Question

1.     How are the E1 and E1cB reaction mechanisms different from each other? Draw an example of the reaction mechanism for each one to help illustrate your answer.

(5 marks)

 

2.     Briefly explain how the experiment about the comparison of the heats of hydrogenation between cyclohexane, cyclohexene, 1,3-cyclohexadiene and benzene is able to indicate the unusual stability of benzene?                                                                    (10 marks)

 

Answer 1

The one-step mechanism is known as the E2 reaction, and the two-step mechanism is known as the E1 reaction. The numbers refer not to the number of steps in the mechanism, but rather to the kinetics of the reaction: E2 is bimolecular (second-order) while E1 is unimolecular.

E1

E1cB reaction