(R)-2-Bromooctane is stirred with NaN3 in DMF (clean SN2), and the product is reduced with LiAlH4, which does not touch the stereocentre. The final product is

JEE Advanced levelSingle correct optionDifficulty 3 of 3o3110

$(R)$ -2-Bromooctane is stirred with $NaN X_{3}$ in DMF (clean SN2), and the product is reduced with $LiAlH X_{4}$ , which does not touch the stereocentre. The final product is

Azide displaces bromide with inversion in the polar aprotic solvent. The priorities

Br > C X_{6} H X_{13} > CH X_{3} > H

become

N X_{3} > C X_{6} H X_{13} > CH X_{3} > H

, the same order, so

R

becomes

S

(S)

-2-azidooctane.

LiAlH X_{4}

reduces

- N X_{3}

- NH X_{2}

without any change at carbon, and the priorities

NH X_{2} > C X_{6} H X_{13} > CH X_{3} > H

keep the label

S