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sara stive

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  1. I want to synthesis a polyimide from a diamine and a dianhydride in lab scale, in two-step synthesis route for fabrication the polyimides, in the second step, acetic anhydride and pyridine are added to the reaction mixture to separate the H2O and formed polyimide from polyamic acid, but how determined the amounts of this reagents?
  2. In this work, fluorescein was incorporated with an equal molar of 1-chloro-4-nitrobenzene and double potassium carbonate (molar ratio), the solvent of this reaction is dimethylacetamide (50 ml for 5 g of fluorescein). The solution was stirred in at 110 °C for 24 h, after that cooled to the room temperature and precipitated in cold water, but a solid, similar to potassium carbonate, remains at the bottom of the reaction vessel, and the efficiency is very low (25%). I don't know the cause of this problem. This is the structure that I expected for first stage: In the next step the solid that was obtained from the previous stage, incorporated with 10% Pd/C and methanol. 30 eq hydrazine monohydrate was added dropwise and the solution refluxed at 50 °C for 12 h. After that the solution was filtered to separated catalyst and the crystals of diamine was obtained, but the efficiency of this stage is very low too. who can help me?
  3. In this work, fluorescein was incorporated with an equal molar of 1-chloro-4-nitrobenzene and double potassium carbonate (molar ratio), the solvent of this reaction is dimethylacetamide (50 ml for 5 g of fluorescein). The solution was stirred in at 110 °C for 24 h, after that cooled to the room temperature and precipitated in cold water, but a solid, similar to potassium carbonate, remains at the bottom of the reaction vessel, and the efficiency is very low (25%). I don't know the cause of this problem. This is the structure that I expected for first stage: In the next step the solid that was obtained from the previous stage, incorporated with 10% Pd/C and methanol. 30 eq hydrazine monohydrate was added dropwise and the solution refluxed at 50 °C for 12 h. After that the solution was filtered to separated catalyst and the crystals of diamine was obtained, but the efficiency of this stage is very low too. who can help me?
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