Answer – An ester is an organic compound derived from a carboxylic acid and has the formula $\mathbf{R}\mathbf{–}\mathbf{COO}\mathbf{–}\mathbf{R}\mathbf{‘}$. An ether, on the other hand, is one that is derived from an alcohol and has the formula $\mathbf{R}\mathbf{–}\mathbf{O}\mathbf{–}\mathbf{R}\mathbf{‘}$.

Explanation: 

Esters and ethers are classes of organic compounds with distinct functional groups that define their structures.

Esters are obtained from carboxylic acids. They are usually formed when such an acid reacts with an alcohol in the presence of a catalyst (an inorganic acid). The reaction, as shown below, is thus known as esterification.

$$\begin{gathered} \mathrm{R}–\mathrm{COOH} + \mathrm{R}‘–\mathrm{OH} \stackrel{\mathrm{Inorganic} \mathrm{acid}}{\rightleftharpoons } \mathrm{R}–\mathrm{COO}–\mathrm{R}‘ + {\mathrm{H}}_2\mathrm{O} \\ \mathrm{Carboxylic} \mathrm{Alcohol} \mathrm{Ester} \mathrm{Water} \\ \mathrm{acid} \end{gathered}$$

The hydrogen of the carboxyl (–COOH) group of the acid gets replaced by the alkyl/aryl group (R’) of the alcohol to form an ester with the formula R–COO–R’. The ester produced will have the below structure:

One of the oxygen atoms of the –COO functional group is always double bonded to the carboxyl carbon. The other oxygen atom also shares one single bond with this carbon and another with the carbon of the alkyl/aryl group. One example of an ester is ethyl acetate (IUPAC name: ethyl ethanoate).

Ethers, on the other hand, are derived from alcohols. They are commonly produced using the Williamson’s (ether) synthesis, which involves an alkyl halide. Below is the simplified form of the reaction:

$$\begin{gathered} \mathrm{R}–\mathrm{O}–\mathrm{H} \underset{ 2. \mathrm{R}‘–\mathrm{X} (\mathrm{Alkyl} \mathrm{halide})}{\overset{1. \mathrm{Strong} \mathrm{base}}{\to }} \mathrm{R}–\mathrm{O}–\mathrm{R}‘ \\ \mathrm{Alcohol} \mathrm{Ether} \end{gathered}$$

1. In the presence of a strong base like sodium hydride (NaH), the alcohol becomes an alkoxide ion (R–O⁻).

2. A primary alkyl halide (in which the carbon linked to the halogen atom is linked to only one other carbon atom) is then introduced. This reacts with the alkoxide ion through SN₂ mechanism to form the ether (R–O–R’) with the following structure:

The oxygen atom of the –O– functional group shares one single bond each with a carbon atom of the alkyl/aryl group on either side. One example of an ether is diethyl ether (IUPAC name: ethoxyethane).

Popular Questions