Difference Between Aldehyde and Alcohol

The key difference between aldehyde and alcohol is that aldehyde contains –CHO functional group whereas alcohol contains –OH functional group.

Aldehydes and alcohols are organic compounds. They have different functional groups, as well as different chemical and physical properties. An aldehyde has a carbonyl carbon atom (a carbon atom attached to an oxygen atom through a double bond), but there are no carbonyl centres in alcohols. Both aldehydes and alcohols are very important in organic synthesis reactions, as precursors for other compounds such as ketones.

CONTENTS

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

What is Aldehyde?

Aldehydes are organic compounds containing the –CHO group as the functional group. Therefore, it has a carbonyl centre (-C=O). The general formula of an aldehyde is R-CHO, where the R group can be either aromatic or aliphatic. Hence, the R group determines the reactivity of this organic molecule. Moreover, aromatic aldehydes are less reactive than aliphatic aldehydes.

Aromatic have their –CHO group attached to an aromatic group. However, use this name when there is an aromatic group somewhere in the aldehyde. In addition to these, aromatic groups have a delocalized pi-electron cloud because of the conjugated pi bond system (alternating pattern of single bonds and double bonds).

Aliphatic aldehydes have no aromatic rings attached to the –CHO group. Furthermore, these molecules do not have any aromatic ring attached to the compound. Since there are no aromatic rings, these molecules have no resonance stabilization as well. Hence, these molecules have highly electrophilic –CHO groups, making the reactivity of the molecules very high.

What is Alcohol?

Alcohols are organic compounds containing one or more hydroxyl groups (-OH). These molecules are composed of C, H and O atoms. These atoms are arranged in alkyl groups and hydroxyl groups. The hydroxyl group is attached to one carbon atom of the alkyl group.

We can synthesize alcohols through different methods: E.g. Ziegler and oxo processes, hydration reactions, biological routes such as fermentation, etc. An alcohol can act as either the starting molecule or the intermediate for the synthesis of other organic compounds. Moreover, some beverages contain alcohols as a major or minor component. Sometimes alcohols can be used as solvents for purification of compounds out of impure mixtures.

There are three types of alcohol structures as primary, secondary and tertiary alcohols. Primary alcohols are composed of a hydroxyl group that is attached to a carbon atom of the alkyl group which is attached to only one alkyl group. Secondary alcohols, on the other hand, are composed of a carbon atom that is attached to a hydroxyl group and two other alkyl groups. Moreover, tertiary alcohols are composed of a carbon atom that is bonded to a hydroxyl group and with three alkyl groups.

What is the Difference Between Aldehyde and Alcohol?

Aldehydes and alcohols are organic compounds. They have different functional groups, resulting in different chemical and physical properties. The key difference between aldehyde and alcohol is that aldehyde contains –CHO functional group whereas alcohol contains –OH functional group. Also, another difference between aldehyde and alcohol is that there is a carbonyl carbon in an aldehyde, but there are no carbonyl centres in alcohol.

Moreover, we can produce an aldehyde via oxidative routes and such as alcohol oxidation, while we can produce alcohol in three major ways: Ziegler and oxo processes, hydration reactions, and biological routes such as fermentation.

Below is a summary of the difference between aldehyde and alcohol.

Summary – Aldehyde vs Alcohol

Aldehydes and alcohols are organic compounds. They have different functional groups, resulting in different chemical and physical properties. The key difference between aldehyde and alcohol is that aldehyde contains –CHO functional group, whereas alcohol contains –OH functional group.

Reference:

1. “Alcohol.” Wikipedia, Wikimedia Foundation, 16 Mar. 2020, Available here.

Image Courtesy:

1. “FunktionelleGruppen Aldehyde”  By MaChe (talk) – Own work (Public Domain) via Commons Wikimedia
2. “Alcohol-(general)-skeletal” By Benjah-bmm27 (talk · contribs) – Own work (Public Domain) via Commons Wikimedia