The condensed, bond line and complete formulae of $n$-butane are respectively.

' $X$ ' is the isomer of $\mathrm{C}_6 \mathrm{H}_{14}$. It has four primary carbons and two tertiary carbons, ' $X$ ' can be prepared from which of the following reactions?

$$ \text { What are } X \text { and } Y \text { in the following reaction sequence? } $$

$$ \text { Isopentane } \xrightarrow{\mathrm{KMnO}_4} X \xrightarrow[358 \mathrm{~K}]{20 \% \mathrm{H}_3 \mathrm{PO}_4} Y $$

What are $X$ and $Y$ respectively in the following reactions?