Question

7. Provide a complete, arrow-pushing mechanism for each of the reactions below.(7 pts. each) NaOH (aq) then heat (a) HO NaOH ini EtOH/H20 (b)

Answer 1

1) Answer: NaOH Heat (E)-chalcone This reaction is an example for aldol condensation Mechansim: 400 H OH Keto enol tautomersim Base abstracts a proton from the active methylene group carbon. The carbanion is in tautomerism (keto-enol) OH O H20 ch The carbanion nucleophilic attack at electrophilic carbonyl carbon to form B-hydroxy ketone Он о Heat - H20 The keto alcohol undergo dehydration on heating to produce a, B-unsaturated compound

2) Answer: HO NaOH EtOH/H20 H This reaction is called as Robinson's annulation which involves internal Michael addition followed by internal aldol condensation. Mechanism: Na En OH H HO ОН H20 The mechanism initiated by proton abstraction in presence of base. Michael addition takes place to get cyclic di-one. The di-one undergo internal aldol condensation to get the corresponding product.