pKa: About 4.2. This means it can act as a proton donor (H⁺) to produce benzoate ions (C₆H₅COO⁻). The low pKa value makes it more acidic than many simple carboxylic acids.

Reaction with Bases

Neutralization Reaction: On reaction with strong bases, such as sodium hydroxide, benzoic acid produces benzoate salts

Esterification

Reaction with Alcohols: Benzoic acid may be treated with alcohols in the presence of acid catalysts to give esters .

Reduction

Benzyl alcohol can be prepared by the reduction of benzoic acid using a reducing agent, lithium aluminum hydride .

Halogenation

Reaction with Halogens: Benzoic acid undergoes reaction with halogens-Cl₂ or Br₂-under acidic conditions to form halogenated derivatives.

Decarboxylation

Loss of CO₂: Benzoic acid can decarboxylate via heating with a mixture of sodium hydroxide and calcium oxide, known as soda lime to give toluene

Thermal Decomposition

Benzoic acid can decompose at very high temperatures into carbon dioxide, water and other products.

Formation of Anhydrides

Formation of Acid Anhydride: Benzoic acid can self-heat to give benzoic anhydride

Application

Food Preservation: E 210 is an antimicrobial agent, used as a preservative, in acidic foods and drinks.

Pharmaceuticals: It acts as an intermediate for the production of many drugs. Its antimicrobial property is also utilized in topical drugs.

Chemical Synthesis: It is used in the production of benzoates, benzoyl peroxide, and other chemicals that are used in plastics, dyes, and resins.

Cosmetics and Personal Care: Cosmetic formulations use it due to its preservative and anti-bacterial properties.

Industrial Applications: It is employed for perfumes production, flavoring agents and as a solvent in various chemical reactions.

Laboratory Applications: It is used as a reagent in organic synthesis and standard in titration.

Safety and Handling

Toxicity: Rated non-toxic at low concentrations although completely safe for application in foods, still can irritate skin, eyes and respiratory tract at higher concentrations.

Environmental Impact: Biodegradable, and its salts (such as sodium benzoate) are toxic to aquatic life at higher concentrations.

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Benzoic Acid Formula

Molecular formula for Benzoic acid is C₇H₆O₂. While structural formula is C₆H₅COOH.

It contains a benzene ring attached with a carboxylic acid group.

Physical properties

Molecular Weight: 122.12 g/mol

Appearance: White crystalline solid or powder

Odor: Weak, pleasant aromatic odour

Melting Point: About 122 °C (252 °F)

Boiling Point: About 249 °C (480 °F)

Density: About 1.32 g/cm³ at 20 °C

Explanation: It is more dense than water, which is 1 g/cm³.

Solubility

In Water:

Very slightly soluble (about 0.29 g/100 mL at 25 °C)

It has increased solubility with temperature.

In Organic Solvents:

It is soluble in ethanol, methanol, acetone, ether, and benzene.

This organic solubility makes it useful for any number of chemical purposes.

pH In Solution:

Weakly Acidic with a pH typically below 7 The pKa of benzoic acid is approximately 4.2, meaning it can donate protons (H⁺) in solution.

Refractive Index

Value: ≈1.540 (pure liquid)

Useful: to identify and characterize the chemical compound in laboratory settings.

Other Properties

Hygroscopicity: Benzoic acid can absorb moisture from the air, where this could be an issue during its use and storage.

Thermal Stability: Normally stable, but sensitive to decomposition at very high temperatures especially in presence of strong oxidizers.

Chemical properties

Acidity Dissociation: Benzoic acid is a weak acid that partially dissociates in water