Ozonolysis of an alkene involves the cleavage of the carbon-carbon double bond to form carbonyl compounds . To deduce the structure of the original alkene 'X', we can work backwards by removing the oxygen atoms from the given products (formaldehyde and 2-methylpropanal) and joining their respective carbonyl carbon atoms with a double bond.

1. Structure of Formaldehyde: $\text{CH}_2\text{=O}$
2. Structure of 2-Methylpropanal: $\text{O=CH-CH(CH}_3)_2$

Joining the double-bonded carbons yields the alkene: $\text{CH}_2\text{=CH-CH(CH}_3)_2$. Numbering the principal carbon chain from the end nearer to the double bond gives the IUPAC name 3-Methylbut-1-ene .