when fumaric acid is heated at 300degree celcus gives maleic anhydride explain
Answers
Answer:
Maleic acid (the cis isomer of the dicarboxylic acid C4H4O4) readily forms its anhydride on heating. Clayden's organic chemistry textbook mentions this as a point of distinction between it and fumaric acid (the trans isomer), which fails to dehydrate to its anhydride upon heating. However, I have discovered that at temperatures above 200 ∘C, fumaric acid forms maleic anhydride as well.
Explanation:
Some calculations (values from NIST) reveal that the formation of maleic anhydride and water from fumaric acid is an endothermic reaction (ΔH≈+65.28kJmol) but the change in entropy is positive (ΔS≈134.24Jmol⋅K). This means that the reaction becomes spontaneous for temperatures above 213∘C, but this is only "mildly" spontaneous (ΔG≈−5kJmol at 523 K). So, the use of a dehydrating agent to remove the water from the reaction mixture and drive the equilibrium forward (Le Chatelier's principle) is necessary.