Question

When ethyl acetoacetate (ch3coch2co2ch2ch3) is treated with one equivalent of ch3mgbr, a gas is evolved from the reaction mixture, and after adding aqueous acid, ethyl acetoacetate is recovered in high yield. identify the gas formed and explain why the starting material was recovered in this reaction. be sure to answer all parts. the gas formed is: o2 h2 ch4 co2 this occurs because: addition of a methyl group through nucleophilic addition destabilizes the ester group. because of the acidic proton, ch3mgbr reacts as a base and proton transfer occurs rather than nucleophilic addition. aqueous acid adds an oxygen to the carbanion formed releasing h2 gas. addition of aqueous acid disrupts the anhydride bond which reforms after decarboxylation?

Answer 1

The protons of methylene group between the two carbonyl groups in ethylacetoacetate are acidic in nature. When compounds containing such acidic protons are treated with bases the loose proton and form enolates.
In this particular example when ethylacetoacetate is reacted with methyl magnesium bromide, the methyl group abstracts the acidic proton and converts into methane gas. The enolate when hydrolyzed is again converted into ethylacetoacetate as shown below,