Important Questions for Class 12 Chemistry Chapter 13 Amines: Organic Compounds Containing Nitrogen Class 12 Important Questions

Important Questions for Class 12 Chemistry Chapter 13Amines: Organic Compounds Containing Nitrogen Class 12 Important Questions

Amines: Organic Compounds Containing Nitrogen Class 12 Important Questions Very Short Answer Type

Question 1.
Why is an alkylamine more basic than ammonia? (Delhi 2009)
Answer:
Due to electron releasing inductive effect (+1) of alkyl group, the electron density on the nitrogen atom increases and thus, it can donate the lone pair of electrons more easily than ammonia.

Question 2.
Arrange the following compounds in an increasing order of basic strengths in their aqueous solutions : NH₃, CH₃NH₂, (CH₃)₂NH, (CH₃)₃N (All India 2009)
Answer:
Basicity order (due to stability of ammonium cation)
(CH₃)₂ NH > CH₃NH₂ > (CH₃)₃ N > NH₃

Question 3.
Give the IUPAC name of H2N — CH2—CH2—CH = CH2. (Delhi 2010)
Answer:
IUPAC name : But-3-ene-1-amine

Question 4.
Arrange the following compounds in an increasing order of their solubility in water : C6H5NH2, (C2H5)2NH, C2HSNH2 (Delhi & All India 2011)
Answer:
C₆H₅NH₂ < (C₂H₅)₂NH < C2₂H₅NH₂

Question 5.
Give a chemical test to distinguish between ethylamine and aniline. (All India 2011)
Answer:
Ethylamine and aniline :
By Azo dye test: It involves the reaction of any aromatic primary amine with HNO₂(NaNO₂ + dil. HCl) at 273-278 K followed by treatment with an alkaline solution of 2-naphthol when a brilliant yellow, orange or red coloured dye is obtained.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 1

Question 6.
Arrange the following in the decreasing order of their basic strength in aqueous solutions: CH₃NH₂, (CH₃)₂ NH, (CH₃)₃N and NH₃ (Delhi 2012)
Answer:
(CH₃)₂ NH > CH₃NH₂ > (CH₃)₃ N > NH₃

Question 7.
Arrange the following in increasing order of their basic strength in aqueous solution: CH₃.NH₂, (CH₃)₃N, (CH₃)₂NH (Delhi 2013)
Answer:
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 2

Question 8.
Write the structure of 2-aminotoluene. (All India 2013)
Answer:
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 3

Question 9.
Write the structure of n-methylethanamine. (All India 2013)
Answer:
Structure of n-methylethanamine :
H₃C—H₂C—NH—CH₂

Question 10.
Write the structure of prop-2-en-l-amine. (All India 2013)
Answer:
H₂C=CH—H₂C—NH₂

Question 11.
How may methyl bromide be preferentially converted to methyl isocyanide? (Comptt. Delhi 2013)
Answer:
Bit carbylamine reaction:
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 4

Question 12.
Arrange the following compounds in increasing order of solubility in water :
C₆H₅NH₂, (C₂H₅)₂NH, C₂H₅NH₂ (Delhi 2014)
Answer:
C₆H₅NH₂ < (C₂H₅)₂NH < C₂H₅NH,

Question 13.
Arrange the following in increasing order of basic strength :
C₆H₅NH₂, C₆H₅NHCH₃, C₆H₅CH₂NH₂ (Delhi 2014)
Answer:
C₆H₅NH₂ < C₆H₅NHCH₃ < C₆H₅CH₂NH₂

Question 14.
Arrange the following in increasing order of basic strength :
C₆H₅NH₂, C₆H₅NHCH₃, C₆H₅N(CH₃)₂ (Delhi 2014)
Answer:
C₆H₅N(CH₃)₂ > C₆H₅NHCH₃ > C₆H₅NH₂

Question 15.
The conversion of primary aromatic amines into diazonium salts is known as (All India 2014)
Answer:
Diazotization.

Question 16.
Out of CH₃—NH₂ and (CH₃)₃N, which one has higher boiling point? (Comptt. Delhi 2014)
Answer:
CH₃—NH₂ has higher boiling point than (CH₃)₃N.

