Nitrobenzaldehyde Synthesis

M-nitrobenzaldehyde is an important organic synthesis intermediates. However, the industrial synthesis of m-nitrobenzaldehyde still remain in the traditional method of mixing acid nitration, this brings great pressure to environment. Based on the actual industrial production, two novel synthetic methods of m-nirobenzaldehyde were studied:(1)The m-nitrobenzaldehyde was synthesized when m-nitrotoluene was used as raw material through bromination, hydrolysis, oxidation. The three-step reaction conditions were optimized respectively. The optimized conditions were as follows:①n (m-nitrotoluene):n(potassium bromate):n(Sodium bisulfite) was 1:2.5:2.5, bromination time was 4h, bromination temperature was 70℃, n(bromide product):n(sodium carbonate) was 1:2, hydrolysis time was 7h, hydrolysis temperature was 100℃, oxidation temperature was 100℃. Under this conditions the yield of crued m-nitrobenzaldehyde could reach 48.2%.②n(m-nitrotoluene):n(hydrobromide):n(hydrogen peroxide) was 1:3:3, bromination time was 4h, bromination temperature was 62℃, The other conditions were the same as the system of potassium bromate, the yield of crude m-nitrobenzaldehyde could reach 35%.After steam distillation or the availability of ethanol-recrystalline, the purity of m-nitrobenzaldehyde was up to 99%.(2) M-nitrobenzaldehyde was prepared from m-nitrotoluene via oxidation by Mn₂O₃ when sulphuric acid was used as the reaction medium. The results showed that the yield of m-nitrobenzaldehyde was up to 65.6 % when n(m-nitrotoluene):n(Mn₂O₃): was 1:1.5; reaction temperature was 90℃; reaction time was 7h.