Difference Between Ketone and Ester

Ketones and esters are two types of organic compounds that have similar functional groups, but their structures and properties are quite different. In this essay, we will explore the differences between ketones and esters, including their structures, physical properties, and chemical properties.

What is Ketone?

A ketone is a molecule in which a carbon atom is covalently bonded to an oxygen atom to make a carbonyl group and carbons are bonded to this carbonyl.

Properties − Ketones are molecules which do have high reactivity and can easily react with other substances. This is due to the very polar nature of the carbonyl group which in turn gives the molecule a partial positive charge. This means that other substances are often attracted to the molecule with which they then readily react. In fact, nucleophilic addition and oxidation and reduction reactions are common.

Formation − There are several ways that a ketone can be formed. Many alcohols and hydrocarbons can be oxidized to form ketones. Molecules called alkynes can be modified by hydration to form ketone molecules.

Occurrence in nature − Ketone bodies are formed in the human body when fats are metabolized when there is insufficient glucose to supply the energy of the body. In individuals who have poorly controlled diabetes when excessive fats are broken down, these ketones can accumulate and the person thus often has a fruity smelling breath as a result.

What is Ester?

An ester is a molecule which has a carbonyl group and is a molecule in which the hydroxyl has been replaced by a group that is known as an alkoxy (an oxygen atom and an alkyl group).

Properties − The esters are molecules that have polarity (in other words they have a charge), and therefore do readily react with other molecules. Many small esters are soluble in water but the extent of solubility decreases as the size of the molecule increases. Long chain esters are thus insoluble in water and form part of many lipid molecules. An ester is less acidic than a ketone because of the presence of the alkoxy group. It is also less reactive than is a ketone molecule.

Formation − Esters can be formed from alcohols, carboxylic acids and certain of the inorganic acids such as nitric acid or phosphoric acid. The process in which carboxylic acid reacts with water in the presence of some type of acid in the presence of heat to form an ester is known as esterification.

Occurrence in nature − Esters of fatty acids make up many of the different fats that occur in nature and are often found in fruits. Pineapples and bananas have esters which give the fruits a specific smell. The waxes of plants are also an example of an ester that is found in nature. Cholesterol esters taken in through the diet are used to form cholesterol in animals, including in humans.

Differences: Ketone and Ester

Structure − Ketones and esters both contain a carbonyl group (C=O) which is a double bond between a carbon atom and an oxygen atom. However, the difference lies in the other atoms that are attached to the carbonyl group.

In a ketone, the carbonyl group is located in the middle of the carbon chain, and the two other groups that are attached to it can be either alkyl or aryl groups. In contrast, in an ester, the carbonyl group is located at the end of the carbon chain, and one of the groups attached to it is an alkyl group, while the other is an alkoxy group (-OR).

Physical Properties − Ketones and esters have different physical properties due to their differences in molecular structure. Ketones are polar compounds because the carbonyl group is polar, and the two other groups attached to it are nonpolar. This polarity allows ketones to have a higher boiling point than nonpolar compounds with similar molecular weight. In addition, ketones have a characteristic fruity odor, which is responsible for the smell of many fruits and flowers.

On the other hand, esters are also polar compounds due to the carbonyl group, but they have a lower boiling point than ketones because the alkyl group in an ester is less polar than an aryl group in a ketone. Esters have a sweet, fruity odor and are often used in perfumes and flavorings.

Chemical Properties − Ketones and esters have different chemical properties due to their differences in structure. Ketones are reactive compounds and can undergo many types of chemical reactions, such as nucleophilic addition and oxidation. Ketones can be reduced to alcohols by using reducing agents such as sodium borohydride or lithium aluminum hydride. Ketones can also react with nucleophiles, such as amines or water, to form addition products.

Esters, on the other hand, are less reactive than ketones and can undergo fewer types of reactions. Esters can be hydrolyzed by using acids or bases to form a carboxylic acid and an alcohol.

The following table highlights the major differences between Ketone and Ester −

Conclusion

There are many examples of ketones including acetone, phenylethanone, and propanone. Ketones form the basis for the production of many useful products in industry. For example, they are often used to make various solvents such as acetone that is widely used as a nail polish remover due to its properties as an excellent solvent. Ketones can also be used to strip paints and lacquers and even to make explosives and are often used in the tanning industry.

Examples of important esters include acetylcholine and ascorbic acid (vitamin C). Ethyl acetate is an ester that helps give flavor to beer. Some esters are used to make PVC wire insulation since it makes the insulation flexible. Many tricarboxylic acid esters can be found in wine and help to gives wine a specific smell. Esters are used in the manufacture of many substances including Plexiglas and Mylar film. Different esters are used to make dyes, solvents and even gasoline additives.

Vineet Nanda

Updated on: 10-Apr-2023

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