badge image

Enroll For Free Now & Improve Your Performance.

User Icon
User Icon
User Icon
User Icon
User Icon

Thank you for registering.

One of our academic counsellors will contact you within 1 working day.

Please check your email for login details.

Use Coupon: CART20 and get 20% off on all online Study Material

Total Price: Rs.

There are no items in this cart.
Continue Shopping
Grade: 12


Does the order of the basicity of methyl-substituted amines and ethyl-substituted amines change in a non-aqueous medium?

one year ago

Answers : (2)

25333 Points

The ammonium cation (protonated form) of aliphatic amine is solvation-stabilised by H2O molecules via Hydrogen-bonding in aqueous solution.

Ammonium cation of primary amine (RNH3+) is maximum solvated of all types (primary, secondary & tertiary) due to greater number of hydrogens directly attached to nitrogen and hence their hydrogen bonding with oxygen of water(solvent) molecules.

In total, three effects are most useful to decide basic character of simple aliphatic amines in aqueous solution. (a) Inductive effect – which favors tertiary amine to be more basic due to greater + I effect of three alkyl groups directly attached to nitrogen (b) Solvation effect- which favor primary amine to be more basic due to greater solvation of its cation. (c) Steric factor – which causes tertiary amine to be less basic due to steric hindrance to approach of proton towards nitrogen.

As a combined result of above three factors, in aq solution, the order of basic character (pKb values in brackets) in isomeric aliphatic amines are different in different cases-

  1. (CH3)2NH [3.27] > CH3NH2 [3.38] > (CH3)3N [4.22] > NH3 [4.75]
  2. (C2H5)2NH [3.0] > (C2H5)3N [3.25] > C2H5NH2 [3.29] > NH3 [4.75]
  3. Me2CH-NH2 > NH3 > (Me2CH)2NH > (Me2CH)3N
  4. NH3 > Me3C-NH2 > (Me3C)2NH > (Me3C)3N
one year ago
Vikas TU
13783 Points
Dear student 
the compounds , NH3, CH3NH2, (CH3)2NH , (CH3)3N
when considered on the basis of inductive effect and steric hindrance can be arranged in the increasing order as follows:
Ammonia shows no steric hindrance and no inductive effect, so:
the increasing order is :
(CH3)2NH > CH3NH2> (CH3)3N> NH3
In (CH3)2NH two alkyl groups increase the e- density. This is decreased in (CH3)3NH. However  due to more steric hindrance in (CH3)3N the order of basicity gets reversed , thus (CH3)2NH >  (CH3)3N
Hope this information will clear your doubts regarding the topic. If you have any other doubts please ask here on the forum and our experts will try to solve them as soon as possible.
one year ago
Think You Can Provide A Better Answer ?
Answer & Earn Cool Goodies

Course Features

  • 731 Video Lectures
  • Revision Notes
  • Previous Year Papers
  • Mind Map
  • Study Planner
  • NCERT Solutions
  • Discussion Forum
  • Test paper with Video Solution

Course Features

  • 70 Video Lectures
  • Revision Notes
  • Test paper with Video Solution
  • Mind Map
  • Study Planner
  • NCERT Solutions
  • Discussion Forum
  • Previous Year Exam Questions

Ask Experts

Have any Question? Ask Experts

Post Question

Answer ‘n’ Earn
Attractive Gift
To Win!!! Click Here for details