$\left. \begin{gathered}
(A)\,\,\xrightarrow{{PB{r_3}}}\,(C)\,\xrightarrow{{Mg\,,\,ether}}Grignard\,\,reagent \hfill \\
(A)\,\,\xrightarrow[{{H_2}S{O_4}}]{{N{a_2}C{r_2}{O_7}}}\,(B) \hfill \\
\end{gathered} \right\}$ $ \to \,(D)\xrightarrow{{{H_3}{O^ \oplus }}}$ $(3,4-$ ડાયમિથાઇલ $3-$ હેકઝાનોલ l$)$
$I.\,\,C{H_2} = CH - C{H_3} + \,{H_2}O\,\xrightarrow{{{H^ + }}}$
$II. \,\,C{H_3} - CHO\,\xrightarrow[{(ii)\,{H_2}O}]{{(i)\,C{H_3}MgI}}$
$III. \,\, C{H_2}O\,\xrightarrow[{(ii)\,{H_2}O}]{{(i)\,{C_2}{H_5}MgI}}$
$IV.\,\,C{H_2} = CH - C{H_3}\,\xrightarrow{{KMn{O_4}}}$