Difference Between Ethanoic Acid and Propanoic Acid

The key difference between ethanoic acid and propanoic acid is that the ethanoic acid molecule contains two carbon atoms, whereas the propanoic acid molecule contains three carbon atoms.

Ethanoic acid and propanoic acid are both carboxylic acids having the functional group –COOH. The terms ethanoic acid and propanoic acid are IUPAC names and acetic acid and propionic acid are the common names, respectively.

CONTENTS

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

What is Ethanoic Acid?

Ethanoic acid or acetic acid is an organic compound having the chemical formula CH3COOH. This compound is the second simplest carboxylic acid. It has a methyl group attached to a carboxylic acid. The systemic IUPAC name of acetic acid is ethanoic acid. Concerning the properties, the ethanoic acid exists as a colourless liquid having a pungent, vinegar-like odour. Also, this acid has a distinctive sour taste as well. Moreover, chemically, ethanoic acid 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.

Figure 01: Appearance of 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.

We can produce acetic acid industrially in synthetic routes or via biological routes. For example, we can produce acetic acid through the carbonylation of methanol, and we can produce this acid via fermentation of seeds such as apple cider, using potato mash, rice, etc.

What is Propanoic Acid?

Propanoic acid or propionic acid is the third simple carboxylic acid, having the chemical formula CH3CH2CO2H. This compound has three carbon atoms per propionic acid molecule. The molar mass of this compound is 74.079 g/mol. Propionic acid exists as a colourless, oily liquid at standard temperature. Further, this compound has a pungent, rancid odour. Propionic acid is miscible with water, and we can remove it from water by adding a salt.

Figure 02: Propanoic Acid

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 Ethanoic Acid and Propanoic Acid?

Ethanoic acid and propanoic acid are the IUPAC names for acetic acid and propionic acid, respectively. The key difference between ethanoic acid and propanoic acid is that the ethanoic acid molecule contains two carbon atoms, whereas the propanoic acid molecule contains three carbon atoms. The molar mass of ethanoic acid is 60.05 g/mol while the molar mass of propanoic acid is 74.079 g/mol. Moreover, ethanoic acid is a colourless liquid while propanoic acid is a colourless oily liquid.

The below infographic shows more differences between ethanoic acid and propanoic acid in tabular form.

Summary – Ethanoic Acid vs Propanoic Acid

Ethanoic acid and propionic acid are carboxylic acid compounds. The key difference between ethanoic acid and propanoic acid is that ethanoic acid molecule contains two carbon atoms, whereas propanoic acid molecule contains three carbon atoms.

Reference:

1. Helmenstine, Anne Marie. “Vinegar Chemical Formula.” ThoughtCo, Aug. 26, 2020, Available here.

Image Courtesy:

1. “Acetic acid” By W. Oelen – (CC BY-SA 3.0) via Commons Wikimedia
2. “Propionic acid” By MDaxo – Own work (CC BY-SA 4.0) via Commons Wikimedia

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