Question 17.
Complete the following reaction equation : (Comptt. Delhi 2015)
Answer:
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 5

Question 18.
Arrange the following in increasing order of basic strength (Comptt. All India 2015)
Aniline, p-Nitroaniline and p-Toluidine
Answer:
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 6

Question 19.
Write the IUPAC name of the given compound: (Delhi 2016)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 7
Answer:
2, 4, 6-Tribromoaniline

Question 20.
Write IUPAC name of the following compound: (CH₃CH₂)₂NCH₃ (Delhi 2017)
Answer:
N-Ethyl-N-methylethanamine

Question 21.
Write the IUPAC name of the following compound: (Comptt. All India 2017)
CH₃NHCH(CH₃)₂
Answer:
IUPAC name: N-Methylpropan-2-amine

Question 22.
Write the IUPAC name of the following compound: (Delhi 2017)
(CH₃)₂N-CH₂CH₃
Answer:
IUPAC name: N, N Dimethylamine

Question 23.
Write IUPAC name of the following compound : (Comptt. All India 2017)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 8
Answer:
IUPAC name : N, N-Dimethylbutanamine.

Amines: Organic Compounds Containing Nitrogen Class 12 Important Questions Short Answer Type -I [SA – I]

Question 24.
Give the chemical tests to distinguish between the following pairs of compounds :
(i) Ethyl amine and Aniline
(ii) Aniline and Benzylamine (All India 2010)
Answer:
(i) Ethylamine and aniline :
By Azo dye test: It involves the reaction of any aromatic primary amine with HNO₂(NaNO₂ + dil. HCl) at 273-278 K followed by treatment with an alkaline solution of 2-naphthol when a brilliant yellow, orange or red coloured dye is obtained.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 1

(ii) Distinction between Aniline and Benzylamine :
By Nitrous acid test : Benzylamine reacts with HNO₂ to form a diazonium salt which being unstable even at low temperature, decomposes with evolution of N₂ gas
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 9

Question 25.
Identify A and B in each of the following processes : (All India 20100
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 10
Answer:

Question 26.
Give the chemical tests to distinguish between the following pairs of compounds :
(i) Methylamine and Dimethylamine
(ii) Aniline and N-methylaniline (All India 2010)
Answer:
(i) Methylamine and Dimethylamine :
By Carbylamine test: Methylamine being a primary amine gives this test but Dimethylamine being a secondary amine does not.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 12

(ii) Aniline and N-methylaniline
By Carbylamine test : Aniline is a 1° aromatic amine while N-methylaniline is a secondary aromatic amine. Therefore only 1° aromatic amine gives this test.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 13

Question 27.
Describe the following giving the relevant chemical equation in each case :
(i) Carbylamine reaction
(ii) Hofmann’s bromamide reaction (All India 2012)
Answer:
(i) Carbylamine reaction : Aliphatic and aromatic primary amines on heating with chloroform and ethanolic KOH form isocyanides or carbylamines which are foul smelling substances. This reaction is known as carbylamines reaction.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 14

(ii) Hofmann’s bromamide reaction : Primary amines can be prepared by treating an amide with Br₂ in an aqueous or alcoholic soln of NaOH.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 15

Question 28.
Complete the following reaction equations : (All India 2012)
(i) C₆H₅N₂Cl + H₃PO₂ + H₂O →
(ii) C₆H₅NH₂ + Br₂ (aq) →
Answer:
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 16

Question 29.
Give IUPAC names of the following compounds : (Comptt. Delhi 2012)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 17
Answer:
(a) IUPAC name : Methyl prop-2-en-1-amine
(b) IUPAC name : Phenyl acetamide

Question 30.
How are the following conversions carried out :
(a) Aniline to p-hydroxyazobenzene
(b) Ethanoyl chloride to Ethanenitrile. (Comptt. Delhi 2012)
Answer:
(a) Aniline to p-hydroxyazobenzene
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 18

Question 31.
How are the following conversions carried out?
(i) CH₃CH₂Cl to CH₃CH₂CH₂NH₂
(ii) Benzene to aniline (Comptt. Delhi 2012)
Answer:
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 19

