Final answer:
In methyl butyrate, the two electrophilic carbons are the carbonyl carbon of the ester group and the alpha carbon, which is directly connected to the carbonyl carbon via an oxygen atom.
Step-by-step explanation:
The ester methyl butyrate consists of a butyric acid skeleton where the hydroxyl group is replaced by a methyl group. In esters, the electrophilic carbons are the ones involved in the carbonyl group (C=O) and the carbon to which the oxygen of the methoxy (O-CH3) group is attached. In the case of methyl butyrate, these carbons are the ones in the C=O group and the carbon of the acid moiety attached to that oxygen.
We're looking for the carbons that have a partial positive charge and can be targeted by nucleophiles. In methyl butyrate (methyl ester of butyric acid), the two electrophilic carbons are the one in the carbonyl group (C=O, due to the delta+ charge on the carbon) and the one directly connected to this through an oxygen (the alpha carbon).