$PhCHO + Ph \cdot CHO \xrightarrow[in\,\,{{D}_{2}}O]{NaOD} A + \begin{matrix} O \\ || \\ Ph-C-{{O}^{-}} \\ \end{matrix}$$\left( Ph\right.$ is $\left.- C _{6} H _{5}\right)$

$C{H_3}COON{H_4}\xrightarrow{\Delta }X\,\xrightarrow{{{P_2}{O_5}}}\,Y\,\xrightarrow{{{H_2}O/{H^ + }}}\,Z$