Question 32.
How would you account for the following :
(a) Aniline is a weaker base than cyclohexyl amine.
(b) Methylamine in aqueous medium gives reddish-brown precipitate with FeCl₃. (Comptt. All India 2012)
Answer:
(a) In aniline, the lone pair of electrons on the N-atom is delocalised over the benzene ring. As a result, the electron density on the nitrogen decreases.
But in cyclohexylamine, the lone pair of electrons on N-atom is readily available due to absence of reelections. Hence aniline is weaker base than cyclohexylamine.
(b) Methylamine being more basic than H₂O, it accepts a proton from water liberating OH^– ions.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 20

Question 33.
How would you account for the following :
(a) Electrophilic susbstitution in case of aromatic amines takes place more readily than benzene.
(b) Ethanamide is a weaker base than ethanamine. (Comptt. All India 2012)
Answer:
(a) Aniline exists as a resonance hybrid of the following five structures :
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 21
The electron density is maximum at ortho and para positions to the – NH₂ group. But in benzene there is no delocalisation of electron at any position and hence electrophilic substitution in case of aromatic amines takes place more readily than benzene.

(b) In ethanamide the lone pair of electron of N-atom is not available due to resonance structure
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 22
So it is a weaker base.

Question 34.
Illustrate the following reactions :
(a) Sandmeyer’s reaction
(b) Coupling reaction (Comptt. All India 2012)
Answer:
(a) Sandmeyer’s reaction : Aniline reacts with NaNO₂ in HCl at 273 – 278 K giving diazonium salt which further reacts with cuprous chloride/bromide to give chloro or bromo benzene.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 23
This reaction is Sandmeyer’s reaction.
(b) Coupling reaction : Arene diazonium salts react with highly reactive aromatic compounds such as phenols and amines to form brightly coloured azo compounds.
Ar – N = N – Ar. This reaction is known as coupling reaction.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 24

Question 35.
Give chemical tests to distinguish between the following pairs of compounds :
(a) Aniline and Ethylamine
(b) Ethylamine and Dimethylamine (Comptt. Delhi 2013)
Answer:
(a) Ethylamine and aniline :
By Azo dye test: It involves the reaction of any aromatic primary amine with HNO₂(NaNO₂ + dil. HCl) at 273-278 K followed by treatment with an alkaline solution of 2-naphthol when a brilliant yellow, orange or red coloured dye is obtained.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 1

(b) Ethylamine and dimethylamine can be distinguished by the carbylamine test.
Carbylamine test: Aliphatic and aromatic amines on heating with chloroform and ethanolic potassium hydroxide form foul smelling isocyanides or carbylamines. Ethylamine (being an aliphatic primary amine) gives a positive carbylamine test, but dimethylamine does not.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 25

Question 36.
Explain the following reactions :
(a) Gabriel Phthalimide reaction
(b) Coupling reaction (Comptt. Delhi, Comptt. All India 2013)
Answer:
(a) Gabriel phthalimide synthesis : It is used to prepare 1° amine (Primary amine). The starting compound is a phthalimide. But aromatic primary amines cannot be prepared by this method because aryl halides do not undergo nucleophilic substitution with the anion formed by phthalimide.
Example :
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 26

(b) Coupling reaction : Arene diazonium salts react with highly reactive aromatic compounds such as phenols and amines to form brightly coloured azo compounds.
Ar – N = N – Ar. This reaction is known as coupling reaction.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 24

Question 37.
Give reasons :
(a) Aniline is a weaker base than cyclohexyl amine.
(b) It is difficult to prepare pure amines by ammonolysis of alkyl halides. (Comptt. All India 2013)
Answer:
(a) In aniline, the lone pair of electrons on the N-atom is delocalised over the benzene ring. As a result, the
electron density on the nitrogen decreases.
But in cyclohexylamine, the lone pair of electrons on N-atom is readily available due to absence of π-electrons. Hence aniline is weaker base than cyclohexylamine.
(b) Because the primary amine formed by ammonolysis itself acts as a nucleophile and produces further 2° and 3° alkyl amine.

