The Synthesis Study Of Selenourea And Its Applications

Selenourea is an important intermediate for organic synthesis .In this experiment ,it is prepared through three steps on the material of selenium powder, sodium borohydride, thiourea, iodomethane and anhydrous ethanol.In this experiment , products are identified by measuring melting points, element analysis and IR ,and every step is optimized. In the first step, sodium hydrogen selenide is prepared on the material of selenium powder and sodium borohydride in solvent anhydrous ethanol. The influence of adding ways ,cooling temperature of anhydrous ethanol, the ratio of sodium borohydride and selenium and adding ways of sodium borohydride are preliminarily researched . Preferable synthesis technical conditions for sodium hydrogen selenide are gained by large numbers of single ingredient experiments, which are T= -8～-11℃, n(NaBH4)∶n(Se)=1.21∶1, 78% of sodium borohydride is firstly added , the other 22% is added when the first is nearly completely reacted. In the second step, Methyl aminomethanimidothioate hydroiodide is prepared on the material of thiourea and iodomethane in solvent anhydrous ethanol. The influence of light , the ratio of iodomethane and thiourea , reaction time ,and solvent on the yield of Methyl aminomethanimidothioate hydroiodide is preliminarily studied, preferable technical conditions in solvent anhydrous ethanol are gained by single ingredient experiments, which are n(CH3I)∶n (NH2CSNH2)=1.24∶1, reacted for two hours in room temperature, then refluence for one hour and the whole process in darkness. The yield according to selenourea is 76% in preferable technical conditions. comparing t he reaction effect with adopting methanol or water as solvent, and draw a conclusion that the effect of using methanol is better than using anhydrous ethanol or water as solvent, the yield according to selenourea is up to 81%. In the third step , sodium hydrogen selenide and Methyl aminomethanimidothioate hydroiodide are added together to get selenourea, The influence of reaction time and temperature on the yield of selenourea is studied. Preferable synthesis technical conditions for selenourea are getted by single ingredient experiments, The conditions are: refluence for 2.5 hours in dry and no oxygen condition, then adding Glacial acetic acid , filtration in decompression, and distillation in temperature near to 24℃and degree of vacuum near to 15mmHg. Colourless and acerate selenourea crystal is achieved in this condition, and all works are made in darkness, topmost yield on the base of thiourea is up to 81%. Finally selenoura together with ethyl chloroacetate is used to get 2-amino-2-selenazolin-4-one.