4. A chemist devised the following synthetic schemes. Some of the sequences will

Question

4. A chemist devised the following synthetic schemes. Some of the sequences will give reasonable yields of the indicated product, but others either will not work at all or will give low yields. Identify those sequences that will not give reasonable yields, and explain why a) COOC,H()CH,ONa (2) (CH3)3CBr COOC2Hs HC- C(CH3)3 COoC2Hs CH COOC2Hs (1) dil. NaOH (2) H,O (3) heat 0 (1)C H ONa (2) BrCH-C 0 CH CCH2COoC,Hs (1) dil. NaOH (2) H0 (3) heat C2H ONa CH-C-CH2 (1) dil. NaOH CH2C-CH2 CH (2) HO (3) heat

Explanation / Answer

step a) will give low yield, as you can see the product in the first step cannot be attacked
by the reagent as it very heavy and bulky.
step b) will give a high yield since the attacking enolate ion is stable, the reaction will proceed
step c) will not give rise to the given final product.
same thing goes for step d), however the starting reactant will not give rise to the product
in the first step. (and in second step of course !)
step e) the final product mentioned is wrong again

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