Question 38.
Give reasons :
(i) Electrophilic substitution in aromatic amines takes place more readily than benzene.
(ii) CH₃CONH₂ is weaker base than CH₃CH₂NH₂. (Comptt. All India 2013)
Answer:
(i) Due to the strong activating effect of the NH₂ group, aromatic amines undergo electrophilic substitution reactions readily than benzene.
(ii) In case of acetamide due to resonance, the lone pair of electrons on the nitrogen atom is delocalized over keto group which decreases electron density hence less basic while in ethylamine due to +1 effect of ethyl group electron density increases on N-atom and hence basic character increases.

Question 39.
(i) Arrange the following compounds in an increasing order of basic strength :
C₆H₅NH₂, C₆H₅N(CH₃)₂, (C₂H₅)₂NH and CH₃NH₂
(ii) Arrange the following compounds in a decreasing order of pKb values :
C₂H₅NH₂, C₆H₅NHCH₃, (C₂H₅)₂NH and C₆H₅NH (Comptt. Delhi 2014)
Answer:
(i) Increasing order of basic strength
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 27
(ii) Decreasing order of pKb values
C₆H₅NH₂ < C₆H₅NHCH₃ < C₂H₅NH₂ < (C₂H₅)₂NH

Question 40.
Give a chemical test to distinguish between each of the following pairs of compounds :
(i) Ethylamine and Aniline
(ii) Aniline and Benzylamine (Comptt. All India 2014)
Answer:
(i) Ethylamine and aniline :
By Azo dye test: It involves the reaction of any aromatic primary amine with HNO₂(NaNO₂ + dil. HCl) at 273-278 K followed by treatment with an alkaline solution of 2-naphthol when a brilliant yellow, orange or red coloured dye is obtained.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 1

Question 41.
Write the chemical equations involved in the following reactions: (All India 2016)
(i) Hoffmann-bromamide degradation reaction
(ii) Carbylamine reaction
Answer:
(i) Hoffmann’s bromamide reaction : In this reaction, migration of an alkyl or aryl group takes place from carbonyl carbon of the amide to the nitrogen atom. Therefore the amine so formed has one carbon atom less than that of amide.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 28

(ii) Carbylamine reaction. This reaction is used to distinguish primary amines from 2° and 3° amines as it is only given by 1° amines with the production of a very bad smelling organic compound.
For example :
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 29

Amines: Organic Compounds Containing Nitrogen Class 12 Important Questions Short Answer Type -II [SA – II]

Question 42.
Giving an example for each describe the following reactions :
(i) Hofmann’s bromamide reaction
(ii) Gatterman reaction
(iii) A coupling reaction (Delhi 2009)
Answer:
(i) Hofmann’s bromamide reaction : When amide is treated with bromide in alkaline solution, an amide yields an amine containing one carbon less than the starting amide.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 30

(ii) Gatterman reaction: When benzene or its derivative is treated with carbon monoxide and hydrogen chloride in the presence of anhydrous aluminium chloride or cuprous chloride, it gives benzaldehyde or substituted benzaldehyde.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 31
Gattermann Koch reaction : Diazonium salt reacts with hydrogen halide in presence of copper powder giving haloarene.

(iii) A coupling reaction : Arene diazonium salts react with highly reactive aromatic compounds such as phenols and amines to form brightly coloured azo compounds.
Ar – N = N – Ar. This reaction is known as coupling reaction.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 33

Question 43.
Complete the following reaction equations: (All India 2009)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 34
Answer:
Reduction reaction

Question 44.
Complete the following reaction equations :
(i) C₆H₅Cl + CH₃COCl →
(ii) C₂H₅NH₂ + C₆H₅SO₂Cl →
(iii) C₂H₅NH₂ + HNO₂ →
Answer:
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 36

Question 45.
In the following cases rearrange the compounds as directed : (Delhi 2010)
(i) In an increasing order of basic strength :
C₆H₅NH₂, C₆H₅ N(CH₃)₂, (C₂H₅)₂NH and CH₃NH₂
(ii) In a decreasing order of basic strength :
Aniline, p-nitroaniline and p-toluidine
(iii) In an increasing order of pK_b values :
C₂H₅NH₂, C₆H₅ NHCH₃, (C₂H₅)₂NH and C₆H₅NH₂
Answer:
(i) Order of basic strength :
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 37
Since a stronger base has a lower pKb value therefore basic strength order.
(C₂H₅)₂NH > C₂H₅NH₂ > C₆H₅NHCH₃ > C₆H₅NH₂

