$word_{count}$: 200

Ozonolysis is the most important reaction for JEE structure determination. Forward ozonolysis: C=C is cleaved, each carbon becomes C=O. With reductive workup $\frac{Zn}{H2O}$: =CH2 → HCHO, =CHR → RCHO, =CR2 → R2CO. With oxidative workup (H2O2): =CH2 → CO2, =CHR → RCOOH, =CR2 → R2CO. Reverse ozonolysis: given products, remove C=O from each and connect the carbons with C=C to reconstruct the original alkene. For cyclic alkenes: ozonolysis opens the ring, producing a single dialdehyde/diketone product (not two separate fragments). For alkynes: ozonolysis gives carboxylic acids (terminal C gives HCOOH → CO2). JEE frequently tests: (1) predict ozonolysis products from a given alkene, (2) deduce the original structure from products, (3) distinguish between isomeric alkenes by their different ozonolysis products. The systematic approach: identify the C=C bond, replace it with two C=O groups, and check that the carbon count matches.