Amines

Write IUPAC names of the following compounds and classify them into primary, secondary and tertiary amines. (i) (CH3​)2​CHNH2​ (ii) CH3​(CH2​)2​NH2​ (iii) CH3​NHCH(CH3​)2​ (iv) (CH3​)3​CNH2​ (v) C6​H5​NHCH3​ (vi) (CH3​CH2​)2​NCH3​ (vii) m–BrC6​H4​NH2​

Give one chemical test to distinguish between the following pairs of compounds. (i) Methylamine and dimethylamine (ii) Secondary and tertiary amines (iii) Ethylamine and aniline (iv) Aniline and benzylamine (v) Aniline and N-methylaniline.

Account for the following: (i) pKb of aniline is more than that of methylamine. (ii) Ethylamine is soluble in water whereas aniline is not. (iii) Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide. (iv) Although amino group is o– and p– directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline. (v) Aniline does not undergo Friedel-Crafts reaction. (vi) Diazonium salts of aromatic amines are more stable than those of aliphatic amines. (vii) Gabriel phthalimide synthesis is preferred for synthesising primary amines.

Arrange the following: (i) In decreasing order of the pKb values: C2​H5​NH2​, C6​H5​NHCH3​, (C2​H5​)2​NH and C6​H5​NH2​ (ii) In increasing order of basic strength: C6​H5​NH2​, C6​H5​N(CH3​)2​, (C2​H5​)2​NH and CH3​NH2​ (iii) In increasing order of basic strength: (a) Aniline, p-nitroaniline and p-toluidine (b) C6​H5​NH2​, C6​H5​NHCH3​, C6​H5​CH2​NH2​. (iv) In decreasing order of basic strength in gas phase: C2​H5​NH2​, (C2​H5​)2​NH, (C2​H5​)3​N and NH3​ (v) In increasing order of boiling point: C2​H5​OH, (CH3​)2​NH, C2​H5​NH2​ (vi) In increasing order of solubility in water: C6​H5​NH2​, (C2​H5​)2​NH, C2​H5​NH2​.

How will you convert: (i) Ethanoic acid into methanamine (ii) Hexanenitrile into 1-aminopentane (iii) Methanol to ethanoic acid (iv) Ethanamine into methanamine (v) Ethanoic acid into propanoic acid (vi) Methanamine into ethanamine (vii) Nitromethane into dimethylamine (viii) Propanoic acid into ethanoic acid?

Describe a method for the identification of primary, secondary and tertiary amines. Also write chemical equations of the reactions involved.

Write short notes on the following: (i) Carbylamine reaction (ii) Diazotisation (iii) Hofmann’s bromamide reaction (iv) Coupling reaction (v) Ammonolysis (vi) Acetylation (vii) Gabriel phthalimide synthesis.

Accomplish the following conversions: (i) Nitrobenzene to benzoic acid (ii) Benzene to m-bromophenol (iii) Benzoic acid to aniline (iv) Aniline to 2,4,6-tribromofluorobenzene (v) Benzyl chloride to 2-phenylethanamine (vi) Chlorobenzene to p-chloroaniline (vii) Aniline to p-bromoaniline (viii) Benzamide to toluene (ix) Aniline to benzyl alcohol.

Give the structures of A, B and C in the following reactions: (i) CH3​CH2​INaCN​AOH−/Partialhydrolysis​BNaOH+Br2​​C (ii) C6​H5​N2​ClCuCN​AH2​O/H+​BNH3​/Δ​C (iii) CH3​CH2​BrKCN​ALiAlH4​​BHNO2​,0∘C​C (iv) C6​H5​NO2​Fe/HCl​ANaNO2​+HCl,273K​BH2​O/H+,Δ​C (v) CH3​COOHNH3​/Δ​ANaOBr​BNaNO2​/HCl​C (vi) C6​H5​NO2​Fe/HCl​AHNO2​,273K​BC6​H5​OH​C

An aromatic compound ‘A’ on treatment with aqueous ammonia and heating forms compound ‘B’ which on heating with Br2​ and KOH forms a compound ‘C’ of molecular formula C6​H7​N. Write the structures and IUPAC names of compounds A, B and C.

Complete the following reactions: (i) C6​H5​NH2​+CHCl3​+alc.KOH→ (ii) C6​H5​N2​Cl+H3​PO2​+H2​O→ (iii) C6​H5​NH2​+H2​SO4​(conc.)→ (iv) C6​H5​N2​Cl+C2​H5​OH→ (v) C6​H5​NH2​+Br2​(aq)→ (vi) C6​H5​NH2​+(CH3​CO)2​O→ (vii) $C_{6}H_{5}N_{2}Cl \xrightarrow{(i)HBF_{4} (ii)NaNO_{2}/Cu, \Delta} $

Why cannot aromatic primary amines be prepared by Gabriel phthalimide synthesis?

Write the reactions of (i) aromatic and (ii) aliphatic primary amines with nitrous acid.

Give plausible explanation for each of the following: (i) Why are amines less acidic than alcohols of comparable molecular masses? (ii) Why do primary amines have higher boiling point than tertiary amines? (iii) Why are aliphatic amines stronger bases than aromatic amines?