Amines
Class 12 · Chemistry
4 ideas in Class 12 Chemistry, explained in plain words, with games and quizzes to practise.
Amine Structure, Families and Names
Part of: Meeting the Amine Family
Amines swap one or more hydrogens of ammonia for carbon groups. One carbon on nitrogen means primary, two means secondary, three means tertiary. Everyday names stick the group before amine, while systematic names end in amine with N marking groups on nitrogen. The lone pair makes the shape pyramidal and lets primary and secondary members grip each other with hydrogen bonds.
Why it matters. The family tag predicts boiling, solubility and every later reaction, and wrong classification is the commonest error in this unit.
Formulas
- Primary amine: one carbon on nitrogen; secondary: two; tertiary: three
- Boiling order for isomers: primary above secondary above tertiary
- N-locants name groups sitting on nitrogen, not on carbon
Key words
- Primary amine
- : An amine with exactly one carbon group joined to nitrogen.
- Mixed amine
- : A secondary or tertiary amine carrying different groups on nitrogen.
- Alkanamine
- : The systematic family name for amines built on alkane chains.
- Aniline
- : Phenylamine, the simplest aromatic amine, accepted in both naming systems.
- Pyramidal geometry
- : The bent shape from three bonds plus a lone pair pushing down.
- Hydrogen bonding
- : A strong grip between an N-H or O-H hydrogen and a lone pair nearby.
Try it in two minutes
- Write five formulas and ask the child to count carbons on nitrogen.
- Sort them into primary, secondary and tertiary piles.
- Name one member from each pile in the systematic style.
Try at home. Explain why butan-1-amine boils higher than its tertiary isomer using N-H bonds.
Making Amines
Part of: Meeting the Amine Family
Nitro compounds reduce to amines with metal and acid, alkyl halides swap halogen for amino groups with ammonia, and nitriles or amides reduce to amines with LiAlH4. Gabriel synthesis delivers clean primary amines from alkyl halides, while Hoffmann degradation trims an amide down by one carbon. Nitrile reduction climbs one carbon up; Hoffmann drops one carbon down.
Why it matters. These six routes answer most conversion questions, and mixing up climb versus drop loses marks fast.
Formulas
- Nitrile reduction climbs one carbon up the amine series
- Hoffmann degradation drops one carbon from the amide
- Excess ammonia makes the primary amine the major product
Key words
- Ammonolysis
- : Cleaving a carbon-halogen bond with ammonia to plant an amino group.
- Gabriel synthesis
- : A route giving pure primary amines via a phthalimide intermediate.
- Hoffmann degradation
- : Trimming an amide to an amine with one carbon fewer using bromine and alkali.
- Nitrile reduction
- : Reducing a nitrile to a primary amine with the same carbon count.
- Amide reduction
- : Reducing an amide to an amine with the same carbon count using LiAlH4.
- Quaternary ammonium salt
- : A nitrogen holding four carbon groups with a positive charge.
Try it in two minutes
- Write a target amine and ask whether it needs more or fewer carbons.
- Pick climb for more and drop for fewer.
- Name the reagent pair for the chosen route.
Try at home. Plan ethanamide to methanamine and bromoethane to propanamine, naming each step.
Base Strength and Amine Reactions
Part of: Basicity, Reactions and Diazonium Salts
Amines grab protons with their lone pair, and a smaller pKb means a stronger base. Alkyl pushes raise strength above ammonia, while the ring in aniline hides the lone pair and sinks it below. In water, how tightly water wraps the formed ion matters more than the push, so the order differs from the gas phase. Primary amines answer carbylamine and nitrous acid tests, and Hinsberg reagent sorts all three types.
Why it matters. Basicity ranking and type tests dominate board questions, and the water-versus-gas twist rewards real understanding.
Formulas
- A smaller pKb means a stronger base
- Aniline is weaker than ammonia; alkylamines are stronger
- Acetylation tames the amino group before nitration
Key words
- pKb
- : A scale number for base strength; a smaller value means a stronger base.
- Carbylamine reaction
- : A foul-smelling test for primary amines using chloroform and alkali.
- Hinsberg reagent
- : Benzenesulphonyl chloride, used to sort primary, secondary and tertiary amines.
- Acylation
- : Swapping an N-H hydrogen for an acyl group to form an amide.
- Anilinium ion
- : Protonated aniline, which directs new groups to the meta position.
- Protecting group
- : A temporary cover, like acetyl on nitrogen, that calms a reactive group.
Try it in two minutes
- Write four amines with their pKb values on cards.
- Ask the child to order them from strongest to weakest base.
- Ask what changes if the same molecules met in the gas phase.
Try at home. Explain why p-toluidine is stronger than aniline but p-nitroaniline is weaker.
Diazonium Salts: Making and Using
Part of: Basicity, Reactions and Diazonium Salts
Primary aromatic amines turn into diazonium salts with nitrous acid near freezing point. The nitrogen pair leaves as a gas, so chlorine, bromine, iodine, cyanide, hydrogen, hydroxyl and nitro groups can all take its place with the right reagent. With phenol or aniline the diazo group stays and couples at the para position, painting bright azo dyes.
Why it matters. Many ring compounds cannot be made by direct attack, and diazonium chemistry is the back door that reaches them.
Formulas
- Diazotisation runs at 273 to 278 K with NaNO2 plus HCl
- Sandmeyer uses copper(I) salts; Gatterman uses copper powder
- Coupling with phenol or aniline strikes the para position
Key words
- Diazotisation
- : Turning a primary aromatic amine into a diazonium salt in the cold.
- Sandmeyer reaction
- : Swapping the diazo group for Cl, Br or CN using copper(I) salts.
- Gatterman reaction
- : Swapping the diazo group for Cl or Br using copper powder and acid.
- Coupling reaction
- : Joining a diazonium salt to phenol or aniline at the para position.
- Diazonium group
- : The N2 unit on a ring that leaves readily as nitrogen gas.
- Azo dye
- : A coloured compound with two rings joined through an N and N link.
Try it in two minutes
- Write aniline at the centre and list six groups around it.
- Ask the child to name the reagent that plants each group.
- Finish by pairing diazonium with phenol to draw a dye.
Try at home. Trace aniline to fluorobenzene and to p-hydroxyazobenzene, naming every reagent.
What your child will practise
- Amine Structure, Families and Names: Desert Quick Fire (Quick Fire)
- Base Strength and Amine Reactions: Space Puzzle (Clue Puzzle)
- Base Strength and Amine Reactions: Space Quick Fire (Quick Fire)
- Diazonium Salts: Making and Using: Ocean Quick Fire (Quick Fire)
- Making Amines: Jungle Puzzle (Clue Puzzle)
- Quiz: Amine Structure, Families and Names (8 questions)
- Quiz: Base Strength and Amine Reactions (8 questions)
- Quiz: Diazonium Salts: Making and Using (8 questions)
- Quiz: Making Amines (8 questions)