The thermogravimetric analysis of several coprecipitated zinc-copper oxalates in nitrogen is reported. The thermal decompositions of these mixed oxalates show a separate single step for dehydration and decomposition in the mass loss versus temperature curve. It is found that the onset temperature decreases with composition. For example, it decreases from 380 ~ for zinc oxalate to 260 ~ for copper oxalate. The end-product is mixed oxides and copper metal. These studies indicate the formation of an interpenetrating structure or mixed crystals during coprecipitation. Rate parameters have been calculated for dehydration and decomposition.The purpose of the present investigation was to study the effect of coprecipitated copper oxalate on the decomposition temperature of zinc oxalate in nitrogen with a view to elucidating the nature of these materials. Material and methodMixed oxalates of zinc and copper were prepared by a coprecipitation method. The copper and zinc contents of the mixed oxalates were determined by conventional chemical methods. Th e compositions showed some deviation from the proportions of the two salt solutions taken.The dehydration and decomposition temperatures of these mixed oxalates in nitrogen were determined in a thermogravimetric balance using a McBain-Baker type quartz spring [l ]. This had a sensitivity of 5.6 mg/mm extension and required only about 25 mg of sample for investigation. The extension of the spring was measured with a travelling microscope every 2 rain, while the temperature of the furnace was increased at a constant rate of about 5~ by means of a programming system described separately. The thermal analysis was carried out in flowing nitrogen gas, which was purified by passage through alkaline pyrogallol solution followed by moisture traps (a calcium chloride tower and silica gel drying tube). Results and discussionDehydration and decomposition temperatures reproducible within _+ 1.5 ~ were obtained. The results were plotted as percent weight loss against temperature.

Background: Biginelli reaction is the most well-known and widely studied multicomponent reaction used for the direct synthesis of many biologically active 3,4-dihydropyrimidin-2(1H)-ones and their derivatives by reacting a β-keto ester/1,3- dicarbonyl compound, an aldehyde, and urea. It was catalyzed by different Bronsted and Lewis acids. Methods: The catalytic effect of different metal chloride such as sodium, potassium, magnesium, stannous, ferric, manganese, cupric, nickel, cobalt, and zinc chlorides in absence and presence of acetic acid were studied. Results: The zinc, ferric, cupric, and cobalt chlorides were found to be more effective catalysts for Biginelli reaction at room temperature. The yield of reaction was increases with temperature for all catalytic system. Acetophenone, cyclohexanone, acetyl acetone, and different β-ketoesters forming tetrahedropyrimidine in moderate to good yield by using zinc chloride catalyst at room temperature in acetic acid. The efficiency of the catalyst was studied by treating different substituted aldehydes with 1,3-dicarbonyl compounds and urea at room temperature Results: The zinc, ferric, cupric, and cobalt chlorides were found to be more effective catalysts for Biginelli reaction at room temperature. The yield of reaction was increases with temperature for all catalytic system. Acetophenone, cyclohexanone, acetyl acetone, and different β-ketoesters forming tetrahedropyrimidine in moderate to good yield by using zinc chloride catalyst at room temperature in acetic acid. The efficiency of the catalyst was studied by treating different substituted aldehydes with 1,3-dicarbonyl compounds and urea at room temperature. Conclusion: The zinc chloride in acetic acid found to be effective greener catalyst system for Biginelli reaction.