See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Concept: Axial chirality (atropisomerism) vs. point chirality (chiral centre). Step 1 - Identify the structure. BINAP-ol (1,1'-bi-2-naphthol, BINOL) consists of two naphthalene rings joined by a single C–C bond at the 1,1'-positions, each bearing an OH at the 2-position. There is restricted rotation around this biaryl bond due to steric hindrance from the peri-hydrogens, giving rise to stable atropisomers. Step 2 - Check for classical chiral centres. No carbon in BINOL bears four different substituents in the tetrahedral sense; all ring carbons are sp2. Therefore, BINOL has NO conventional (point) chiral centre. Step 3 - Check for axial chirality. The restricted rotation around the 1,1'-biaryl bond creates two non-superimposable mirror-image conformations (atropisomers: Ra and Sa, or (R)- and (S)-BINOL). This is a case of axial chirality. Each enantiomer is optically active and can be isolated as a stable, separable stereoisomer. Step 4 - Evaluate the given structure. The drawing shows a specific configuration (one enantiomer) of BINOL. Because it is a single enantiomer, it is optically active. Step 5 - Eliminate wrong options. (a) Incorrect: BINOL is optically active, but it does NOT possess a chiral centre (no sp3 stereogenic carbon). (b) Incorrect: A pure enantiomer of BINOL is optically active, not inactive. (c) Incorrect: A meso compound requires internal symmetry that cancels chirality; BINOL as drawn is a single chiral atropisomer, not meso. (d) Correct: BINOL is optically active due to axial chirality (restricted biaryl rotation / atropisomerism) but contains no classical chiral centre. Therefore, the correct answer is D.