CBSE Class 12 Chemistry HOTs Animes

VERY SHORT ANSWER TYPE QUESTIONS 

Question. Write IUPAC name of CH₃NC.
Answer. Methane carbylamine.

Question. Convert m-dinitrobenzene to m-nitro aniline.
Answer.

Question. Draw structure of TNT, an explosive.
Answer.

Question. Write IUPAC name of

Answer. 3-Methyl-N,N-dimethyl pentanamine

Question. Give one use of quaternary ammonium salts.
Answer. It is used as detergents, e.g., [CH₃(CH₂)₁₅N(CH₃)₂]⁺Cl⁻.

Question. What is Hinsberg’s reagent ?
Answer. Benzene sulphonyl chloride,

Question. Why aniline dissolves in HCl ?
Answer. C₆H₅NH₂ + HCl → [C₆H₅NH₃]⁺Cl⁻.
It dissolves due to its basic nature.

Question. How will you test the presence of primary amine ?
Answer. By carbyl amine test.
RNH₂ + CHCl₃ + 3KOH → R—NC + 3KCl + 3H₂O

Question. What is vapour phase nitration ?
Answer.

(High temperature and nitration in vapour phase only)

Question. Write one use of dopamine and atropine alkaloid.
Answer. Dopamine : Neurotransmitter
Atropine alkaloid : 0.5-1.0% solution ophthalmic examination.

Question. Direct nitration of aniline is not carried out. Explain.
Answer. (H₂SO₄ + HNO₃) easily oxidized aniline into tarry complex product due to high e− density on the benzene ring of aniline.

Question. Among the compounds as following which will react with

to give product containing > C = N − ?
(i) C₆H₅NH₂            (ii) (CH₃)₃N
(iii) C₆H₅NHC₆H₅    (iv) C₆H₅NHNH₂
Answer. C₆H₅NH₂ and C₆H₅NHNH₂.

Question. How will you give expression for Kb to indicate its basic strength ?
Answer.

Question. What happens when aniline is treated with bromine ?
Answer.

Question. Write a chemical equation to illustrate the ammonolysis.
Answer. For alcohols :

Question. Write the structure of p-toluidine.
Answer.

Question. Prepare/convert nitrobenzene into aniline.
Answer.

Question. Convert C₆H₅COOH to C₆H₅NH₂.
Answer.

Question. Write isomerism exhibited by different amines.
Answer. Chain, position, metamerism, functional.

Question. Arrange the following compounds in increasing order of solubility in water:
C₆H₅NH₂, (C₂H₅)₂NH, C₂H₅NH₂
Answer. C₆H₅NH₂ < (C₂H₅)₂NH< C₂H₅NH₂

SHORT ANSWER TYPE QUESTIONS 

Question. Complete the following acid-base reactions and name the products :
(i) CH₃CH₂CH₂NH₂ + HCl →
(ii) (CH₃CH₂)₃N + HCl →
Answer. (i) CH₃CH₂CH₂N+H₃Cl− (n-propyl ammonium chloride)
(ii) (CH₃CH₂)₃ – N+HCl− (Triethyl ammonium chloride)

Question. Write chemical reaction of C₆H₅NH₂ + C₆H₅COCl and name product obtained.
Answer.

Question. How will you convert :
(i) 3-methylaniline → 3-nitrotoluene
(ii) Aniline → 1, 3, 5-tribromobenzene
Answer.

Question. How will you convert :
(i) Propanoic acid → Ethanoic acid
(ii) Nitromethane → Dimethylamine
Answer.

Question. Draw the structures of the following compounds :
(i) N-isopropylaniline (ii) t-butylamine
Answer.

Question. Why C₆H₅N+(CH₃)₃OH− a stronger base than NH₄OH ?
Answer. Due to – I effect of phenyl group, it decreases e− density on nitrogen atom but no such group in NH4OH.

Question. Explain Kb order : Et₂NH > Et₃N > EtNH₂ in aqueous solution.
Answer. Basicity of amines in aqueous solution depends upon :
(i) + I effect of an alkyl group.
(ii) Extent of hydrogen bonding with H₂O.
(iii) Steric effects of alkyl groups.

Question. Distinguish between 1º, 2º and 3º amines by HNO₂ acid test.
Answer. 1º gives N₂ gas. 2º gives yellow oily compound. 3º form water soluble salts.
CH₃CH₂NH₂ + HNO₂ → C₂H₅OH + N₂ + H₂O
R₂NH + HNO₂ → R₂N – N = O + H₂O

Question. A compound ‘A’ having molecular formula C₃H₇ON reacts with Br₂ in presence of NaOH to give compound ‘B’. This compound ‘B’ reacts with HNO₂ to form alcohol and N₂ gas. Identify compound ‘A’ and ‘B’ and write the reaction involved.
Answer.

