That compound is called an ester. In naming an ester, we should identify which part belongs to the carboxylate group (parent acid) and which part is the R group (parent alcohol) The parent acid is the one with a carbonyl group or the one who has the C doubly bonded to O. In our problem, we can see that the C=O is the 8th C if you start counting from the left. This is now the Parent acid. Since it contains 7 carbon, we call it heptanoate. The R group attached contains 3 carbons thus we call it a propyl group. So now we can name the compound as: Propyl heptanoate.
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the o is suppose to be over the single c