Write short notes on the following:
(i) Carbylamine reaction (il) Diazotisation (iii) ‘Hofmann's bromamide reaction
(iv) Coupling reaction (v) Ammonolysis (vi) Acetylation
(vii) Gabriel phthalimide synthesis
(i) Carbylamine reaction: Both aliphatic and aromatic primary amines when warmed with chloroform and an alcoholic solution of KOH, produces isocyanides or carbylamines which have very unpleasant odours. This reaction is called carbylamine reaction.
(ii)Diazotisation: The process of conversion of a primary aromatic amino compound into a diazonium salt, is known as diazotisation. This process is carried out by adding an aqueous solution of sodium nitrite to a solution of primary aromatic amine (e.g., aniline) in excess of HCl at a temperature below 5 °C.
(iii)Hoffmann's bromamide reaction: When an amide is treated with bromine in alkali solution, it is converted to a primary amine that has one carbon atom less than the starting amide. This reaction is known as Hoffinann's bromamide degradation reaction.
(iv) Coupling reaction: In this reaction, arene diazonium salt reacts with aromatic amino compound (in acidic medium) or a phenol (in alkaline medium) to form brightly coloured azo compounds. The reaction generally takes place at para position to the hydroxy or amino group. If para position is blocked, it occurs at ortho position and if both ortho and para positions are occupied, than no coupling takes place.
(v) Ammonolysis: It is a process of replacement of either halogen atom in alkyl halides (or aryl halides) or hydroxyl group in alcohols (or phenols) by amino group. The reagent used for ammonolysis is alcoholic ammonia. Generally, a mixture of primary, secondary and tertiary amine is formed.
(vi) Acetylation: The process of introducing an acetyl (CH3CO-) group into molecule using acetyl chloride or acetic anhydride is called acetylation.
(vii) Gabriel phthalimide synthesis: It is a method of preparation of pure aliphatic and aralkyl primary amines. Phthalimide on treatment with ethanolic KOH gives potassium phathalimide which on heating with a suitable alkyl Or aralkyl halides gives N-substituted phthalimides, which on hydrolysis with dil HCI or with alkali give primary amines.
Describe a method for the identification of primary, secondary and tertiary amines. Also write chemical equations of the reactions involved.
Why is benzene diazonium chloride not stored and is used immediately after its preparation?
Complete the following acid-base reactions and name the products:
(i) CH3CH2CH2NH2+HCl ——–>
(ii) (C2H5)3 N+HCl ——–>
Under which of the following reaction conditions, aniline gives p-nitro derivative as the major product?
(a) Acetyl chloride/pyridine followed by reaction with cone. H2SO4 + cone.
(b) Acetic anhydride/pyridine followed by cone. H2SO4 + cone. HNO3
(c) Dil. HCl followed by reaction with cone. H2SO4 + cone. HNO3
(d) Reaction with cone. HNO3 + cone. H2S04
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.
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?
Which of the following reactions belong to electrophilic aromatic substitution?
(a) Bromination of acetanilide
(b) Coupling reaction of aryldiazonium salts
(c) Diazotisation of aniline
(d) Acylation of aniline
Reduction of nitrobenzene by which of the following reagents give aniline?
(a) Sn/HCl (b) Fe/HCl (c) H2-Pd (d) Sn/NH4OH
Assertion (A): N, N-diethylbenzene sulphonamide is insoluble in alkalf. Reason (R): Sulphonyl group attached to nitrogen atom is strong electron withdrawing group.
Write short notes on the following:
(i) Carbylamine reaction (il) Diazotisation (iii) ‘Hofmann's bromamide reaction
(iv) Coupling reaction (v) Ammonolysis (vi) Acetylation
(vii) Gabriel phthalimide synthesis
Amongst the given set of reactants, the most appropriate for preparing 2 ° amine is .
(a) 2 ° R – Br + NH3
(b) 2 ° R – Br + NaCN followed by H2/Pt
(c) 10 R – NH2 + RCHO followed by H2/Pt
(d) 1 ° R – Br + (2 mol) + potassium phthalimide followed by H3O+/heat
The reagents that can be used to convert benzene diazonium chloride to benzene are
(a) SnCl2/HCl (b) CH3CH2OH
(c) H3PO2 (d) LiAlH4
Predict the product of reaction of aniline with bromine in non-polar solvent such as CS2.
Write following conversions:
(i) nitrobenzene –> acetanilide
(ii) acetanilide –> p-nitroaniline
Arrange the following in increasing order of their basic strength: ‘
(i) C2H5NH2,C6H5NH2,NH3,C6H5CH2NH2 and(C2H5)2 NH
(ii) C2H5NH2,(C2H5)2NH,(C2H5)3N,C6H5NH2
(iii) CH3NH2, (CH3)2NH, (CH3)3N, C6H5NH2, C6H5CH2NH2
A hydrocarbon 'A', (C4H8) on reaction with HC1 gives a compound 'B'(C4H9Cl), which on reaction with 1 mol of NH3 gives compound 'C', (C4H11N). On reacting with NaN02 and HC1 followed by treatment with water, compound 'C' yields an optically active alcohol, 'D'. Ozonolysis of 'A' gives 2 moles of acetaldehyde. Identify compounds 'A' to 'D'. Explain the reactions involved.
The correct IUPAC name for CH2 = CHCH2NHCH3 is
(a) allylmethylamine (b) 2-amino-4-pentene
(c) 4-aminopent-l-ene . (d) N-methylprop-2-en-l-amine.
Assertion (A): Acetanilide is less basic than aniline.
Reason (R): Acetylation of aniline results in decrease of electron density on nitrogen.
The best reagent for converting-2-phenylpro-panamide into 1-phenylethana- mine is .
(a) excess H2/Pt (b) NaOH /Br2
(c) NaBH4/methanol (d) LiAlH4/ether
Assertion (A): Only a small amount of HCl is required in the reduction of nitro compounds with iron scrap and HCl in the presence of steam.
Reason (R): FeCl2 formed gets hydrolysed to release HCl during the reaction.
Write the reactions of (i) aromatic and (ii) aliphatic primary amines with nitrous acid.
Which of the following is a 3 ° amine?
(a) 1 -Methylcyclohexylamine (c) tert-Butylamine
A primary amine, RNH2 can be reacted with CH3-X to get secondary amine, R NHCH3 but the only disadvantage is that 3 ° amine and quaternary ammonium salts are also obtained as side products. Can you suggest a method where RNH2 forms only 2 ° amine?
Assertion (A): N-Ethylbenzene sulphonamide is soluble in alkali.
Reason (R): Hydrogen attached to nitrogen in sulphonamide is strongly acidic.
(i)Write the structures of different isomeric amines corresponding to the molecular formula, C4H11N.
(ii)Write 1UPAC names of all the isomers.
(iii)What type of isomerism is exhibited by different pairs of amines?
Write structures of different isomers corresponding to the molecular formula, C3H9N. Write IUPAC names of the isomers which will liberated N2 gas on treatment with nitrons acid.
Convert:
(i) 3-Methylanilineinto3-nitrotoluene
(ii) Aniline into 1,3,5- Tribromo benzene
How wjll 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?
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?
Assertion (A): Hofmann's bromamide reaction is given by primary amines. Reason (R): Primary amines are more basic than secondary amines.
Which of the following cannot be prepared by Sandmeyer's reaction?
(a) Chlorobenzene (b) Bromobenzene
(c) Iodobenzene (d) Fluorobenzene
Which of the following amines can be prepared by Gabriel synthesis?
(a) Isobutyl amine (b) 2-Phenylethylamine
(c) N-Methylbenzylamine (d) Aniline
