Chemical Method to Distinguish Acetic Acid from Formic Acid

The distinction between acetic acid and formic acid is a common problem in chemical analysis in chemical production and laboratories. Acetic acid and formic acid are both monocarboxylic acids, but there are significant differences in structure and properties. This paper will discuss how to distinguish acetic acid and formic acid by chemical methods from the aspects of physical and chemical properties analysis, chemical reaction methods and practical application.

1. physicochemical properties analysis

1. molecular structure The molecular formula of acetic acid is C₂ H₂ O₂, which is composed of an ethyl group and a carboxylic acid group, while the molecular formula of formic acid is HCOOCH3, which is composed of only a methyl group and a carboxylic acid group. This structural difference makes acetic acid more complex in physical properties.

2. Boiling Point The boiling point of acetic acid is 118.1°C, which is higher than that of formic acid at 17.2°C, which is mainly related to the longer carbon chain in its molecular structure. Acetic acid molecules have a larger molecular weight and stronger van der Waals forces, resulting in a significant increase in the boiling point.

3. Density Acetic acid has a density of 1.05g/cm³, which is higher than water, while formic acid has a density of 1.07g/cm³, which is slightly higher than acetic acid. This indicates that the solubility of formic acid in water is slightly higher than that of acetic acid.

4. Acid strength Acetic acid is more acidic than formic acid, which is related to the stability of its carboxylic acid group. The conjugation of the ethyl group in the acetic acid molecule increases its acidity.

2. chemical reaction method to distinguish

1. Reaction with carbonate When acetic acid reacts with carbonate, carbon dioxide gas is produced. The phenomenon is as follows: [\text{CH}3\text{COOH} \text{Na}2\text{CO}3 \rightarrow \text{CO}2\uparrow \text{Na}2\text{C}2\text{O}4 \text{H}2\text{O}] When formic acid reacts with carbonate, it also produces carbon dioxide gas: [\text{HCOOCH}3 \text{Na}2\text{CO}3 \rightarrow \text{CO}2\uparrow \text{Na}2\text{C}2\text{O}4 2\text{H}2\text{O}] However, due to the strong acidity of acetic acid, the reaction is faster.

2. Reaction of Acidic Potassium Permanganate Solution When acetic acid reacts with an acidic potassium permanganate solution, formic acid is oxidized to produce water and carbon dioxide gas: [\text{CH}3\text{COOH} \text{KMnO}4 \text{H}2\text{SO}4 \rightarrow \text{CO}_2\uparrow \text{CO}] Formic acid, on the other hand, does not react significantly with acidic potassium permanganate solution.

3. Esterification reaction with ethanol Acetic acid and ethanol can be esterified under acidic conditions to produce ethyl acetate and ethanol. The esterification reaction of formic acid and ethanol is relatively slow, and the products are different.

3. practical application

Chemical methods to distinguish between acetic acid and formic acid are of great significance in industrial production. For example, in the production of acetic acid, the production of acetic acid can be optimized by controlling the reaction conditions. In the field of environmental protection, the corresponding treatment scheme can be formulated by analyzing the properties of acidic substances.

Conclusion

By physicochemical property analysis and chemical reaction method, acetic acid and formic acid can be effectively distinguished. Acetic acid has a high boiling point, strong acidity and reacts with acidic potassium permanganate solution, while formic acid has a lower acidity and a slower esterification reaction with ethanol. These differences provide a scientific basis for practical application.