The key difference between acetic acid and propionic acid is that acetic acid is a carboxylic acid that contains two carbon atoms, whereas propionic acid is a carboxylic acid that contains three carbon atoms.
Acetic acid and propionic acid are simple carboxylic acids having two and three carbon atoms per molecule, respectively. They have different chemical and physical properties.
CONTENTS
1. Overview and Key Difference
2. What is Acetic Acid
3. What is Propionic Acid
4. Side by Side Comparison – Acetic Acid vs Propionic Acid in Tabular Form
5. Summary
What is Acetic Acid?
Acetic acid is the second simplest carboxylic acid having the chemical formula CH3COOH. It is a colourless liquid having a pungent, vinegar-like odour. It has a distinctive sour taste as well. This compound has a methyl group attached to a carboxylic acid. It is a weak acid because it dissociates partially in an aqueous solution. The molar mass of acetic acid is 60.05 g/mol. The conjugate base of this acid is acetate ion. Moreover, the systemic IUPAC name of acetic acid is ethanoic acid.
In its solid form, acetic acid form chains by interconnecting the molecules through hydrogen bonds. In its vapour phase, there are dimers of acetic acid. Furthermore, in its liquid state, it is a hydrophilic protic solvent. Moreover, at physiological pH conditions, this compound exists in a fully ionized form as acetate. We can produce acetic acid in both synthetic and bacterial fermentation routes. In addition to these, in the synthetic route, acetic acid is produced via methanol carbonylation.
What is Propionic Acid?
Propionic acid is the third simple carboxylic acid having the chemical formula CH3CH2CO2H. It has three carbon atoms per propionic acid molecule. Also, its molar mass is 74.079 g/mol. It occurs as a colourless, oily liquid at standard temperature. It also has a pungent, rancid odour. Moreover, this compound is miscible with water, and we can remove it from water by adding a salt.
In both liquid and vapour phases, propionic acid occurs as dimers. Furthermore, we can produce this acid in industrial-scale via hydrocarboxylation of ethylene in the presence of a catalyst. Most of the times, the catalyst we use is nickel carbonyl compounds.
What is the Difference Between Acetic Acid and Propionic Acid?
Acetic acid is the second simplest carboxylic acid, having the chemical formula CH3COOH, while Propionic acid is the third simple carboxylic acid, having the chemical formula CH3CH2CO2H. The key difference between acetic acid and propionic acid is that acetic acid is a carboxylic acid, containing two carbon atoms whereas propionic acid is a carboxylic acid, containing three carbon atoms.
Furthermore, another difference between acetic acid and propionic acid is their odour; acetic acid has a pungent, vinegar-like odour while propionic acid has a pungent, rancid odour. Moreover, in solid form, acetic acid form chains by interconnecting the molecules through hydrogen bonds, whereas in the vapour phase, it forms dimers and in its liquid state, it is a hydrophilic protic solvent. However, in both liquid and vapour phases, there are dimers of propionic acid.
Summary – Acetic Acid vs Propionic Acid
Acetic acid is the second simplest carboxylic acid, having the chemical formula CH3COOH, while Propionic acid is the third simple carboxylic acid having the chemical formula CH3CH2CO2H. The key difference between acetic acid and propionic acid is that acetic acid is a carboxylic acid, containing two carbon atoms, whereas propionic acid is a carboxylic acid, containing three carbon atoms.
Reference:
1. Plessi, M. “Vinegar.” Encyclopedia of Food Sciences and Nutrition, 2003, pp. 5996–6004., doi:10.1016/b0-12-227055-x/01251-7.
Image Courtesy:
1. “Acetic-acid-2D-skeletal” (Public Domain) via Commons Wikimedia
2. “Propionic acid chemical structure” By Хорев Сергей – Own work (Public Domain) via Commons Wikimedia