 

Question. Write chemical equation for the following conversions :
(i) CH₃ − CH₂ – Cl → CH₂ – CH₂ – CH₂ – NH₂
(ii) C₆H₅ – CH₂ – Cl → C₆H₅CH₂CH₂ – NH₂
Answer. (i) With NaCN and reduction

Question. Account for :
(i) Amino group in aniline is o- and p- directing in aromatic electrophilic substitution reactions. Aniline on nitration gives a substantial amount of m-nitroaniline.
(ii) Aniline does not go Friedel Crafts reaction.
Answer. (i) It is because aniline is protonated to form anilinium cation, in which NH₃ group is meta-directing..
(ii) It is because aniline is basic, can form adduct with AlCl₃, electrophile cannot be generated.

Question. Account for the following :
(i) Electrophilic substitution in aromatic amines takes place more readily than benzene.
(ii) Nitro compounds have higher boiling points than hydrocarbons having almost same molecular mass.
Answer. (i) –NH₂ is ERG, electrophilic substitution takes place faster.
(ii) Nitro compounds are more polar than hydrocarbons therefore have more van der Waal’s forces of attraction.

Question. Write short notes on :
(i) Coupling reaction
(ii) Ammonolysis
Answer.

Question. Prepare pure sample of 1º amine from 1º alkyl halide.
Answer. By Gabriel Phthalimide Reaction

SHORT ANSWER TYPE QUESTIONS 

Question. What happens when :
(i) An alkyl halide reacts with AgNO₂ and product is reduced.
(ii) An alkyl halide is treated with AgCN and product is hydrolysed.
(iii) Methyl magnesium is treated with cyanogens chloride.
Answer.

Question. How would you prepare :
(i) C₆H₅NH₂ from C₆H₅NO₂
(ii) CH₃NH₂ from C₂H₅NH₂
(iii) C₂H₅NH₂ from CH₃NH₂
Answer.

Question. Write the structure of the products in each case :

Answer. (i) CH₃CH₂NHCOCH₃, CH₃COOH

(iii) CH₃CH₂COOH + NH₄⁺

Question. Write the structures of A, B and C in following

Answer. (i) C₆H₅NH₂ ,C₆H₅N₂⁺Cl⁻ ,C₆H₅I 
(ii) CH₃CN, CH₃CH₂NH₂, CH₃CH₂NC

Question. Write the structure of reagents/organic compounds ‘A’ to ‘F’ :
Answer.

LONG ANSWER TYPE QUESTIONS 

Question. Arrange the following :
(i) In decreasing order of pKb values :
C₂H₅NH₂, C₆H₅NHCH₃, (C₂H₅)₂NH and C₆H₅NH₂
(ii) In increasing order of basic strength :
(a) Aniline, p-nitroaniline and p-toluidine
(b) C₆H₅NH₂, C₆H₅NHCH₃, C₆H₅CH₂NH₂
(iii) In decreasing order of basic strength :
C₆H₅NH₂, C₆H₅N(CH₃)₂, (C₂H₅)₂NH, CH₃NH₂
(iv) Decreasing order of basic strength in gas phase :
C₂H₅NH₂, (C₂H₅)₂NH, (C₂H₅)₃N and NH₃
(v) Increasing order of boiling point :
C₂H₅OH, (CH₃)₂NH,C₂H₅NH₂
Answer. (i) C₆H₅NH₂ > C₆H₅NHCH₃ > C₂H₅NH₂ > (C₂H₅)₂NH
(ii) (a) p-nitroaniline < aniline < p-toluidine
(b) C₆H₅NH₂ < C₆H₅NHCH₃ < C₆H₅CH₂NH₂
(iii) (C₂H₅)₂NH > CH₃NH₂ > C₆H₅N(CH₃)₂ > C₆H₅NH₂
(iv) (C₂H₅)₃N > (C₂H₅)₂NH > C₂H₅NH₂ > NH₃
(v) (CH₃)₂NH < C₂H₅NH₂ < C₂H₅OH

Question. How will you convert :
(i) Ethanoic acid into methanamine
(ii) Hexane nitrile into 1-aminopentane
(iii) Methanol into ethanoic acid
(iv) Ethanamine into methanamine
Answer.

