Optical activity - 3 | Stereoisomers

Molecule A has an [α]D = - 88°.

Draw the structure of B, which has an [α]D = + 88°.

Calculate the [α]D of a 70/30 mixture of A and B.

Draw the structure of C, which is a constitutional isomer of A and has an [α]D = 0°.
 

Other answers are also possible for C.

[α]D of a 70/30 mixture of A and B: (-88) x (0.7) + (+88) x (0.3) = -35.2°.