Difference Between Benzaldehyde and Acetaldehyde

Main Difference –  Benzaldehyde vs Acetaldehyde

Aldehydes are compounds composed of C, H and O atoms. There, essentially a carbonyl group is present in each and every aldehyde molecule. The functional group of aldehydes is the carbonyl group located at a terminal of the molecule. The general formula for aldehydes can be given as R-CHO. Aldehydes can be found as aliphatic compounds and aromatic compounds. Benzaldehyde and acetaldehyde are two examples of the group of aldehydes. Benzaldehyde is an aromatic compound whereas acetaldehyde is an aliphatic compound. This is the main difference between Benzaldehyde and Acetaldehyde.

Key Areas Covered

1. What is Benzaldehyde
      – Definition, Properties, and Uses
2. What is Acetaldehyde
      – Definition, Properties, and Uses
3. What is the Difference Between Benzaldehyde and Acetaldehyde
      – Comparison of Key Differences

Key Terms: Acetaldehyde, Aldehydes, Benzaldehyde, Benzene, Carbonyl Group

What is Benzaldehyde

Benzaldehyde is an organic compound that is composed of a benzene ring bonded to an aldehyde functional group. It is categorized as an aromatic aldehyde due to the presence of benzene ring. The molecular formula of benzaldehyde is C₆H₅CHO. The molar mass of benzaldehyde is about 106.12 g/mol.

Figure 1: Chemical Structure of Benzaldehyde

At room temperature and pressure, benzaldehyde is a colorless liquid with an almond-like odor. The boiling point of this liquid is about 178^oC. Benzaldehyde is denser than water. But it is insoluble in water. This is because benzaldehyde cannot form hydrogen bonds with water molecules. When benzaldehyde is added to water, it sinks to the bottom of the container. Benzaldehyde has a burning aromatic taste.

Benzaldehyde is used in manufacturing dyes, cinnamic acid, etc. It is also used in the production of perfumes and flavoring agents. Benzaldehyde is used in cosmetic productions as a denaturant, a flavoring agent, and as a fragrance.  Benzaldehyde is generally considered as a safe food additive. This is because it can be easily metabolized into benzoic acid and is not accumulated in our tissues.

What is Acetaldehyde

Acetaldehyde is an organic compound composed of a methyl group attached to an aldehyde functional group. The molecular formula of acetaldehyde is C₂H₄O. Sometimes it is written as CH₃CHO to show the groups present in the molecule. The molar mass of acetaldehyde is about 44.05 g/mol.

Figure 2: The Chemical Structure of Acetaldehyde

At room temperature and pressure, acetaldehyde is a colorless liquid with a pungent odor. It is a flammable liquid. The boiling point of this liquid is about 20.2^oC. Acetaldehyde is miscible with water. That is because aldehyde group can form hydrogen bonds with water molecules. The density of acetaldehyde is less than that of water.

Acetaldehyde is used in the production of acetic acid, perfumes, and flavors. Apart from that, it is used in the production of organic compounds such as 1-butanol, aniline dyes, synthetic rubber, plastics, etc. The most prominent process used for the manufacturing of acetaldehyde is Wacker process. It involves the oxidation of ethylene using a homogeneous palladium/copper system.

Difference Between Benzaldehyde and Acetaldehyde

Definition

Benzaldehyde: Benzaldehyde is an organic compound that is composed of a benzene ring bonded to an aldehyde functional group.

Acetaldehyde: Acetaldehyde is an organic compound composed of a methyl group attached to an aldehyde functional group.

Category

Benzaldehyde: Benzaldehyde is an aromatic aldehyde.

Acetaldehyde: Acetaldehyde is an aliphatic aldehyde.

Appearance and Odor

Benzaldehyde: Benzaldehyde is a colorless liquid with an almond-like odor.

Acetaldehyde: Acetaldehyde is a colorless liquid with a pungent odor.

Relative Density

Benzaldehyde: Benzaldehyde is denser than water.

Acetaldehyde: Acetaldehyde is less dense than water.

Boiling Point

Benzaldehyde: The boiling point of benzaldehyde is about 178^oC.

Acetaldehyde: The boiling point of acetaldehyde is about 20.2^oC.

Solubility

Benzaldehyde: Benzaldehyde is not soluble in water.

Acetaldehyde: Acetaldehyde is miscible with water.

Conclusion

Both benzaldehyde and acetaldehyde are two types of aldehyde compounds. They are used in cosmetic industry for the production of perfumes and other products due to their strong odor and other chemical properties. The main difference between benzaldehyde and acetaldehyde is that benzaldehyde is an aromatic compound whereas acetaldehyde aliphatic compound.

References:

1. “Benzaldehyde.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
2. Brown, William H. “Acetaldehyde (CH3CHO).” Encyclopædia Britannica, Encyclopædia Britannica, inc., 20 Oct. 2014, Available here.
3. “Acetaldehyde.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.

Image Courtesy:

1. “Benzaldehyde” By Calvero. – Selfmade with ChemDraw. (Public Domain) via Commons Wikimedia
2. “Acetaldehyde-2D-flat” By UAwiki – Own work (CC BY-SA 3.0) via Commons Wikimedia