image $\xrightarrow{{A{c_2}O}}A\mathop {\xrightarrow{{B{r_2}}}}\limits_{C{H_3}COOH} B\mathop {\xrightarrow{{{H_2}O}}}\limits_{{H^ + }} C$ would be

image$\mathop {\xrightarrow{{NaN{O_2}}}}\limits_{HCl} A\,\,\xrightarrow{{CuCN}}B\,\,\mathop {\xrightarrow{{{H_2}}}}\limits_{Ni} C\,\,\xrightarrow{{HN{O_2}}}D$