The key difference between benzoic acid and sodium benzoate is that benzoic acid is the simplest aromatic carboxylic acid whereas sodium benzoate is the sodium salt of benzoic acid.
Benzoic acid is an aromatic carboxylic acid and sodium benzoate is a derivative of this benzoic acid. Both these are organic compounds because both these compounds have the aromatic benzene ring, substituted with a carbonyl group.
CONTENTS
1. Overview and Key Difference
2. What is Benzoic Acid
3. What is Sodium Benzoate
4. Side by Side Comparison – Benzoic Acid vs Sodium Benzoate in Tabular Form
5. Summary
What is Benzoic Acid
Benzoic acid is the simplest aromatic carboxylic acid. The molecular formula of benzoic acid is C6H5COOH. The molar mass of benzoic acid is about 122.12 g/mol. One benzoic acid molecule is composed of a benzene ring substituted with a carboxylic acid group (-COOH).
Figure 01: Benzoic Acid Crystals
At room temperature and pressure, benzoic acid is a white crystalline solid. It is slightly soluble in water. Benzoic acid has a pleasant odour. The melting point of benzoic acid solid is about 122.41 °C. The boiling point of benzoic acid is given as 249.2 °C, but at 370 °C, it decomposes.
Benzoic acid can undergo electrophilic aromatic substitution due to the electron-withdrawing property of the carboxylic group. Carboxylic acid can provide the aromatic ring with pi electrons. Then it becomes rich in electrons. Therefore, electrophiles can react with the aromatic ring.
Benzoic acid is a fungistatic compound that is widely used as a food preservative. This means it can prevent fungi growth in food. Benzoic acid can be naturally found in some fruits such as berries.
What is Sodium Benzoate?
Sodium benzoate is the sodium salt of benzoic acid having the chemical formula C6H5COONa. We can produce it via the neutralization reaction of benzoic acid. This production method involves the reaction between sodium hydroxide and benzoic acid. But, commercially, we can produce it also by partial oxidation of toluene in the presence of oxygen. Usually, sodium benzoate is present in many food products along with benzoic acid. Some rich sources are among vegetables and fruits. The major application of this compound is its use as a food preservative.
Figure 02: Sodium Benzoate
Sodium benzoate has the molar mass 144 g/mol. It appears as a white crystalline powder and it is odourless. The melting point of this compound is 410 °C.
What is the Difference Between Benzoic Acid and Sodium Benzoate?
The key difference between benzoic acid and sodium benzoate is that benzoic acid is the simplest aromatic carboxylic acid whereas sodium benzoate is the sodium salt of benzoic acid. However, both these are organic compounds because both these compounds have an aromatic benzene ring, substituted with a carbonyl group.
Moreover, benzoic acid is poorly water-soluble at room temperature, but if we heat the compound it becomes more water-soluble; however, sodium benzoate is water-soluble at room temperature. So, this is another difference between benzoic acid and sodium benzoate.
The melting point of benzoic acid solid is about 122.41 °C. But for sodium benzoate, the melting point is a very high value – 410 °C. Furthermore, both these compounds appear as white crystalline solids, but benzoic acid appears as needle-like structures while sodium benzoate is often a powdered solid. Both these compounds are important as food preservatives.
Summary – Benzoic Acid vs Sodium Benzoate
The key difference between benzoic acid and sodium benzoate is that benzoic acid is the simplest aromatic carboxylic acid whereas sodium benzoate is the sodium salt of benzoic acid. Both these are organic compounds because both these compounds have the aromatic benzene ring, substituted with a carbonyl group.
Reference:
1. “Sodium Benzoate.” Wikipedia, Wikimedia Foundation, 3 Nov. 2019, Available here.
2. Helmenstine, Anne Marie. “How to Make a Benzoic Acid Snow Globe.” ThoughtCo, Jul. 5, 2018, Available here.
Image Courtesy:
1. “Pile of benzoic acid crystals” By Devon Fyson – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Sodium benzoate-substance” By Chemik10 at Polish Wikipedia (CC BY-SA 3.0) via Commons Wikimedia