Date of lab: 04/25/05
Date submitted: 05/09/05
Synthesis of Co(acac-NO2)3
In this lab, Co(acac·NO2)3 is synthesized using the Co(acac)3 complex produced in Experiment 2. The Co(acac)3 complex is used as a reagent instead of acacH because acacH cannot be directly converted to 3-nitroacetylacetone. Since Co(acac)3 is not stable in HNO3, Cu(NO3)2 and acetic anhydride are used in this reaction to produce the final product, Co(acac·NO2)3. The exact mechanism of the reaction is unknown, however, it is believed to proceed as follows:
Data and Calculations
Table 1: Measurements of weights and melting point
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Allowing the reaction to occur in ice separated the Co(acac-NO2)3 (as an oil) from the other reagents, and ethanol was used to solidify this oil.
3) The calculated theoretical yield of Co(acac-NO2)3 is 0.46 grams. 0.3510 grams was produced, which is about a 76% yield. This low percentage yield could be due to loss of some of the product when transferring the solution from the Erlenmeyer flask to the ice-filled beaker to the Gooch funnel. It was difficult to completely transfer all the solution from one container to another. Decantation of the reagents from the oil was especially difficult, and a small volume of the oil was accidentally decanted along with reagent solution, resulting in a lower yield. Product was also likely to have been lost in the filtration step. Not all of the solid could be transferred from the solution in the beaker to the filter paper.
4) The observed melting point of the product was 182-187°C. This is lower than the literature MP value of 198°C for Co(acac-NO2)3, indicating that the final product was not pure. This impurity could be due to presence of acetic acid or sodium acetate in the final product (resulting from incomplete reaction), or due to inadequate rinsing of the final product