MolSynapsequestion bank
MolSynapse / Question bank / Amines and Aromatic Nitrogen Compounds / Basicity of amines
JEE Advanced levelSingle correct optionDifficulty 3 of 3nc031

Which statement correctly compares N,N-dimethylaniline (X) with N,N,2,6-tetramethylaniline (Y)?

  1. AX is the stronger base, since the 2,6-methyl groups are electron-withdrawing
  2. BX and Y are equally basic, since both are tertiary amines
  3. CY is the stronger base, since the 2,6-methyl groups twist the group out of the plane of the ring, reducing delocalisation of the lone pair (steric inhibition of resonance)
  4. DX is the stronger base, since the ortho effect always lowers basicity through resonance in Y

Answer: C

In X the nitrogen lone pair is conjugated with the ring. In Y the two ortho methyl groups clash with the N-methyl groups, forcing the group out of the ring plane, so the lone pair is localised and more available for protonation (steric inhibition of resonance). Hence Y is the stronger base.
Practice Amines and Aromatic Nitrogen Compounds More on Basicity of amines
Previous questionNext question

More questions on Basicity of amines