MHT-CET Chemistry · Free notes
Amines — MHT-CET Chemistry
Amines is about two questions a paper in MHT-CET Chemistry and rarely HARD — six of its 136 past-year questions. It is a chapter of orders and named reactions: the aqueous basicity order that makes the secondary amine strongest and aniline weakest, the reductions that make amines (Mendius, LiAlH₄, Sn/HCl), the two Hofmann reactions that are always confused, the tests that sort primary from secondary from tertiary, and the diazonium salt with its replacement reactions and azo coupling. Five pages in the book's order. Every PYQ is tagged.
The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.
Subtopic notes
Nomenclature and Classification of Amines
28 PYQsAn amine is primary, secondary or tertiary by how many carbon groups sit on the nitrogen (not on the carbon), simple or mixed by whether those groups match, aliphatic or aromatic by whether one is an aryl ring; IUPAC names use -amine on the longest chain with N-prefixes for the other groups.
Physical Properties of Amines
10 PYQsPrimary and secondary amines hydrogen-bond through N–H, tertiary amines cannot; so boiling points run primary > secondary > tertiary among isomers, amines sit below alcohols and far below carboxylic acids, and water solubility runs alcohol > amine > alkane.
Preparation of Amines
32 PYQsAmines are made by reducing nitriles (Mendius, Na/ethanol, one carbon MORE than the halide), amides (LiAlH₄, same carbons) and nitro compounds (Sn/HCl), by the Hofmann bromamide degradation of an amide (one carbon FEWER) and by Gabriel phthalimide synthesis (primary only), or by ammonolysis and alkylation of halides.
Chemical Reactions and Basicity of Amines
44 PYQsAmines are bases — in water the secondary alkylamine is strongest and aniline weakest, so pKb runs the other way — and their reactions sort them by degree: acylation and the Hinsberg test need an N–H, the carbylamine test needs NH₂, exhaustive methylation and Hofmann elimination take any amine to an alkene.
Diazonium Salts and Aromatic Amine Reactions
22 PYQsAniline with NaNO₂ and HCl at 273–278 K gives benzenediazonium chloride, whose N₂⁺ is replaced by OH (warm water), Cl or Br or CN (Sandmeyer, Cu(I) salts), F (Balz–Schiemann, HBF₄), I (KI) or H (ethanol or H₃PO₂) — and which couples with phenol in mild alkali to give the azo dye p-hydroxyazobenzene.
Formula & revision sheet
10 formulas · 10 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
10 formulas · 10 gotchas across all subtopics — the exam-eve cheat-sheet
Formulas (2)
Watch out for (2)
- Grading the amine by its carbon→ Primary, Secondary, Tertiary; Simple and Mixed; Aliphatic and Aromatic
- Taking the ethyl as the parent chain→ IUPAC Names, N-Prefixes and Counting C₄H₁₁N Isomers
Watch out for (1)
- Ranking amines above alcohols because N is 'more basic'→ N–H Hydrogen Bonding: Boiling Point and Solubility
Formulas (2)
Watch out for (2)
- Forgetting that cyanide adds a carbon→ Reductions: Nitrile, Amide and Nitro to Amine
- Losing CO₂ (44) instead of CO (28)→ Hofmann Bromamide Degradation, Gabriel Synthesis and Ammonolysis
Formulas (3)
Watch out for (3)
- Reading pKb as basic strength→ Basicity: the Aqueous Order and pKb
- Giving the carbylamine test to a secondary amine→ Acylation, the Carbylamine Test and Hinsberg's Reagent
- Eliminating the propyl group because it is 'bigger'→ Exhaustive Methylation and Hofmann Elimination
Formulas (2)
Watch out for (2)
- Stopping at the diazonium salt→ Diazotisation and the Replacement Reactions of the Diazonium Ion
- Coupling in strong acid→ Azo Coupling: Diazonium Ion Plus Phenol or Aniline
PYQ weightage by concept
10 concepts · 136 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
10 concepts · 136 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Primary, Secondary, Tertiary; Simple and Mixed; Aliphatic and Aromatic | 12 | 9% |
| IUPAC Names, N-Prefixes and Counting C₄H₁₁N Isomers | 7 | 5% |
| Concept | PYQs | Share |
|---|---|---|
| N–H Hydrogen Bonding: Boiling Point and Solubility | 8 | 6% |
| Concept | PYQs | Share |
|---|---|---|
| Reductions: Nitrile, Amide and Nitro to Amine | 10 | 7% |
| Hofmann Bromamide Degradation, Gabriel Synthesis and Ammonolysis | 5 | 4% |
| Concept | PYQs | Share |
|---|---|---|
| Basicity: the Aqueous Order and pKb | 14 | 10% |
| Exhaustive Methylation and Hofmann Elimination | 7 | 5% |
| Acylation, the Carbylamine Test and Hinsberg's Reagent | 6 | 4% |
| Concept | PYQs | Share |
|---|---|---|
| Diazotisation and the Replacement Reactions of the Diazonium Ion | 9 | 7% |
| Azo Coupling: Diazonium Ion Plus Phenol or Aniline | 3 | 2% |
Test yourself on Amines
20 past MHT-CET questions from this chapter, timed at 18 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.