Q.Identify the compound (A) in the following reaction
(a cyclohexane ring carrying an exocyclic =CH-C6H5 double bond) $\xrightarrow[\text{ii) Zn/H}_2\text{O}]{\text{i) O}_3}$ cyclohexanone + (A)

Step 1. The starting material is a cyclohexane ring with an EXOCYCLIC double bond, ring-C=CH-C6H5 (a benzylidenecyclohexane), reacted with O3 then Zn/H2O -- a standard reductive ozonolysis, cleaving that one C=C bond into two separate carbonyl fragments.

Step 2. The RING carbon of the double bond becomes a ring C=O -- since it is flanked by two ring CH2 groups (no H on that alkene carbon itself, both substituents being ring carbons), this fragment is a ketone: cyclohexanone (already given as the other, main product in the question).

Step 3. The EXOCYCLIC carbon of the double bond, =CH-C6H5, carries one phenyl group and one H, so on cleavage it becomes an aldehyde: C6H5-CHO, benzaldehyde -- this is compound (A). …

Identify the two substituents on EACH alkene carbon separately, then decide each fragment's carbonyl type: two carbon substituents (no H) gives a ketone; one carbon substituent …

• Drawing compound (A) as a saturated (non-aromatic) ring aldehyde instead of recognising that the C6H5- group was already a fully-formed, intact phenyl (aromatic) substituent BEFORE …