Question

An organic compound $\left( C _{8} H _{10} O _{2}\right)$ rotates plane-polarized light. It produces pink color with neutral $FeCl _{3}$ solution.What is the total number of all the possible isomers for this compound?

Answer 1

(Considering that all isomers satisfy the given conditions) Since given compound produces pink colour with neutral FeCl3. So, it must have at least one –OH group attached to benzene ring.
Also, given compound is optically active, it means it should have a chiral centre, which is only possible when it has –CH(OH)CH3.
DBE (Double bond equivalent) of C8H10O2 is

= $\text{Number of carbon atoms} - \left(\frac{\text{Number of monovalent atoms}}{2}\right) + 1$

= $8 - \frac{10}{2} + 1 = 4$
So, total isomeric structures = 6