Q.2 Ethylbutyrate is responsible for the odor of pineapple. Which one of the following is the structure
of ethyl butyrate?

Ethyl butyrate (ethyl butanoate) is the ester formed from butyric acid and ethanol, with structure CH₃CH₂CH₂C(=O)OCH₂CH₃.​
Among the given options, the correct structure is option (A), which shows the butyrate acyl part attached to an ethoxy group via an ester linkage.

Correct structure of ethyl butyrate

Ethyl butyrate is an ester of butyric acid (butanoic acid) and ethanol.​
Its structural formula is CH₃–CH₂–CH₂–C(=O)–O–CH₂–CH₃, where the four‑carbon butanoyl group (butyrate) is on the carbonyl side and the ethyl group is attached through oxygen.​

In the question’s options:

• Option (A) clearly shows a four‑carbon chain ending in a carbonyl carbon double‑bonded to oxygen, with an –O–CH₂–CH₃ group attached, exactly matching CH₃CH₂CH₂C(=O)OCH₂CH₃.

• Therefore, option (A) correctly represents ethyl butyrate (ethyl butanoate).​

Why the other options are wrong

Each wrong option either breaks the ester pattern or misplaces the ethyl/butyrate parts.

• Option (B):

  • Shows a carbonyl carbon with two carbon chains attached directly and the oxygen not in the –C(=O)–O–R ester arrangement.

  • This corresponds more to a ketone‑like framework rather than an ester such as ethyl butyrate.​

• Option (C):

  • Displays the carbonyl group attached to an –O–alkyl on one side and a longer alkyl chain on the other, making the acyl portion longer than four carbons.

  • Hence the acid part is not butanoic acid, so it cannot be ethyl butyrate (the acyl fragment must be butanoyl: CH₃CH₂CH₂CO–).​

• Option (D):

  • Has an ether‑like C–O–C linkage with no carbonyl adjacent to the oxygen, so it is a simple ether, not an ester.

  • Since esters require the –COO– motif, this structure cannot represent ethyl butyrate.​

Key concepts for identifying esters in MCQs

Recognizing ester structures quickly helps in such questions about fruity esters like ethyl butyrate responsible for pineapple aroma.​

• An ester always contains the –C(=O)–O– linkage between two carbon chains.​

• The acyl part (from the carboxylic acid) is on the carbonyl side; in ethyl butyrate, this must be a four‑carbon butanoyl group (CH₃CH₂CH₂CO–).​

• The alkoxy part (from the alcohol) is on the oxygen side; here, it must be an ethoxy group –O–CH₂–CH₃.​

Using these points, option (A) is quickly confirmed as the only structure consistent with the name ethyl butyrate.

SEO‑friendly introduction

The structure of ethyl butyrate is a classic concept in organic chemistry MCQs because this ester is responsible for the characteristic pineapple‑like odor found in many flavorings.​
Understanding how its IUPAC name (ethyl butanoate), carbon skeleton, and ester functional group fit together allows students to quickly pick the correct option and avoid common traps involving ketones, ethers, or esters with the wrong chain length.​