Oxidising agents
| Reagent | What it does |
|---|---|
| K₂Cr₂O₇ / H₂SO₄ (acidified dichromate) | Primary alcohol → aldehyde (distil) or carboxylic acid (reflux). Secondary alcohol → ketone. Orange → green. |
| PCC, CH₂Cl₂ | Primary alcohol → aldehyde (stops there). Secondary → ketone. |
| KMnO₄, cold and dilute | Alkene → diol (syn addition of two OH). |
| KMnO₄, hot | Cleaves C=C; oxidises alkyl side chains on benzene to COOH. |
| O₃, then Zn/H₂O or (CH₃)₂S | Ozonolysis: cuts C=C into two C=O compounds. |
| mCPBA | Alkene → epoxide. |
| Tollens' reagent [Ag(NH₃)₂]⁺ | Oxidises aldehydes (silver mirror); no reaction with ketones. |
Reducing agents
| Reagent | What it does |
|---|---|
| NaBH₄ | Aldehyde → primary alcohol; ketone → secondary alcohol. Doesn't reduce esters, acids or C=C. |
| LiAlH₄, then H₂O | Also reduces esters and carboxylic acids (→ primary alcohols), amides and nitriles (→ amines). |
| H₂, Pd/C (or Pt, Ni) | C=C and C≡C → alkane. |
| H₂, Lindlar catalyst | Alkyne → cis (Z) alkene. |
| Na, NH₃(l) | Alkyne → trans (E) alkene. |
| Sn, conc. HCl, then NaOH | Nitrobenzene → phenylamine. |
Adding to alkenes
| Reagent | Product |
|---|---|
| HBr | Bromoalkane, Markovnikov. |
| HBr, peroxides | Bromoalkane, anti-Markovnikov. |
| Br₂ | 1,2-Dibromide, anti addition. Decolourises bromine water. |
| H₂O, H₃PO₄ or H₂SO₄ catalyst | Alcohol, Markovnikov. |
| 1. BH₃·THF 2. H₂O₂, NaOH | Alcohol, anti-Markovnikov, syn. |
Nucleophiles, bases and carbon–carbon bonds
| Reagent | What it does |
|---|---|
| NaOH(aq), warm | Haloalkane → alcohol (substitution). |
| KOH in ethanol, hot | Haloalkane → alkene (elimination). |
| KCN in ethanol | Haloalkane → nitrile (adds one carbon). |
| HCN, KCN catalyst | Aldehyde or ketone → hydroxynitrile (adds one carbon). |
| Excess NH₃ in ethanol | Haloalkane → primary amine. |
| RMgBr (Grignard), then H₃O⁺ | With methanal → primary alcohol; other aldehydes → secondary; ketones → tertiary; CO₂ → carboxylic acid. |
| Ph₃P=CHR (Wittig) | Aldehyde or ketone → alkene. |
| NaNH₂, then RX | Terminal alkyne → longer alkyne. |
| LDA | Strong, bulky base: makes enolates. |
| NaOEt or NaOMe | Strong base / nucleophile: E2 with secondary and tertiary halides; Williamson ether synthesis with primary ones. |
Changing OH and making acid derivatives
| Reagent | What it does |
|---|---|
| PBr₃ or SOCl₂ | Alcohol → bromoalkane or chloroalkane. |
| SOCl₂ (or PCl₅) | Carboxylic acid → acyl chloride. |
| ROH, conc. H₂SO₄ catalyst, heat | Carboxylic acid → ester (Fischer esterification). |
| Conc. H₂SO₄ or H₃PO₄, heat | Alcohol → alkene (dehydration). |
| NaOH(aq), heat | Ester → carboxylate + alcohol (saponification). |
Benzene
| Reagent | Product |
|---|---|
| Conc. HNO₃, conc. H₂SO₄, < 55 °C | Nitrobenzene. |
| Br₂, FeBr₃ (or AlBr₃) | Bromobenzene. |
| RCl, AlCl₃ | Alkylbenzene (Friedel–Crafts alkylation). |
| RCOCl, AlCl₃ | Aryl ketone (Friedel–Crafts acylation). |
Examples:
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