JEE Main · 2023 · 01 Feb 2023 · Shift 1 · General Organic Chemistry

A compound is optically active only if it is non-superimposable on its mirror image. The 4-(phenylmethylene)cyclohexane-1-carboxylic acid carries a different pair of groups at each end of its long axis, phenyl and hydrogen on the exocyclic double bond and carboxyl and hydrogen on the opposite ring carbon, so, like an allene with two unlike ends, it has no plane of symmetry and is chiral. The propan-2-ol bearing two different aryloxy arms has a central carbon joined to hydroxyl, hydrogen and two unlike $\mathrm{C}{\mathrm{H}}_2\mathrm{OAr}$ groups, a genuine stereocentre, so it too is chiral. The tartaric acid shown has both hydroxyls on the same side of the Fischer projection, giving an internal mirror plane and a meso, inactive molecule; the fully hydroxylated cyclohexane drawn is a meso inositol with a plane of symmetry; and the methylenecyclopropanedicarboxylic acid has its two carboxyl groups on the same face, again supplying a mirror plane. The number of chiral compounds is 2.