JEE Main levelSingle correct optionDifficulty 2 of 3g3177
Naphthalene-1-sulfonic acid is heated with concentrated HX2SOX4 at 160∘C for a long time (only monosulfonated species need be considered). The major product at equilibrium is
Aa 1 : 1 mixture of the 1- and 2-sulfonic acids
Bnaphthalen-1-ol
Cnaphthalene-2-sulfonic acid
Dunchanged naphthalene-1-sulfonic acid
Answer: C
Sulfonation is reversible, so at 160∘C the 1-acid desulfonates and re-sulfonates until the more stable isomer predominates. The 2-acid is the more stable isomer, so it is the major product.