Difference Between Ketone and Ester

The key difference between ketone and ester is that ketone has a carbonyl functional group whereas ester has a carboxylic acid functional group.

Ketones and esters are organic compounds which differ from each other according to the functional group they contain. Also, a notable difference between ketone and ester is their smell. The smell of ketones is pungent while ester smell is a fruity smell. There are some other differences as well, which have been described in this article.

CONTENTS

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

What is Ketone?

Ketone is a group of organic compounds which has a carbonyl group connected with two alkyl or aryl groups. Therefore, the general chemical structure is RC(=O)R’. There, R and R’ are carbon-containing groups. Ketones and aldehydes are closely related organic compounds containing carbonyl groups, but ketone differs from an aldehyde since aldehyde contains one alkyl or aryl group and a hydrogen atom connected to the carbonyl group.

In the nomenclature of the ketone, the carbonyl group is given a number (we should number the ketone from the terminal which is closest to the carbonyl group). Thus, the ketone is named by changing the suffix of the parent alkane from –ane to –anone. For example, a ketone having three carbon atoms and a carbonyl group at the second carbon atom is named as 2-propanone.

When considering the carbon atom of the carbonyl group, it is sp² hybridized. Therefore, simple ketones have a trigonal planar geometry. Also, this compound is polar due to the presence of C=O bond. Moreover, ketones act as nucleophiles at oxygen atom (of carbonyl group) and act as electrophiles at carbon atom (of the carbonyl group). Furthermore, they can form hydrogen bonds with water molecules through the lone electron pairs on the oxygen atom.

Production of Ketone

In the production of ketones for industrial uses, we use the oxidation of hydrocarbons in the air. i.e. acetone production via air-oxidation of cumene. But, for specialized applications, we can use ketones via oxidation of secondary alcohols. Other than that, there are several methods including, germinal halide hydrolysis, hydration of alkynes, and, ozonolysis.

What is Ester?

An ester is an organic compound which has two alkyl or aryl groups attached to a carboxylic group. Therefore, the general formula of an ester is RCO₂R′. An ester forms when the hydrogen atom of a carboxylic acid is replaced with an alkyl or aryl group. We can obtain esters from either carboxylic acids or alcohols.

In the nomenclature of an ester, a compound gets its name according to the name of the parent compound (alcohol or carboxylic acid). In the name of ester, we use the suffix –oate. It has two words in its name, which gives the name of alkyl (or aryl) group attached to the oxygen atom of the carboxylic acid functional group followed by the name of alkyl group attached to the carbon atom of the functional group (with the –oate suffix). For example, methyl methanoate has two methyl groups attached to the functional group on either side.

When considering the properties of esters, esters are more polar than ethers but less polar than alcohols. Moreover, they can participate in hydrogen bonding; thus, they are slightly water soluble. They are more volatile than carboxylic acids of the same weight.

Esters are the components in fruits that are responsible for the fruity aroma. Fruits that have esters include apple, durian, pineapple, pears, strawberry, etc. Moreover, the fats in our body are triesters derived from glycerol and fatty acid. In addition, esters are important industrially for the production of acrylate esters, cellulose acetate, etc.

Production of Ester

We can produce esters using several methods, the most important method being esterification of carboxylic acids with alcohols. Here, we need to treat carboxylic acid with an alcohol in the presence of a dehydrating agent. Moreover, we can produce this compound via esterification of carboxylic acids with epoxides, alkylation of carboxylate salts, carbonylation, etc.

What is the Difference Between Ketone and Ester?

Ketone is a group of organic compounds which has a carbonyl group connected with two alkyl or aryl groups. An ester is an organic compound which has two alkyl or aryl groups attached to a carboxylic group. Hence, the key difference between ketone and ester is that ketone has a carbonyl functional group whereas ester has a carboxylic acid functional group.

Furthermore, the general formula of a ketone is RC(=O)R’ and for ester it is RCO2R′. When considering the polarity, esters are more polar than ketones, and they are more volatile as well. So, we can consider this too as a difference between ketone and ester. Moreover, their specific smell is an easily distinguishable difference between ketone and ester. Besides, the production of ketones can be done via oxidation of hydrocarbons in the air while the production of esters can be done via esterification of carboxylic acids with alcohol.

Below info-graphic provides more comparisons regarding the difference between ketone and ester.

Summary – Ketone vs Ester

Ketones and esters are organic compounds. They differ from each other according to the functional groups that they have. Hence, the key difference between ketone and ester is that ketone has a carbonyl functional group whereas ester has a carboxylic acid functional group.

Reference:

1. Helmenstine, Anne Marie, Ph.D. “What Is an Ester in Chemistry?” ThoughtCo, May. 9, 2019, Available here.

Image Courtesy:

1. “Ketone-group-2D-skeletal” By Ketone-group-2D-skeletal.png: *Ketone-displayed.png: Benjah-bmm27derivative work: Alberrosidus (talk)derivative work: Vladsinger (talk) – Ketone-group-2D-skeletal.png (Public Domain) via Commons Wikimedia
2. “Ester-general” By No machine-readable author provided. Sakurambo~commonswiki assumed (based on copyright claims). – No machine-readable source provided. Own work assumed (based on copyright claims) (Public Domain) via Commons Wikimedia