One-pot Synthesis of Benzaldehyde Semicarbazone

Benzaldehyde semicarbazone was prepared from hydrazine hydrate,urea and benzaldehyde by one pot synthesis .According to this process, the intermediate semicarbazide was not isolated from the reaction mixture as semicarbazide HCl but directly reacted with benzaldehyde to give semicarbazone,and the waste liquid containing hydrazine was not formed.Thus, at optimum operation conditions, hydrazine hydrate(50%),urea and benzaldehyde in mole ratio 1 0∶2 0∶0 8 were used,hydrazine hydrate and ure reacted at 98-101 ℃for 3-4 h to form semicarbazide, then,at pH 3-4 and room temperature,benzaldehyde was dropped in during 1.5h,the mixture was further stirred for 2h and finally refluxed for 1h. Yield of the semicarbazone was 98.0%.