Question

1. Write the equation that illustrates in situ preparation in this experiment. (2)
2. What gas will the gas trap prevent from escaping into the lab? (1)
3. Write the equation for the reaction between 1,3-butadiene and maleic anhydride. (2)
4. Draw the probable mechanism for the reaction if question 2. Indicate the diene and the dienophile. (3)
5. What is the purpose of adding water to the reaction mixture during reflux? (1)
6. Propose a mechanism for the hydrolysis of 4-cyclohexene-cis-1,2-dicarboxylic anhydride to 4-cyclohexene-cis-1,2-dicarboxylic acid. (2)
7. Define the following terms: (4)
8. In situ
9. Diene
10. Dienophile
11. Cycloaddition
12. Write the reactions for the two (2) characterization tests for unsaturation. (2)
13. Determine the limiting reagent, then calculate the theoretical yield of the FINAL product, 4-cyclohexene-cis-1,2-dicarboxylic acid. (3)

Answer 1

2. The Gas trap can prevent the escape of certain gases into the laboratory such as .These all are acid gases or acid-forming gases.

3.

4.

5. Water is added to the reaction mixture to HYDROLYSE the product obtained in this reaction to diacid.

7.

• In-situ- The term represents something that is happening 'within' the reaction medium.
• Diene- Generally in a Diels-Alder reaction,a Diene is a compound which has 2-Double bonds(so this is the ELECTRON RICH substance)  with-in carbon atoms.HOMO of the Dinene participates in Diels-Alder reaction.
• Dienophile-In a Diels-Alder reaction,compound which is an Alkene and ELECTRON POOR substance is called Dienophile.

8. Tests For Unsaturation-

• Bromine -Water test- Unknown Compound + solvent, if the Red color of Bromine discharges,then unsaturation present.if White precipitation is obtained , then Phenol is present.
• Baeyer test- This test is to determine the presence of double or triple bonds. The unsaturated compounds are oxidised by in basic medium forming syn-diol.

9.The Limiting reagent in this Cycloaddition reaction is generally Maleic-Anhydride,

Theoretical Yield=1.11 g of 4-Cyclohexene-cis-1,2-dicarboxylic Acid.