Isomerism · Question 13

The total number of structural isomers possible for the substituted benzene derivatives with the molecular formula C9H12 is .

Answer

8

Solution

C9H12 = C6H6 ring + 3 more C atoms (all saturated, DBE = 4 is used up by the benzene ring).

(i) One substituent (-C3H7): 2 isomers

[figure]

(ii) Two substituents (-C2H5 and -CH3): 3 isomers

[figure]

(iii) Three -CH3 groups: 3 isomers

[figure]

total structural isomers = 2 + 3 + 3 = 8

Answer: 8