catalyst | ~150 °C, Ni(s) catalyst | Alkane | Addition / Hydrogenation |
| Alkene | Oxidation → diol | Dilute KMnO₄ | Cold, acidic | Diol | Oxidation |
| Alkene | Oxidation → cleavage | Conc. KMnO₄ | Hot, acidic | Two carbonyl compounds | Oxidation |
| Alkene | Polymerisation | — | High pressure, catalyst | Poly(alkene) | Addition Polymerisation |
| Halogenoalkanes | |||||
| Halogenoalkane | Substitution → alcohol | NaOH (for OH⁻) | Heat under reflux, aqueous | Alcohol + halide ion | Nucleophilic Sub. |
| Halogenoalkane | Substitution → nitrile | KCN or NaCN | Heat under reflux, ethanolic | Nitrile + halide ion | Nucleophilic Sub. |
| Halogenoalkane | Substitution → amine | Excess NH₃ | Heat, ethanolic, sealed tube | Amine + ammonium halide | Nucleophilic Sub. |
| Halogenoalkane | Elimination → alkene | KOH (for OH⁻) | Heat under reflux, ethanolic | Alkene + KX + H₂O | Elimination |
| Alcohols | |||||
| Primary alcohol | Oxidation → aldehyde | K₂Cr₂O₇ / H₂SO₄ (acidified dichromate) | Heat gently, distil immediately | Aldehyde | Oxidation |
| Primary alcohol | Oxidation → carboxylic acid | K₂Cr₂O₇ / H₂SO₄ (excess) | Heat under reflux | Carboxylic acid | Oxidation |
| Secondary alcohol | Oxidation → ketone | K₂Cr₂O₇ / H₂SO₄ | Heat | Ketone (no further oxidation) | Oxidation |
| Alcohol | Elimination → alkene | Conc. H₂SO₄ or H₃PO₄ | Heat, acid catalyst | Alkene + H₂O | Elimination / Dehydration |
| Alcohol | Halogenation (PCl₅) | PCl₅(s) | Pure / dry alcohol (no water) | Chloroalkane + HCl(g) + POCl₃ | Halogenation |
| Alcohol | Halogenation (KBr) | KBr + conc. H₂SO₄ | Warm, distil product | Bromoalkane + H₂O | Halogenation |
| Alcohol | React with sodium | Na(s) | Room temperature | Alkoxide (RO⁻Na⁺) + H₂ | Acid–metal reaction |
| Alcohol + carboxylic acid | Esterification | Conc. H₂SO₄ (catalyst) | Heat under reflux | Ester + H₂O | Condensation |
| Aldehydes & Ketones | |||||
| Aldehyde | Reduction → primary alcohol | NaBH₄ | Aqueous, room temperature | Primary alcohol | Reduction |
| Ketone | Reduction → secondary alcohol | NaBH₄ | Aqueous, room temperature | Secondary alcohol | Reduction |
| Carbonyl (aldehyde or ketone) | Nucleophilic addition → hydroxynitrile | KCN (in dilute acid, H₂SO₄) | Aqueous / acidic | Hydroxynitrile | Nucleophilic Add. |
| Carboxylic Acids | |||||
| Carboxylic acid | Acid–base (with metal) | Metal (e.g. Zn, Mg) | Room temperature | Metal carboxylate + H₂ | Acid–base |
| Carboxylic acid | Acid–base (with alkali) | NaOH | Room temperature | Sodium carboxylate + H₂O | Acid–base / Neutralisation |
| Carboxylic acid | Acid–base (with carbonate) | CaCO₃ or Na₂CO₃ | Room temperature | Carboxylate salt + H₂O + CO₂ | Acid–base |
| Carboxylic acid | Reduction → primary alcohol | LiAlH₄ | Dry ether, room temperature | Primary alcohol | Reduction |
| Esters & Nitriles | |||||
| Ester | Hydrolysis (acid) | Dilute H⁺ (e.g. HCl or H₂SO₄) | Warm, aqueous | Carboxylic acid + alcohol | Hydrolysis |
