Question

Which of the following represents the ester functional group?

A. -COO-
B. -CHO
C. -COOH
D. C=O

Answer 1

Answer:

D. C=O

Explanation:

Esters are formed by the condensation of alcohols and acids with minus water. During the reaction, at least one -OH group is replaced by an O- alkyl group. The resulting compound is an ester and has a characteristic fruity smell. Its functional group is C=O

Answer 2

Answer: A. -COO-

Explanation:

Functional groups are specific group of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.

A. Esters have functional group $-O=C-OR$.

Example: methyl ethanoate with molecular formula $CH_3COOCH_3$

B. Aledydes have functional group $-O=CH$.

Example: Ethanal with molecular formula $CH_3CHO$

C. Acids have functional group $-O=C-OH$.

Example: Ethanoic acid with molecular formula $CH_3COOH$

D. Ketones have functional group $-C=O$.

Example: Propanone with molecular formula $CH_3COCH_3$