Difference Between Ester and Ether

The key difference between ester and ether is that the functional group of an ester is –COO, whereas the functional group of an ether is –O-.

Ester and ether are organic molecules with oxygen atoms. Esters have the group –COO. Here, one oxygen atom is bonded to carbon with a double bond, and the other oxygen is bonded with a single bond. Since only three atoms connect with the carbon atom, it has a trigonal planar geometry around it. Furthermore, the carbon atom is sp² hybridized. Moreover, an ester is a carboxylic acid derivative. An ether, on the other hand, has an oxygen atom with two single bonds with two alkyl or aryl groups. The oxygen atom has two lone electron pairs as well.

CONTENTS

1. Overview and Key Difference
2. What is Ester
3. What is Ether
4. Side by Side Comparison – Ester vs Ether in Tabular Form
5. Summary

What is Ester?

An ester is an organic compound that forms by the reaction of an oxoacid with a hydroxyl compound (such as alcohol and phenol). It resembles a carboxylic acid having its hydrogen atom of –COOH group replaced by an alkyl or aryl group. Esters are polar molecules, but their boiling points are lower than that of carboxylic acids of similar weight. It is because esters cannot form hydrogen bonds between them. However, they can form hydrogen bonds between their oxygen atoms and hydrogen atoms of water molecules. Therefore, esters are slightly soluble in water.

Furthermore, an ester has a fruity smell, which is different from the corresponding carboxylic acid (acids usually have an unpleasant smell). In fact, these esters are the reason for the odour of many fruits; for example, pineapple gets its odour from ethyl ethanoate. And, this phenomenon has led to the use of esters in the food industry.

However, esters we use in a particular product to get a desired fruity smell is not the same compound that is present in the natural source. Nevertheless, esters can produce the same taste and odour. Moreover, although the compound is not the same as in the natural fruit, it is not dangerous to eat these food products since the structure of the ester is closely similar to that of the natural compound.

What is Ether

An ether is an organic compound which has an oxygen atom bound to two alkyl or aryl groups. We can name a simple ether as alkyl ethers because they contain two small alkyl groups attached to an oxygen atom. In its nomenclature, we need to list the alkyl groups in alphabetical order and add the term “ether” at the end. For example, if an ether has a methyl group and an n-butyl group bonded to the oxygen atom, we name it as “n-butylmethyl ether”.

Ethers can dissolve a wide range of polar and nonpolar compounds. It is mainly because ethers do not have a hydrogen bond network that has to be broken in order to dissolve a solute. Therefore, nonpolar compounds tend to dissolve in diethyl ether better than alcohols.

In the general structure of ether, the oxygen has an sp³ hybridization, and the two lone pairs are in two hybridized orbitals while two participate in bonding with R groups. R-O-R’ bond angle is about 104.5°, which is similar to water. Boiling points of ethers are roughly comparable with those of hydrocarbons with the same molecular weight, but the boiling points of ethers are less than the value of alcohols. Though ethers cannot make hydrogen bonds within them, they are able to form hydrogen bonds with other compounds such as water. Therefore, ethers are soluble in water, but the solubility may decrease depending on the length of the hydrocarbon chains attached.

What is the Difference Between Ester and Ether?

An ester is an organic compound formed by the reaction of an oxoacid with a hydroxyl compound. An ether, in contrast, is an organic compound which has an oxygen atom bound to two alkyl or aryl groups. The key difference between ester and ether is that the functional group of ester is –COO, whereas the functional group of ether is –O-. The general chemical formula of ester and ether are RC(=O)OR’ and R-O-R’, respectively. Moreover, another significant difference between ester and ether is that the ester has a carbonyl group in its functional group where ether doesn’t.

More importantly, esters have a fruity smell, while ether has a strong ethereal odour. Therefore, we can consider this also as a difference between ester and ether. Also, esters have lower boiling points than carboxylic acids and alcohols of the same weight while ether has boiling points lower than esters, carboxylic acids, and alcohols of the same weight.

Summary – Ester vs Ether

An ester is an organic compound that forms by reacting an oxoacid with a hydroxyl compound. An ether, on the other hand,  is an organic compound which has an oxygen atom bound to two alkyl or aryl groups. The key difference between ester and ether is that the functional group of ester is –COO, whereas the functional group of ether is –O-.

Reference:

1. DeRosa, Thomas F. Advances in Synthetic Organic Chemistry and Methods Reported in US Patents. Elsevier, 2006.
2. Ouellette, Robert J., and J. David Rawn. Organic Chemistry: Structure, Mechanism, and Synthesis. Elsevier, 2014.

Image Courtesy:

1. “Ester-general” By Sakurambo~commonswiki assumed. Own work assumed (based on copyright claims)., Public Domain) via Commons Wikimedia
2. “Ether-(general)” By Benjah-bmm27 assumed. Own work assumed (based on copyright claims) (Public Domain) via Commons Wikimedia