image$\xrightarrow{{A{c_2}O}}A\mathop {\xrightarrow{{B{r_2}}}}\limits_{C{H_3}COOH} B\mathop {\xrightarrow{{{H_2}O}}}\limits_{{H^ + }} C$
${C_2}{H_5}N{H_2}\,\xrightarrow{{HN{O_2}}}a$
${C_2}{H_5}N{H_2}\,\xrightarrow{{{C_6}{H_5}CHO}}b$
${C_2}{H_5}N{H_2}\,\xrightarrow{{NOCl}}c$
${C_2}{H_5}N{H_2}\,\xrightarrow{{{C_6}{H_5}S{O_2}Cl}}d$