At one stereocentre of a Fischer projection, the top group is held fixed and the other three groups are cyclically permuted (left to right to bottom to left). The result is:

Athe enantiomeric configuration
Ba constitutional isomer
Cthe same configuration
Dan epimer only if another centre is also present

Answer: C

A cyclic permutation of three groups with the fourth fixed is equal to two successive interchanges of pairs of groups. Each interchange inverts the configuration, so two cancel. The configuration is therefore unchanged.

Practice Stereoisomerism More on Fischer, Newman and sawhorse projections

Previous questionNext question

More questions on Fischer, Newman and sawhorse projections

In the Fischer projection of glyceraldehyde, CHO is at the top, CH2OH at the bottom, and on the middle carbon OH is on the right and H on th... NEET level
L-Alanine is written as a Fischer projection with COOH at the top, CH3 at the bottom, and on the central carbon NH2 on the left and H on the... NEET level
A Fischer projection of lactic acid has CH3 at the top, COOH at the bottom, and on the central carbon H on the left and OH on the right. Wha... JEE Main level
A sawhorse projection of 2-bromobutane looks along the C2-C3 bond. The front carbon is C2: its three bonds point up (12 o'clock) to CH3, low... JEE Main level
Assertion (A): the anti-staggered conformation of meso-2,3-dibromobutane is achiral. Reason (R): in the anti-staggered conformation the mole... JEE Main level
Looking along the C2-C3 bond of 3-chlorobutan-2-ol, the back carbon is C3 and its groups are Cl at 6 o'clock, CH3 at 2 o'clock and H at 10 o... JEE Main level