Study On The New Synthetic Technology Of O-nitrobenzaldehyde

o-Nitrobenzaldehyde is an important organic intermediate,which is mainly used in the fields of medicine,pesticide and other organic synthesis.Especially,o-nitrobenzaldehyde is widely used in drug synthesis,which is the key intermediate for the synthesis of cardiovascular disease drugs,such as nitropyridine,nisoldipine and encarbamide.Its market requirement increases year by year.At present,the industrial synthesis method of o-nitrobenzaldehyde was that o-nitrotoluene was brominated to o-nitrobenzyl bromide by bromine,then hydrolyzed to o-nitrobenzyl alcohol by potassium carbonate solution,finally,o-nitrobenzyl alcohol was oxidized to o-nitrobenzaldehyde by dilute nitric acid.Wastewater containing bromine in this method was difficult to be treated,which had seriously polluted the environment.With the improvement of environmental requirements,it had become the research direction to avoid the use of bromine.In addition,the price of bromine had rised sharply in recent years,which was from 20 thousands up to nearly 50 thousands yuan per ton,causing the high cost of production and high production pressure.Therefore,more and more companies tried to explore new bromination methods to avoid using bromine.Based on the above situations and referenced the related literatures,we designed three different synthetic routes which effectively avoided using bromine.The experimental conditions of three synthetic routes were researched by using orthogonal experiment.The first route was that o-nitrotoluene was bromided by NaBr under the effect of light irradiation and chlorine,o-nitrobenzal bromide and o-nitrobenzyl bromide were obtained,then were hydrolyzed to obtain o-nitrobenzaldehyde and o-nitrobenzyl alcohol,finally,pure o-nitrobenzaldehyde was obtained after separation the products.The second route was that o-nitrotoluene was bromided by HBr under the effect of light irradiation and H2O2,o-nitrobenzal bromide was obtained,then was hydrolyzed to obtain o-nitrobenzaldehyde by acetic acid,at the same time,the by-product(acetyl bromide)was a gas which could be separated automatically.The third route was that benzyl chloride was nitrified by mixed acid(sulfuric acid and nitric acid)to produce o-,m-,p-nitrobenzyl chloride,then were hydrolyzed by alkaline to obtain o-and p-nitrobenzyl alcohol,m-nitrobenzyl chloride could not been hydrolyzed,so it was separated,o-and p-nitrobenzyl alcohol were oxidized by nitric acid to become o-and p-nitrobenzaldehyde,which was separated to obtain o-nitrobenzaldehyde and p-nitrobenzaldehyde.The three synthetic routes have their own advantages and disadvantages.The total yield was high in the first route,and the by-product o-nitrobenzyl alcohol was also used for the synthesis of o-nitrobenzaldehyde.However,chlorine is inconvenient to use,and expensive equipments were required in production.The total yield was also high in the second route.The target product was easy to obtain,but the reaction time was longer.The total yield was high in the third route.The by-products(p-nitrobenzaldehyde and m-nitrobenzyl chloride)were important intermediates of certain drugs,which had a certain economic value.However,benzyl chloride was inconvenient to use,because it had strong toxicity.In short,the three routes all had some disadvantages in production.Compared with other synthetic routes,the second route was more suitable for industrial production,but some of the synthesis details still need to be further optimized.