Question 46.
Complete the following chemical equations : (Delhi)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 38
Answer:

Question 47.
(a) Explain why an alkylamine is more basic than ammonia?
(b) How would you convert
(i) Aniline to nitrobenzene (ii) Aniline to iodobenzene (Delhi 2011)
Answer:
(a) Due to electron releasing inductive effect (+1) of alkyl group, the electron density on the nitrogen atom increases and thus, it can donate the lone pair of electrons more easily than ammonia.

(b) (i) Aniline to nitrobenzene
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 40

Question 48.
Complete the following chemical equations: (Delhi 2011)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 41
Answer:

Question 49.
State reasons for the following :
(i) pK_b value for aniline is more than that for methylamine.
(ii) Ethylamine is soluble in water whereas aniline is not soluble in water.
(iii) Primary amines have higher boiling points than tertiary amines. (All India 2011)
Answer:
(i) Higher the pK_b value, lower will be the basicity therefore aniline is less basic than methylamine because the
lone pair of electrons on nitrogen atom gets delocalized over the benzene ring are unavailable for protonation due to resonance in aniline which is absent in case of alkylamine.
(ii) Ethylamine is soluble in water due to its capability to form H-bonds with water while aniline is insoluble in water due to larger hydrocarbon part which tends to retard the formation of H-bonds.
(iii) Due to presence of two H-atoms on N-atom of primary amines, they undergo extensive intermolecular H-bonding while tertiary amines due to the absence of a H-atom on the N-atom, do not undergo H- bonding. As a result, primary amines have higher boiling points than 3° amines.

Question 50.
Write chemical equations for the following conversions :
(i) Nitrobenzene to benzoic acid.
(ii) Benzyl chloride to 2-phenylethanamine
(iii) Aniline to benzyl alcohol. (Delhi 2012)
Answer:
(i) Nirtobenzene to benzoic acid :
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 43
(ii) Benzyl chloride to 2-phenylethanamine

(iii) Aniline to benzyl alcohol

Question 51.
Give the structure of A, B and C in the following reactions: (Delhi 2013)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 46
Answer:

Question 52.
Give the structure of A, B and C in the following reactions : (Delhi 2013)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 49
Answer:

Question 53.
Complete the following reactions : (All India 2013)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 51
Answer:

Question 54.
Write the main products of following reactions: (All India 2013)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 53
Answer:

Question 55.
Give the structures of A, B and C in the following reactions : (Delhi 2014)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 56
Answer:

Question 56.
How will you convert the following :
(i) Nitrobenzene into aniline
(ii) Ethanoic acid into methanamine
(iii) Aniline into N-phenylethanamide
(Write the chemical equations involved) (Delhi 2014)
Answer:
(i) Nitrobenzene into aniline
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 58

Question 57.
Account for the following :
(i) Primary amines (R-NH₂) have higher boiling point than tertiary amines (R₃N).
(ii) Aniline does not undergo Friedel – Crafts reaction.
(iii) (CH₃)₂NH is more basic than (CH₃)₃N in an aqueous solution. (All India 2014)
Answer:
(i) Due to presence of two H-atoms on N-atom of primary amines, they undergo extensive intermolecular H-bonding while tertiary amines due to the absence of a H-atom on the N-atom, do not undergo H- bonding. As a result, primary amines have higher boiling points than 3° amines.
(ii) Aniline being a Lewis base reacts with Lewis acid AlCl₃ to form a salt.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 60
As a result, N of aniline acquires positive charge and hence it acts as a strong deactivating group for electrophilic substitution reaction. Consequently, aniline does not undergo Freidel Craft reaction.
(iii) Due to more steric hindrance in (CH₃)₃N it is less basic than (CH₃)₂NH.

