How to distinguish between propionic acid and acetic acid

In the chemical industry, propionic acid and acetic acid are common acidic substances, but they have significant differences in chemical properties, physical properties and practical applications. Differentiating between propionic acid and acetic acid is essential for selecting the right chemicals, process parameters and production process. How to distinguish these two acids will be analyzed in detail below from multiple perspectives.

1. Chemical formula and molecular structure

The chemical formula of acetic acid is CHYCOOH, and the molecular structure contains an ethyl group (CHYCOOH-) and a hydroxyl group (-OH), which is a dibasic acid. Its molecular weight is 60.05g/mol, is a weak acid, pH is usually around 2.8.

The chemical formula of propionic acid is CH₂ CH₂ COOH, and its molecular structure contains a propyl group (CH₂ CH₂ CO-) and a hydroxyl group (-OH), which is also a dibasic acid. Its molecular weight is 74.08g/mol, is a weak acid, pH is usually around 2.5.

Although both are dibasic acids, the difference in molecular formula and molecular weight can help us to distinguish between the two.

2. Acid strength difference

Both acetic acid and propionic acid are weak acids, but propionic acid is slightly more acidic than acetic acid. At the same concentration, the pH of propionic acid will be smaller (more acidic). For example, an acetic acid solution with a concentration of 01 M has a pH of about 2.8, while a propionic acid solution with the same concentration has a pH of about 2.5. Thus, by measuring the pH of the solution, it is possible to distinguish between propionic acid and acetic acid.

3. Density differences

Propionic acid and acetic acid have slightly different densities, and this difference can be distinguished by measuring the density of the solution. Acetic acid has a density of about 1.05g/cm³, while propionic acid has a density of about 1.07g/cm³. Therefore, in practical applications, it is possible to determine which acid is by measuring the density of the solution.

4. Appearance features

Propionic acid and acetic acid are somewhat similar in appearance, both are colorless and transparent liquids, but due to different molecular weights, the molecular weight of propionic acid is slightly larger, and may show more obvious signals on some instruments. The molecular structure of propionic acid also contains a double bond, which makes it show different activities in some reactions.

5. Industrial application

Acetic acid is mainly used in the production of acetic acid, acetic anhydride and other products, while propionic acid is used in the production of acrylic acid, propionic anhydride and other substances. The industrial applications of the two are different, and they can be distinguished by different application fields.

6. Detection method

If propionic acid and acetic acid cannot be distinguished by the above method, it can be confirmed by chemical detection methods. For example, the use of acidic strength test paper, or by mass spectrometry analysis and other means to distinguish.

Summary

Propionic acid and acetic acid can be effectively distinguished by chemical formula, acidity, density difference, appearance characteristics and industrial application. In actual operation, combining multiple methods can judge both more accurately. Understanding the difference between these two acids helps to select the right reagents and process parameters in chemical production, thereby improving production efficiency and product quality.

I hope this article can help you better understand and distinguish between propionic acid and acetic acid. If you need further experimental operation or process guidance, welcome to consult professional chemical experts.