NCERT Class XII Chemistry
Chapter - Amines
Questions with Solutions
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Question : 4
Total: 22
Arrange the following :
(i) In decreasing order of thep K b
C 2 H 5 N H 2 , C 6 H 5 N H C H 3 , ( C 2 H 5 ) 2 N H C 6 H 5 N H 2
(ii) In increasing order of basic strength:
C 6 H 5 N H 2 , C 6 H 5 N ( C H 3 ) 2 , ( C 2 H 5 ) 2 N H C H 3 N H 2
(iii) In increasing order of basic strength:
(a) Aniline, p-nitroaniline and p-toluidine
(b)C 6 H 5 N H 2 , C 6 H 5 N H C H 3 C 6 H 5 C H 2 N H 2
(iv) In decreasing order of basic strength in gas phase:
C 2 H 5 N H 2 , ( C 2 H 5 ) 2 N H , ( C 2 H 5 ) 3 N N H 3
(v) In increasing order of boiling point :
C 2 H 5 O H , ( C H 3 ) 2 N H , C 2 H 5 N H 2
(vi) In increasing order of solubility in water :
C 6 H 5 N H 2 , ( C 2 H 5 ) 2 N H , C 2 H 5 N H 2.
(i) In decreasing order of the
(ii) In increasing order of basic strength:
(iii) In increasing order of basic strength:
(a) Aniline, p-nitroaniline and p-toluidine
(b)
(iv) In decreasing order of basic strength in gas phase:
(v) In increasing order of boiling point :
(vi) In increasing order of solubility in water :
Solution:
(i) The order of p K b
C 6 H 5 N H 2 > C 6 H 5 N H C H 3 > C 2 H 5 N H 2 > ( C 2 H 5 ) 2 N H
(iii) p-Nitroaniline < Aniline < p-Toluidine
– N O 2 – C H 3
– N H 2
(iv) In gas phase, basicity follows the order :
( C 2 H 5 ) 3 N > ( C 2 H 5 ) 2 N H > C 2 H 5 N H 2 > N H 3
(ii) C 6 H 5 N H 2 < C 6 H 5 N ( C H 3 ) 2 < C H 3 N H 2 < ( C 2 H 5 ) 2 N H
(iii) p-Nitroaniline < Aniline < p-Toluidine
The availability of l.p. on N of p-nitroaniline is drastically reduced by presence of electron withdrawing
(b) C 6 H 5 N H 2 < C 6 H 5 N H C H 3 < C 6 H 5 C H 2 N H 2
Involvement of l.p. of N in resonance causes aniline to have low basicity. In II, the –Me group through its +I effect improves the electron density on N and therefore its basic strength increases. In III, the (iv) In gas phase, basicity follows the order :
(v) ( C H 3 ) 2 N H < C 2 H 5 N H 2 < C 2 H 5 O H
(vi)C 6 H 5 N H 2 < ( C 2 H 5 ) 2 N H < C 2 H 5 N H 2
Amines can form hydrogen bonds with water and are therefore soluble init. However, the solubility decreases if the mass of the hydrocarbon partincreases.
(vi)
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