Synthetic Routes Revision notes | A-Level Chemistry CIE

Synthetic Routes

This lesson covers:

Summaries of key reactions for aliphatic compounds
Summaries of key reactions for aromatic compounds
How functional groups determine reactivity

Summary of key organic reactions for aliphatic compounds

Below is an overview of the primary types of organic reactions we've discussed for aliphatic compounds.

Flowchart illustrating key organic reactions for aliphatic compounds including alkanes, alkenes, alcohols, aldehydes, ketones, carboxylic acids, esters, amines, and nitriles.

Reaction	Reagent and conditions	Reaction type
1	Halogen, UV light	Free radical substitution
2	H₂, Ni or Pt catalyst, heat	Electrophilic addition
3	Al₂O₃ catalyst, heat	Thermal decomposition
4	Hydrogen halide or halogen	Electrophilic addition
5	NaOH in ethanol, reflux	Elimination
6	Conc. NH₃ in ethanol, heat under pressure	Nucleophilic substitution
7	KCN in ethanol, reflux	Nucleophilic substitution
8	Dilute HCl(aq)	Acid-base
9	NaOH(aq), reflux	Nucleophilic substitution
10	Hydrogen halide, PCl₃ or SOCl₂ OR KCl and conc. acid OR PCl₅ and heat	Nucleophilic substitution
11	Steam, H₃PO₄ catalyst, 300°C, 60 atm	Electrophilic addition
12	Conc. H₂SO₄ or Al₂O₃ catalyst, heat	Elimination
13	Cold, dilute acidified KMnO₄(aq)	Oxidation
14	K₂Cr₂O₇(aq) or KMnO₄(aq), H₂SO₄ catalyst, reflux	Oxidation
15	NaBH₄(aq) or LiAlH₄ in dry ether, heat	Reduction
16	K₂Cr₂O₇(aq) or KMnO₄(aq), H₂SO₄ catalyst, distill	Oxidation
17	HCN, KCN catalyst, heat	Nucleophilic addition
18	Dilute HCl(aq) or dilute NaOH(aq), reflux	Hydrolysis
19	Carboxylic acid, conc. H₂SO₄	Condensation
20	H₂O, dilute HCl(aq), heat	Hydrolysis
21	LiAlH₄ in dry ether, heat	Reduction
22	Dilute HCl(aq), heat	Hydrolysis
23	Alcohol, conc. H₂SO₄	Condensation
24	Dilute NaOH(aq)	Acid-base
25	H₂, Ni catalyst, heat OR LiAlH₄ in dry ether, heat	Reduction
26	NH₃ or amine	Nucleophilic addition-elimination
27	SOCl₂ or PCl₃ OR PCl₅ and heat	Substitution
28	H₂O	Nucleophilic addition-elimination
29	Alcohol	Nucleophilic addition-elimination

Summary of key organic reactions for aromatic compounds

Below is an overview of the primary types of organic reactions we've discussed for aromatic compounds.

Reactions of benzene

Reaction	Reagent and conditions	Reaction type
1	Cl₂, AlCl₃ catalyst	Electrophilic substitution
2	Conc. HNO₃, conc. HCl, 25-60°C	Electrophilic substitution
3	CH₃Cl, AlCl₃ catalyst, heat	Friedel-Crafts alkylation
4	CH₃COCl, AlCl₃ catalyst, heat	Friedel-Crafts acylation
5	Br₂, AlBr₃ catalyst	Electrophilic substitution
6	H₂, Ni or Pt catalyst, heat	Hydrogenation
7	Sn, conc. HCl, reflux, then NaOH_(aq)	Reduction
8	HNO_2(aq) or NaNO_2(s) and dilute HCl_(aq), below 10°C	Diazotisation
9	Br_2(aq)	Electrophilic substitution
10	Phenol, NaOH_(aq), below 10°C	Electrophilic substitution
11	H₂O_(l), warm	Hydrolysis
12	Cl₂, AlCl₃ catalyst	Electrophilic substitution
13	Hot, alkaline KMnO_4(aq), dilute acid	Oxidation

Reactions of phenol

Diagram showing key organic reactions for aromatic compounds including reactions of benzene and phenol.

Importance of functional groups

Functional groups are responsible for a molecule's chemical properties and reactivity. Organic molecules are categorised by homologous series based on their functional groups.

Some properties and typical reactions associated with key functional groups are:

Homologous series	Functional group	Properties	Typical reactions
Halogenoalkane	C-X	Polar bond	Nucleophilic substitution, elimination, Friedel-Crafts alkylation
Nitrile	C≡N	Electron deficient C	Reduction, hydrolysis
Hydroxynitrile	R₂C(OH)C≡N	Electron deficient C	Reduction, hydrolysis
Carboxylic acid	-COOH	Electron deficient C	Neutralisation, condensation, reduction, substitution
Amine	C–NR₂	Lone pair on nitrogen is basic and can act as a nucleophile	Neutralisation, nucleophilic substitution
Amide	RCONHR’	Electron deficient C	Hydrolysis, reduction
Aromatic compounds	C₆H₅-	Stable delocalised ring of electrons	Electrophilic substitution
Acyl chloride	-COCl	Electron deficient C	Nucleophilic addition-elimination, Friedel-Crafts acylation

So by recognising functional groups, organic chemists can predict the likely behaviour and reactivity of compounds. This allows them to design effective syntheses.