Question

Rank the following compounds in order of reactivity toward nitration with HNO3:_______. thiophene, benzene, 3-methylthiophene, and 2-methylfuran.

Answer 1

Answer:

3-methylthiophene > thiophene > benzene > 2-methylfuran

Explanation:

Primarily, five membered heterocyclic aromatic rings undergo nitration at carbon-2. This is because, nitration at carbon-2 leads to the formation of three resonance structures while attack at carbon-3 yields only two resonance structures, hence it is less stabilized.

The presence of a methyl group which donates electrons promotes the stabilization of the cation formed in the nitration of 3-methylthiophene.

2-methylfuran is the least reactive towards nitration because the 2-position has been blocked by a methyl group.