Key difference - aldehydes vs. ketone

Both aldehydes and ketones are carbon-containing chemical compounds that contain a carbonyl group. A carbonyl group contains a carbon atom that is doubly bonded to an oxygen atom (C = O). The main difference between aldehyde and ketone is their chemical structure; although both aldehydes and ketones share a carbonyl center within their chemical structure, their chemical arrangement of the surrounding atoms is different. While the carbonyl group of an aldehyde is bonded on one side to an alkyl group and on the other side to an H atom, the carbonyl group of the ketone is bonded to two alkyl groups (can be the same or different) on both sides.

This article examines

1. What is aldehyde? - Structure, naming, properties, tests

2. What is ketone? - Structure, naming, properties

3. What is the difference between aldehyde and ketone?

What is aldehyde?

As mentioned above, the chemical structure of an aldehyde can be defined as R-CHO, where the carbon atom is doubly bonded to the oxygen (R- (C = O) -H). Since one end of an aldehyde is always an H atom, aldehyde groups are only found at the end of a carbon chain. So if a carbonyl group is found at the end of a carbon chain, it is definitely an aldehyde. Aldehydes are extremely useful chemical compounds in industry. ie formaldehyde and acetaldehyde

Aldehydes are more reactive compared to ketones. It can be reduced to alcohols and also further oxidized until carboxylic acids are formed. Numerous other reactions follow, depending on the type of carbon chain to which the aldehyde is attached. When naming aldehydes according to the IUPAC system, it ends with a suffix "al". Therefore names like propanal, butanal, hexanal etc. are the aldehydes of the respective alkyl groups. An aldehyde can be differentiated from a ketone by several laboratory tests. The Schiff test, Tollen test and Fehling test are among the most popular tests. In the Fehling test, for example, the aldehydes form a red precipitate, while ketones show no reaction.

What is ketone?

The chemical structure of ketones is characterized by the R-CO-R 'form, in which the carbon atom is double bonded to the oxygen atom. Since the carbonyl bond is surrounded by alkyl groups on both sides, a ketone is never found at the end of a carbon chain.

Ketones are not as reactive as aldehydes. However, they are widely used as industrial solvents. ie acetone. Ketones are in their highest oxidation form and can therefore not be further oxidized. However, it is easily subject to reduction reactions with the formation of the corresponding alcohol. Ketones are easy to recognize by their IUPAC name, which ends with a suffix “one”. For example butanone, pentanone, hexanone, etc.

Difference between aldehyde and ketone

Chemical structure

Aldehydes are in the form of R-CHO.

Ketones are in the form of R-CO-R '.

Reactivity

Aldehydes are more reactive than ketones. Aldehydes are subject to oxidation with the formation of carboxylic acids.

Ketones cannot be oxidized without breaking the carbon chain.

IUPAC nomenclature

Aldehydes end with the suffix 'al'

Ketones end with the suffix "one".

Location of the carbonyl group

Aldehydes always occur at the end of a carbon chain.

Ketones always appear in the middle of the chain.

Natural occurrence

Aldehydes are usually found in volatile compounds like fragrances.

Ketones are often found in sugars and are commonly referred to as ketoses. However, there are aldehyde sugars called aldoses. (Read The Difference Between Aldose And Ketosis )

Image courtesy:

“Aldehyde_Structural_Formulae” by Jü - Own work (Public Domain) via Commons Wikimedia

"Ketone-general" By Benjah-bmm27 (based on copyright claims). Own work accepted (Public Domain) via Commons Wikimedia