Difference Between Formic Acid and Acetic Acid

The key difference between formic acid and acetic acid is that formic acid (or methanoic acid, HCOOH) contains a carboxylic acid group attached to a hydrogen atom whereas acetic acid (or ethanoic acid, CH₃COOH) has a methyl group attached to a carboxylic acid.

Both formic acid and acetic acid are simple carboxylic acids. However, formic acid is the simplest carboxylic acid whereas acetic acid is the second simplest carboxylic acid. Both these compounds are acidic compounds.

CONTENTS

1. Overview and Key Difference
2. What is Formic Acid
3. What is Acetic Acid
4. Similarities Between Formic Acid and Acetic Acid
5. Side by Side Comparison – Formic Acid vs Acetic Acid in Tabular Form
6. Summary

What is Formic Acid?

Formic acid is the simplest carboxylic acid in which a carboxylic acid group is attached to a hydrogen atom. The chemical formula of it is HCOOH or CH₂O₂. The IUPAC name of this compound is methanoic acid. This compound occurs naturally in some ants.

Some chemical facts about formic acid are as follows:

• Chemical formula – CH₂O₂ / HCOOH
• Molar mass – 46.03 g/mol
• Physical state – liquid at room temperature
• Color – colorless
• Odor – pungent odor
• Melting point – 8.4°C
• Boiling point – 100.8°C
• Water solubility – miscible with water

Vapor phase of formic acid has dimers due to the hydrogen bonding between its molecules. Two formic acid molecules can form two hydrogen bonds with each other to form a dimer. Because of this ability to form hydrogen bonds with water molecules it is miscible with water .

Formic Acid Production

Formic acid production mainly uses methyl formate and formamide. Hydrolysis of methyl formate produces formic acid. Methyl formate is a result of the reaction between methanol and carbon dioxide in the presence of a strong base such as sodium methoxide. Sometimes, methyl formate first converts into formamide (by reacting methyl formate with ammonia), which then hydrolyzes with sulfuric acid to yield formic acid.

What is Acetic Acid?

Acetic acid is the second simplest carboxylic acid which has a methyl group attached to a carboxylic acid group. The IUPAC name of this compound is ethanoic acid. The chemical formula of the acetic acid is CH₃COOH. Some chemical facts about acetic acid are as follows:

• Chemical formula – CH₃COOH
• Molar mass – 60.05 g/mol
• Physical state – liquid at room temperature
• Color – colorless
• Odor – vinegar-like odor
• Melting point – 16.6 °C
• Boiling point – 118.1 °C
• Water solubility – miscible with water

Acetic acid is a major constituent of vinegar. It has a characteristic sour taste and a pungent smell. The hydrogen atom of the carboxylic acid group of acetic acid can separate from the molecule via ionization of the molecule. Therefore, it is an acidic molecule. It is also a weak monoprotic compound. Solid acetic acid has the molecules arranged in a chain-like structure due to the hydrogen bonds present between the molecules. But is has dimers in its vapor phase.

Acetic Acid Production

There are two pathways to produce acetic acid: synthetic production and bacterial fermentation. The process utilized in the synthesis is mainly methanol carbonylation. This method involves the reaction between methanol and carbon monoxide.

What are the Similarities Between Formic Acid and Acetic Acid?

• Formic acid and acetic acid are carboxylic acids
• Both are colorless liquids at room temperature
• Both acids have a strong odor
• They both are capable of forming dimers
• With water molecules, both can form hydrogen bonds
• Further, the two acids are miscible with water

What is the Difference Between Formic Acid and Acetic Acid?

Summary – Formic Acid vs Acetic Acid

Formic acid and acetic acid are the simplest carboxylic acid compounds. The key difference between formic acid and acetic acid is that the formic acid contains a carboxylic acid group attached to a hydrogen atom whereas acetic acid has a methyl group attached to a carboxylic acid.

Reference:

1. “Formic Acid.” Wikipedia, Wikimedia Foundation, 14 Apr. 2018, Available here.
2. “Formic Acid.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
3. “Acetic Acid.” Wikipedia, Wikimedia Foundation, 24 Apr. 2018, Available here.