Question 58.
Account for the following:
(i) Aniline does not give Friedel-Crafts reaction.
(ii) Ethylamine is soluble in water whereas aniline is not.
(iii) pK_b of methylamine is less than that of aniline. (Comptt. Delhi 2014)
Answer:
(i) Aniline being a Lewis base reacts with Lewis acid AlCl₃ to form a salt.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 61
As a result, N of aniline acquires positive charge and hence it acts as a strong deactivating group for electrophilic substitution reaction. Consequently, aniline does not undergo Freidel Craft reaction.
(ii) Ethylamine is soluble in water due to its capability to form Fl-bonds with water while aniline is insoluble in water due to larger hydrocarbon part which tends to retard the formation of H-bonds.
(iii) In aniline due to resonance lone pair of electron of nitrogen atom is delocalised due to which it is weaker base than methyl amine.
Hence Aniline has high pK_b molecule i.e., methylamine has less pK_b molecule.

Question 59.
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 C₆H₇N. Write the structures and IUPAC names of compounds A, B and C. (Comptt. Delhi 2015)
Answer:
The data shows that C₆H₇N may be C₆H₅NH₂ i.e. Aniline. Since it is obtained by heating with Br₂ and KOH (Hoffmann bromamide reaction), then the compound ‘B’ is Benzamide C₆H₅CONH₂ which is in turn obtained by reaction with aqueous ammonia then the compound ‘A’ can be Benzoic acid i.e. C₆H₅COOH
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 62

Question 60.
Write the structures A, B and C in the following : (Delhi 2016)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 63
Answer:

Question 61.
Give reasons for the following:
(i) Aniline does not undergo Friedal-Crafts reaction.
(ii) (CH₃)₂ NH is more basic than (CH₃)₃ N in an aqueous solution.
(iii) Primary amines have higher boiling point than tertiary amines. (All India 2016)
Answer:
(i) Aniline being a Lewis base reacts with Lewis acid AlCl₃ to form a salt.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 65
As a result, N of aniline acquires positive charge and hence it acts as a strong deactivating group for electrophilic substitution reaction. Consequently, aniline does not undergo Freidel Crafts reaction.
(ii) In (CH₃)N there is maximum steric hindrance and least solvation but in (CH₃)₂NH the solvation is more and the steric hindrance is less than in (CH₃)₃NH; although + I effect is less, since there are two methyl groups; di-methyl amine is still a stronger base than tri-methyl.
(iii) Due to presence of two H-atoms on N-atom of primary amines, they undergo extensive intermolecular H-bonding while tertiary amines due to the absence of a H-atom on the N-atom, do not undergo H- bonding. As a result, primary amines have higher boiling points than 3° amines.

Question 62.
Write major product(s) in the following reactions : (Comptt. Delhi 2016)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 66
Answer:

Question 63.
Describe a method for the identification of primary, secondary and tertiary amines. Also write chemical equations of the reaction involved. (Comptt. Delhi 2016)
Answer:
Benzenesulphonyl chloride (C₆H₅SO₂Cl), which is also known as Hinsberg’s reagent, reacts with primary and secondary amines to form sulphonamides and tertiary amine does not react.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 69
It does not react with tertiary amines.

Question 64.
Write the products A and B in the following : (Comptt. All India 2016)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 70
Answer:

Question 65.
Give reasons:
(i) Acetylation of aniline reduces its activation effect,
(ii) CH₃NH₂ is more basic than C₆H₅NH₂.
(iii) Although —NH₂ is o/p directing group, yet aniline on nitration gives a significant amount of m-nitroaniline. (Delhi 2017)
Answer:
(i) Acetylation of aniline reduces its activation effect because acetyl group being electron withdrawing group attracts the lone pair of electrons of the N-atom towards carboxyl group and the lone pair of electrons on N is less available for donation to benzene ring by resonance.
(ii) CH₃NH₂ is more basic than aniline due to availability of lone pair of electrons for donation while in aniline lone pair of electrons on the nitrogen atom is delocalised over benzene ring and thus unavailable for donation.
(iii) Because of nitration in an acidic medium, aniline gets protonated to give anilinium ion which is indirecting.

