A Fischer projection of 2,3-dihydroxybutanoic acid has the vertical chain, top to bottom: COOH, C2, C3, CH3. C2: left OH, right H. C3: left H, right OH. The configuration is

JEE Main levelSingle correct optionDifficulty 2 of 3st032

A Fischer projection of 2,3-dihydroxybutanoic acid has the vertical chain, top to bottom: $COOH$ , C2, C3, $CH X_{3}$ . C2: left $OH$ , right $H$ . C3: left $H$ , right $OH$ . The configuration is

C2:

OH > COOH > C3 > H

(C3 is

(O, C, H)

, lower than

COOH

with

(O, O, O)

OH

(left)

\to

COOH

(top)

\to

C3 (bottom) is clockwise;

H

is horizontal, so reverse:

S

. C3:

OH > C2 > CH X_{3} > H

OH

(right)

\to

C2 (top)

\to

CH X_{3}

(bottom) is anticlockwise; reverse:

R

. Result

(2 S, 3 R)