| Ester | Hydrolysis (alkaline) | NaOH(aq) | Warm, aqueous | Carboxylate salt + alcohol | Hydrolysis |
| Nitrile | Acid hydrolysis → carboxylic acid | Dilute HCl | Heat under reflux | Carboxylic acid + NH₄Cl | Hydrolysis |
| Nitrile | Reduction → amine | LiAlH₄ | Dry ether | Primary amine | Reduction |
⚠ Confusable Pairs — The Conditions That Change Everything
→ Alcohol
Reagent: NaOH
Solvent: Aqueous (water present)
Conditions: Heat under reflux
Nucleophilic Substitution
→ Alkene
Reagent: KOH
Solvent: Ethanolic (no water)
Conditions: Heat under reflux
Elimination
→ Diol
KMnO₄: Dilute
Temp: Cold
Colour: Purple → colourless
Double bond intact (diol)
→ C=C Cleavage
KMnO₄: Concentrated
Temp: Hot
Products: Two carbonyl molecules
Double bond broken
→ Aldehyde
Reagent: K₂Cr₂O₇ / H₂SO₄
Method: Heat gently + distil immediately
Colour: Orange → green
Remove product before further oxidation
→ Carboxylic Acid
Reagent: K₂Cr₂O₇ / H₂SO₄ (excess)
Method: Heat under reflux
Colour: Orange → green
Keep product in flask for full oxidation
NaBH₄
Use for: Aldehydes & Ketones
Solvent: Aqueous
Safety: Mild, manageable
Aldehyde → 1° alcohol | Ketone → 2° alcohol
LiAlH₄
Use for: Carboxylic acids (+ amides, nitriles, esters)
Solvent: Dry ether (NO water)
Safety: Reacts violently with water
Carboxylic acid / nitrile → 1° alcohol / amine
Aqueous → OH⁻ wins
Nucleophile: OH⁻ (NaOH/aq)
Solvent: Water
Substitution → Alcohol
Ethanolic → Elimination favoured
Nucleophile: OH⁻ (KOH/ethanol)
Solvent: Ethanol (no water)
Elimination → Alkene
→ Alkene (dehydration)
Reactants: Alcohol only
Catalyst: Conc. H₂SO₄ or H₃PO₄
Conditions: Heat
Elimination — water lost
→ Ester (esterification)
Reactants: Alcohol + carboxylic acid
Catalyst: Conc. H₂SO₄
Conditions: Heat under reflux
Condensation — water lost + ester formed
🧠 Memory Aids
Solvent Tells You the Product
Aqueous → Alcohol (substitution)
Ethanolic → Elimination (alkene) or nitrile / amine
The first letter of the solvent matches the first letter of the product type.
KMnO₄ — Temperature Decides
Cold + dilute → Gentle → Diol (adds OH groups)
Hot + conc. → Harsh → Splits the C=C completely
FRS — Three Steps to Remember
Initiation — UV splits X₂ → 2X•
Propagation — chain reaction (×2 steps)
Termination — two radicals combine
"I Prevent Trouble"
Alcohol Oxidation — Method Matters
Distil → stop at aldehyde (remove before further reaction)
Reflux → go all the way to carboxylic acid
Same reagent (K₂Cr₂O₇/H⁺) — procedure controls product.
Halide Reactivity Order
C–F > C–Cl > C–Br > C–I
Bond strength decreases ↓ → Rate of reaction increases ↑
Iodo-compounds react fastest with nucleophiles (weakest C–X bond).
Testing for Functional Groups
Alkene: bromine water orange → colourless
Alkene (alt): acidic KMnO₄ purple → colourless
Alcohol: PCl₅ → misty white fumes of HCl
Halide speed: AgNO₃(aq) → Cl=white, Br=cream, I=yellow ppt