Question 66.
Give reasons for the following:
(a) Acetylation of aniline reduces its activation effect.
(b) CH₃NH₂ is more basic than C₆H₅NH₂.
(c) Although —NH₂ is o/p directing group, yet aniline on nitration gives a significant amount of m-nitroaniline. (All India 2017)
Answer:
(i) Acetylation of aniline reduces its activation effect because acetyl group being electron withdrawing group attracts the lone pair of electrons of the N-atom towards carboxyl group and the lone pair of . electrons on N is less available for donation to benzene ring by resonance.
(ii) CH₃NH₂ is more basic than aniline due to availability of lone pair of electrons for donation while in aniline lone pair of electrons on the nitrogen atom is delocalised over benzene ring and thus unavailable for donation.
(iii) Because of nitration in an acidic medium, aniline gets protonated to give anilinium ion which is indirecting.

Question 67.
Write the structures of compounds A, B and C in each of the following reactions: (All India 2017)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 72
Answer:

Question 68.
Illustrate Sandmeyer’s reaction with the help of a suitable example. (Comptt. Delhi 2017)
Answer:
Sandmeyer’s reaction: The substitution of diazo group of benzene diazonium chloride by Chloro, Bromo and Cyano group with the help of solution of CuCl dissolved in HCl, CuBr/HBr and CuCN/KCN respectively is known as Sandmeyer’s reaction.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 74

Question 69.
Identify A, B and C in the following reactions : (Comptt. Delhi 2017)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 75
Answer:

Question 70.
Identify A, B and C in the following reactions : (Comptt. All India 2017)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 76
Answer:

Amines: Organic Compounds Containing Nitrogen Class 12 Important Questions Long Answer Type [LA]

Question 71.
An aromatic compound JA’ of molecular formula C₇H₂₇ON undergoes a series of reactions as shown below. Write the structures of A, B, C, D and E in the following reactions : (Delhi 2015)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 78
Answer:

Question 72.
(a) Write the structures of main products when aniline reacts with the following reagents :
(i) Br₂ water (ii) HCI (iii) (CH₃CO)₂O/pyridine
(b) Arrange the following in the increasing order of their boiling point :
C₂H₅NH₂, C₂H₅OH, (CH₃)₃N
(c) Give a simple chemical test to distinguish between the following pair of compounds : (CH₃)₂NH and (CH₃)₃N (Delhi 2015)
Answer:
(a) (i) Br₂ water
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 80

(b) Increasing order of boiling point :
(CH₃)₃ < C₂H₅NH₂ < C₂H₂OH

(c) By Hinsberg test, secondary amines or (CH₃)₃NH shows precipitate formation which is insoluble in KOH. Tertiary amines or (CH₃)₃N do not react with Hinsberg’s reagent (benzene sulphonyl chloride).

Question 73.
An aromatic compound ‘A’ of molecular formula C₇H₆O₃ undergoes a series of reactions as shown below. Write the structures of A, B, C, D and E in the following reactions : (All India 2015)
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 81
Answer:

Question 74.
(a) Write the structures of main products when benzene diazonium chloride reacts with the following reagents :
(i) H₃PO₂ + H₂O (ii) CuCN/KCN (iii) H₂O
(b) Arrange the following in the increasing order of their basic character in an aqueous solution :
C₂H₅NH₂, (C₂H₅)₂NH, (C₃H₅)₃N
(c) Give a simple chemical test to distinguish between the following pair of compounds :
C₆H₅—NH₂ and C₆H₅—NH—CH₃ (All India 2015)
Answer:
(a) The structure of main products when aniline (benzene diazonium chloride) reacts with the following reagents :
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 83
(b) C₂H₅NH₂ < (C₃H₅)₃N < (C₂H₅)₂NH
(c) Aniline and Benzylamine can be distinguished by the Nitrous acid test. Benzylamine reacts with HNO₂ to form a diazonium salt which being unstable even at low temperature, decomposes with evolution of N₂ gas.
Important Questions for Class 12 Chemistry Chapter 13 Amines Organic Compounds Containing Nitrogen Class 12 Important Questions 84

Important Questions for Class 12 Chemistry

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Important Questions for Class 12 Chemistry Chapter 13 Amines: Organic Compounds Containing Nitrogen Class 12 Important Questions