Question. Write short note on the following :
(i) Carbylamine reaction
(ii) Diazotization
(iii) Hoffmann’s bromide reaction
(iv) Coupling reaction
(v) Ammonolysis
Answer. (i) Carbylamine reaction : When primary amine (aromatic or aliphatic) warmed with chloroform and alc. KOH, isocyanides are formed which can be identified by their offensive smell. This test is used to identify the presence of primary amine or chloroform.

(b) Diazotization : When primary aromatic amine is treated with NaNO₂ and HCl at 273-278 K, diazonium salt is obtained. This reaction is known as diazotization.

Benzenediazonium chloride is a very important synthetic compound, which can be changed into heloarenes, phenol, cyanobenzene, benzene etc.

(c) Hoffmann’s bromide reaction : When any primary amide (aliphatic or aromatic) is treated with bromine and alkali, it gives the amine with one less carbon atom.

This reaction is used to reduce one carbon atom from a compound.
(d) Coupling reaction : When benzenediazonium chloride is treated with phenols or aromatic amines, azo dyes are produced in which diazo
(− N = N −) group is retained. Coupling reactions generally take place at p-position of phenol or aromatic amines.

(e) Ammonolysis : Reaction of alkyl halides with ammonia is known as ammonolysis. Ammonolysis generally gives the mixture of 1º, 2º, 3º amines and quaternary ammonium salt.

Question. Complete the following reactions :
(i) C₆H₅NH₂ + H₂SO₄ (conc.) →
(ii) C₆H₅N₂Cl + C₂H₅OH →
(iii) C₆H₅NH₂ + (CH₃CO)₂O →
(iv) C₆H₅N₂Cl + H₃PO₂ + H₂O →
(v) C₆H₅NH₂ + CHCl₃ + 3KOH (alc.) →
Answer.

(ii) C₆H₆ + N₂ + HCl + CH₃CHO
(iii) C₆H₅NHCOCH₃ + CH₃COOH
(iv) C₆H₆ + H₃PO₃ + HCl + N₂
(v) C₆H₅NC + 3KCl + 3H₂O

Question. Write A, B and C in the given reactions :

Answer.

Question. Accomplish the following conversions :
(i) C₆H₅NO₂ → C₆H₅ – COOH
(ii) Benzene → m-bromophenol
(iii) C₆H₅COOH → C₆H₅NH₂
(iv) Aniline → 2, 4, 6 tribromoaniline
(v) Benzylchloride → 2-phenyl ethanamine
Answer.

Question. Given reasons : (i) Acetylation of aniline reduces its activation effect.
(ii) CH₃NH₂ is more basic than C₆H₅NH₂
(iii) Although –NH₂ group is o/p directing , yet aniline on nitration gives a significant amount of m-nitroaniline
Answer. (i) Due to the resonance, the electron pair of nitrogen atom gets delocalised towards carbonyl group/resonating structures.
(ii) Because of +I effect in methylamine electron density at nitrogen increases whereas in aniline resonance takes place and electron density on nitrogen decreases / resonating structures.
(iii) Due to protonation of aniline / formation of anilinium ion

More Questions

1.Arrange the following in order of decreasing basic strength

(a) Ethyl amine, Ammonia, Triethyl amine

(b) Aniline, p- Nitroaniline , p- Toluidine

2.Amine group in aniline is ortho and para directing. Why does then aniline on nitration give substantial amount of m-nitroaniline

3.Primary amines have higher boiling points than tertiary amines. Why?

4.‘Amide are more acidic than amines’. Why?

5.Arrange the following amines in the ascending order of basic strength giving reason-EtNH₂, Et₂NH,Et₃N, in aqueous solution?

6.Explain the role of mineral acid in the reaction of a carbonyl compound with KCN (aq)?

7.Why is acetonitrile preferred as a solvent for running organic reaction?

8.Why aniline is acetylated first to prepare mono bromo derivative?

9.Ammonolysis of alkyl halide does not give a corresponding amine in pure state. Explain?

10.Explain why methyl bromide reacts with KCN go give mostly methyl cyanide but it reacts with AgCN to give mostly methyl isocyanide.

11.Why is necessary to maintain the temperature between 273 K and 278 K during diazotization?

12.Why does silver chloride dissolve in aqueous methyl amine solution?

13.How can the following conversion be carried out :-

(a) p-toluidine to 2- bromo-4- methylanline

(b) Aniline to iodobenzene

(c) Aniline to benzonitrile