The number of optically active steroisomers possible for $\mathrm{CH}_{3}-\mathrm{CH}(\mathrm{OH})-\mathrm{CH}(\mathrm{OH})-\mathrm{CH}(\mathrm{OH})-\mathrm{CH}_{3}$ is
(a)two
(b)four
(c)six
(d)eight
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
Pentane-2,3,4-triol has three stereocentres but the ends are identical: four stereoisomers in all — two meso forms and one pair of enantiomers. Only the enantiomeric pair (2) is optically active.