Study On Electrohalogenation Of Some Aromatic Compounds

Aromatic halides are a very important class of organic synthesis intermediates,occupying an important position in the chemical,biological,electronic,pharmaceutical and other industrial and agricultural fields.However,traditional chemical preparation methods have disadvantages such as harsh reaction conditions,expensive raw materials such as halogen sources and catalysts,dangerous operating conditions,complex process flow,and relatively poor selectivity.The“three wastes”produced will cause serious environmental pollution,which is not in line with the current Requirements for green chemicals.The electrochemical halogenation method directly uses electrons as oxidants and inexpensive and non-toxic inorganic halide salts as halogen sources.The reaction conditions are mild and no additional heating and pressure equipment is required.The production process is simple and presents a very good industrial prospect.In this paper,the electrohalogenation reaction of aromatic compounds and inorganic halide salts in the synthesis of aromatic halides is the research object,and the following two aspects are mainly studied.First,the electrohalogenation of synthesizing 2,4,5-trimethylchlorobenzene under constant current electrolysis conditions with trimethylbenzene and Na Cl was used as a template reaction,and the structure of the electrochemical reactor(with or without diaphragm)and anode material were investigated.,The effect of factors such as acidity,temperature,solvent,current density,diaphragm material,etc.,to obtain better electrohalogenation reaction conditions and a series of high-purity aromatic halides.The results show that:when the reaction temperature of electrohalogenation is 10℃,the reaction medium is acetonitrile and saturated sodium chloride solution is used,the current density is 300-400A/m~2,the cell voltage is 9.2V,and the cathode and anode plates are respectively highly active for hydrogen evolution.For example,carbon steel,stainless steel,platinum,titanium,etc.and DSA plates with high chlorine evolution activity,the use of two-chamber(with diaphragm)electrolytic cell,and the use of Nafion324 cation exchange membrane,the electrohalogenation reaction effect is better.At the same time,the kilogram scale was carried out for the diaphragm chlorination of trimethylbenzene,and the experimental results proved that it can be safely and effectively scaled up to kilogram scale preparation,and the industrial application prospect is broad.In order to further expand the application range of the electrohalogenation reaction system,we have investigated the applicability of a series of aromatic compound electrohalogenation reactions,which proves that the substrates of this reaction process have a wide range of applications and can effectively supply aromatic compounds,especially with electrons.The radical aromatic compound is halogenated.All the products prepared were confirmed and characterized by structural analysis by GC,HPLC and ~1H NMR.Secondly,in order to better explain the activity of the halogenation reaction and its positioning effect,this paper uses Gaussian density functional theory to analyze the natural bond orbital analysis,electrostatic potential analysis and frontier molecular orbital theory analysis of nine aromatic compounds.The specific behavior of the electrochemical reaction is studied,and the possible reaction mechanism is discussed and explained.Through analysis,the Gaussian calculation results are basically consistent with the actual experimental results,and the calculation method has high reference value in the localization and activity prediction of electro halogenation.