The IUPAC nomenclature of compound CH3CH2COOCH2CH3 is

The compound CH3CH2COOCH2CH3 is named using the IUPAC nomenclature system, which follows a set of rules to name organic compounds. The first step is to identify the longest continuous carbon chain, which in this case is a five-carbon chain, so the parent name is pentanoate. The chain has two substituents, which are ethyl and methyl groups, located on the second and fourth carbon, respectively. The complete name of the compound is ethyl 4-methylpentanoate. Therefore, the correct option is "ethyl butanoate."