Assign structures for the following:
(a) An alkyne (X) has molecular formula `C_(5) H_(8)`. It reacts neither with sodamide nor with ammoniacal cuprous chloride.
(b) A hydrocarbon Y decolourises bromine water. On ozonolysis it gives 3-methyl butanal and formaldehyde. Give the name of the compound.
(c) A hydrocarbon (Z) has molecular formula `C_(8)H_(10)`. It does not decolourise bromine water and is oxidised to benzoic acid on heating with `K_(2)Cr_(2)O_(7)`. It can also have three other isomers A, B and C. Write the structures of Z, A, B and C.

Explanation

Alkyne X is `C_(5)H_(8)` . Since it does not react with sodamide or ammoniacal cuprous chloride, the triple bond cannot be terminal.
`therefore X= CH_(3)CH_(2)C = C CH_(3)` Pent-2-yne
(b) Hydrocarbon Y is alkene because it decolourises bromine water. From the products of ozonolysis, the structure of alkene can be predicted.
`underset("3-Methyl butanal")(CH_(3)underset(CH_(3))underset(|)CHCH_(2)overset(H)overset(|)C)= underset("Formaldehyde")(O+ O =overset(H)overset(|)C-H) to underset("4-Methylpent-1-ene")(CH_(3)underset(CH_(3))underset(|)CHCH_(2)CH= CH_(2))`
(c) Since it does not decolourise bromine water, it is arene. Its formula is