Page 27 Flashcards
What does it mean for a reaction to be stereoselective?
A: A reaction is stereoselective when it forms predominantly or exclusively one stereoisomer when two or more are possible.
Why is the E2 reaction considered stereoselective?
A: Because it preferentially forms the more stable stereoisomer, usually the trans alkene over the cis alkene.
In an E2 reaction, which product is typically the major product?
A: The trans alkene (more stable due to reduced steric interactions).
What is the minor product in an E2 reaction involving stereoisomers?
A: The cis alkene (less stable due to increased steric interactions).
What role does the base play in E2 stereoselectivity?
A: The base removes a proton, allowing for elimination, and influences the formation of the more stable stereoisomer.
What is the starting compound in the example reaction?
A: A halogenated alkane with a β-hydrogen (in this case, compound X with a Br leaving group).
Why is the trans alkene (Y) more stable than the cis alkene (Z)?
A: The trans alkene has less steric hindrance between substituents on opposite sides of the double bond.
What type of solvent favors E2 reactions and enhances stereoselectivity?
A: Polar aprotic solvents.
What happens to the leaving group in an E2 reaction?
A: It departs simultaneously as the β-hydrogen is removed, forming the double bond.
What is the relationship between the stability of the transition state and the stereoselectivity of the E2 reaction?
A: The more stable the transition state, the more likely the reaction will produce the trans alkene as the major product.
