$1$ $\,.\,\,\,C{H_3}\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \,\, - \,\,H\,\,\,\,\,\,\,\,\,\,\,\,\,$
$2$ $\,.\,\,\,C{H_3}\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \,\, - \,\,C{H_3}\,\,\,\,\,\,\,\,\,$
$3$ $\,.\,\,C{H_3}\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \,\, - \,\,C{H_2}\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \,\, - \,\,H\,\,\,\,\,\,$
$4$ $\,.\,\,C{H_3}\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \, - \,\,C{H_2}\, - \,\mathop C\limits_{\mathop {||}\limits_O } \, - \,\,C{H_3}$

$\underset{(1)}{\mathop{C{{H}_{3}}C{{H}_{2}}CHO}}\,$
$\underset{(2)}{\mathop{\begin{matrix}
O \\
|| \\
C{{H}_{3}}-C-C{{H}_{3}} \\
\end{matrix}}}\,$
$\underset{(3)}{\mathop{C{{H}_{3}}-CH=CH-OH}}\,$

