Discussion Forum



1)

Hydrogen bonding plays a central role in the following phenomena


A) ice floats phenomena

B) higher Lewis basicity of primary amines than tertiary amines in aqueous solutions

C) formic acid is more acidic than acetic acid

D) dimerisation of acetic acid in benzene

Answer:

Option A,B,D

Explanation:

Plan   This problem can be  solved by using the concept of H-bonding and applications of H-bonding

(a) Ice floats  in water  due to the low density of ice as compared to water which is due to open cage-like structure (formed by intermolecular H-bonding)

(b)  Basic strength of RNH2 >R3 N. It is also explained by hydrogen bonding

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 Two H- bonds are possible  with water present  in aqueous solution. (stabilize by solvation)

2232021562_m7.JPG

 No H bonding is possible with water present in aqueous solution.(stabilization by solvation is very less)

 (c)  

 2232021434_m8.JPG

 More acidic due to the presence of H. (Due to the absence of electron-donating group)

2232021636_m9.JPG

 Less acidic than HCOOH due to presence of CH3-

(Electron donating group)

(d) Dimerisation of acetic acid in benzene  is due to intermolecular hydrogen bonding

2232021572_m10.JPG