A: Bromination of trans-stilbene (materials used in part A: 10%bromine-dichloromethane solution, trans-stilbene, dichloromethane, cyclohexene)
B: Preparation of dephenylacetylene from dibromostilbene (materials used in B: ethylene glycol, ethanol, dibromostilbene, potassium hydroxide)
Answer the following questions:
1. Provide the whole mechanisms of the part A and B synthesis.
2. What substance is responsible for this smoke; during reflux in part the B, the reaction smokes.
3. Explain why is the cyclohexene is used in the first step and why does it not contaminate the product?
4. What is this product and why does it form preferentially to 2-butyne when this synthetic sequence is performed starting with the 2-butene rather than stilbene, another product other than 2-butyneis the major product?