Identify the major products A and B respectively in the following set of reactions. [figure]
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Answer
(2) [figure]
Solution
[figure]
Conc. H2SO4 dehydrates the alcohol by E1 through the 3° carbocation; by Saytzeff rule the more substituted (endocyclic) alkene is the major product A.
[figure]
CH3COCl acetylates the O–H (ester formation) and pyridine removes HCl, so B is the acetate ester.
(1): exocyclic =CH2 alkene and a C-acetyl compound, so (1) is wrong
(2): endocyclic alkene A and the ester B, so (2) is correct
(3): exocyclic alkene and a C-acetyl compound, so (3) is wrong
(4): A is right but B is a C-acetyl compound, not the ester, so (4) is wrong
Answer: (2)