Study On Interface Effect On Organic Synthesis For Several Compounds Under Microwave

The microwave technology is widely used in in organic synthesis.In a largenumber of published papers, microwave heating has been shown to dramatically reducereaction times, increase product yields, and enhance product purities by reducingunwanted side-reactions compared with conventional heating.Microwave irradiationproduces efcient internal heating by direct coupling of microwave energy with themolecules that are present in the reaction mixture.The ability of a specific material orsolvent to convert microwave energy into heat at a given frequency and temperature isdetermined by the so-called loss tangent.In this paper, the synthesis of ethyl benzoate and Isopropyl salicylate was carriedout in microwave heating and conventional heating,and the effect of activated carbon,silica, carborundum and ceramic powder was debated.The main reacher and results are as below:In the first part, the effect of activated carbon, silica, carborundum and ceramicpowder to the temperature of five solvents(cyclohexane, chlorobenzene, pyridine,water,methanol) in microwave was debated. The powders of activated carbon, silicaand carborundum incresed the temperature of solvents, and shorted the time of boiling.The poorer the polarity of solvents, the greater the effect.In part two, the synthesis of ethyl benzoate and Isopropyl salicylate was carried out,and the effect of activated carbon, silica, carborundum and ceramic powder was debatedby contrasting the yields of reactions in microwave heating and conventional heating.Because of the strong microwave absorption of activated carbon, the heating rateof nonpolar solvents that containing activated carbon was more rapid. On the other hand,activated carbon could also absorb reaction substrate which reduced the reactionconversion. There are many hydroxyl groups at the surface of silicon, which couldabsorb mirowave strongly. Since the absorption of these groups to acid, the reactionswere inhibited in microwave heating and conventional heating. The SiC material couldnot only absorb microwave bur also increase contact area. The conversion of reactionsin both microwave and conventional heating was increased by adding SiC to reactor.The reactions were promoted by adding ceramic powder into reactors for the increasingof contact area.