$\begin{array}{*{20}{c}} {O = CH - C{H_2} - CH - CHO} \\ {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|} \\ {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,H - C = O\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \end{array}$