English
Karnataka Board PUCPUC Science 2nd PUC Class 12

Arrange the following: In decreasing order of the pKb values: C2H5NH2, C6H5NHCH3, (C2H5)2NH and C6H5NH2 - Chemistry

Advertisements
Advertisements

Question

Arrange the following:

 In decreasing order of the pKb values:

C2H5NH2, C6H5NHCH3, (C2H5)2NH and C6H5NH2

Very Long Answer

Solution

In C2H5NH2, only one −C2H5 group is present while in (C2H5)2NH, two −C2H5 groups are present. Thus, the +I effect is more in (C2H5)2NH than in C2H5NH2. Therefore, the electron density over the N-atom is more in (C2H5)2NH than in C2H5NH2. Hence, (C2H5)2NH is more basic than C2H5NH2.

Also, both C6H5NHCH3 and C6H5NHare less basic than (C2H5)2NH and C2H5NH2 due to the delocalization of the lone pair in the former two. Further, among C6H5NHCH3 and C6H5NH2, the former will be more basic due to the +I effect of −CH3 group. Hence, the order of increasing basicity of the given compounds is as follows:

C6H5NH2 < C6H5NHCH3 < C2H5NH2 < (C2H5)2NH

We know that the higher the basic strength, the lower the pKb values.

C6H5NH2 > C6H5NHCH3 > C2H5NH2 > (C2H5)2NH

shaalaa.com
  Is there an error in this question or solution?
Chapter 13: Amines - Exercises [Page 400]

APPEARS IN

NCERT Chemistry [English] Class 12
Chapter 13 Amines
Exercises | Q 4.1 | Page 400
Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×