`C_(5)H_(10)` represents three isomeric alkenes `A_(1),A_(2)` and `A_(3)`. Each on hydrogeration gives `2-`methylbutane. `A_(1)` and `A_(2)` on oxymercuration-demercuration give the same `3^(o)` alcohol. `A_(2)` and `A_(3)` on hydroboration oxidation give different `1^(o)` alcohol. Assign structures to `A_(1), A_(2)` and `A_(3)` and explain the reactions.

Answer

`A_(1),A_(2)`orA_(3)overset(H_(2))rarrH_(3)Cunderset(CH_(3))underset(|)CHCH_(2)CH_(3)`
This shows that each of `A_(3),A_(2)` and `A_(3)` have same `C-chain: only position of `(C=C)` is to be decided.
`A_(1),A_(2)`underset("demercuration")overset("oxymercuration")rarr3^(o)` alcohol
hecne `A_(1)` and `A_(2)` have `(##ALN_CHM_C09(I)_E01_081_A01##)` groupings.
`A_(2)` and `A_(3)`overset("hydroboration oxidation")rarr1^(o)` alcohol
This indicates presence of `(CH_(2=)` grouping at the terminal. Hence,
`A_(1)` is `CH_(3)underset(CH_(3))underset(|)C=CHCH_(3)`
`A_(2)` is CH_(3)CH_(2)underset(CH_(3))underset(|)C=CH_(2)`
`A_(3)` is CH_(3)underset(CH_(3))underset(|)CHCH=CH_(2)`
`A_(1)` or `A_(2) underset("demercuration")overset("oxymercuration")rarrCH_(3)underset(CH_(3))underset(|)overset(OH)overset(|)(C)CH_(2)CH_(3) 3^(o)` alcohol `(X)`
`A_(2)underset("oxidation")overset("hydroboration")rarr CH_(3)underset(CH_(3))underset(|)CHCH_(2)CH_(2)OH 1^(o)` alchohol `(Z)`
`Y` and `Z` are different `1^(o)` alcohols.