1 \(C{H_2}O - C{H_2}O\)
2 $\begin{array}{*{20}{c}}
\begin{gathered}
C{H_2}OH \hfill \\
\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \hfill \\
\end{gathered} \\
{C{H_2}OH}
\end{array}$
3 $\begin{array}{*{20}{c}}
\begin{gathered}
CHO \hfill \\
\, \,\, \,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \hfill \\
\end{gathered} \\
{CHO}
\end{array}$
4 $\begin{array}{*{20}{c}}
\begin{gathered}
C{H_2}OH \hfill \\
\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \hfill \\
\end{gathered} \\
{CHO}\,\,\,\,\,\,\,
\end{array}$