Question

Question #c6802

Answer 1

option(B) yields an optically active product upon reduction of `"NaBH"_4`

Explanation:

Chiral molecules have no line of symmetry and this makes them optically active.When you look at the molecules before the reaction they all are asymmetric and they are optically active.

A) D-ribose

I didn't get an image with only D-ribose
There is a line of symmetry in this aditol, therefore it is achiral and not optically active

(B) L-lyxose

The product is chiral and optically active

(C)L-xylose

There is a line of symmetry and this aditol is achiral

(D)D-xylose

There is a line of symmetry and this aditol is achiral

In the last 2 options I have used the same image because the configuration of aldehyde group is not the same in both the aldopentose.