JEE MainChemistryAlcohols Phenols and Ethers
Consider the following three diols: (I) Butane-1,4-diol (II) 2,3-Dimethylbutane-2,3-diol (III) Butane-1,3-diol When each of these diols is heated separately with concentrated H₂SO₄ , the major organic products formed are respectively:
Options
- A(I) Tetrahydrofuran, (II) 3,3-Dimethylbutan-2-one, (III) 1,3-Butadiene
- B(I) 1,3-Butadiene, (II) 3,3-Dimethylbutan-2-one, (III) Tetrahydrofuran
- C(I) 1,3-Butadiene, (II) 2,3-Dimethyl-1,3-butadiene, (III) 1,3-Butadiene
- D(I) Tetrahydrofuran, (II) 2,2,3,3-Tetramethyloxirane, (III) 1,3-Butadiene
Correct answer
A. (I) Tetrahydrofuran, (II) 3,3-Dimethylbutan-2-one, (III) 1,3-Butadiene
Step-by-step solution
The reaction of diols with concentrated H₂SO₄ and heat depends on the relative positions of the hydroxyl groups: (I) Butane-1,4-diol: Protonation of one hydroxyl group followed by the loss of water and intramolecular attack by the other hydroxyl group leads to the formation of a stable five-membered cyclic ether. The major product is tetrahydrofuran. (II) 2,3-Dimethylbutane-2,3-diol: This is a vicinal (1,2) diol. Under acidic conditions, it undergoes the pinacol-pinacolone rearrangement. Protonation and loss of wat