Benzoic Acid Polarity
The study of the polarity of the benzoic acid demonstrates the unique nature of chemistry through considering the bonding, electrical charge, and configuration of the molecule. The structure of benzoic acid consists of a large, non-polar benzene ring attached to a small, polar carboxylic acid functional group (C6H5COOH). The intermolecular forces within a benzoic acid are London dispersion bonds, dipole-dipole bonds, and hydrogen bonds. Benzoic acid is characterized as a solid colorless, crystalline. It functions as an important precursor for the synthesis of many other organic substances but is not compatible with strong bases. Benzoic acid is a cheap substance and readily available making it a good choice for chemists to research in the lab and for undergraduate students to experiment with.
Benzoic Acid Uses
Benzoic acid is widely used as a food preservative and antifungal agent to prevent the growth of mold, yeast, and some bacteria. The efficacy of benzoic acid is dependent on the pH of the food since the molecule must be absorbed within the cell and cause the intracellular pH to drop below five. This causes the anaerobic fermentation of glucose. Within the human body, benzoic acid is conjugated to glycine in the liver and excreted as hippuric acid. In the health care field, benzoic acid is used to treat ailments such as athlete’s foot and ringworm and has even been used as a decongestant and antiseptic.
Benzoic acid is considered a slightly polar molecule because the carboxylic acid functional group has some polarity with the carbonyl group. This makes sense because all acids typically contain some degree of polarity. In chemical reactions, the large, non-polar benzene ring often causes benzoic acid to act as a non-polar molecule. In theory, benzoic acid should be able to dissolve in both polar and non-polar solvents but does not like either. Benzoic acid resists dissolving in water because the large, non-polar benzene ring prefers to be around other non-polar benzene rings than polar water molecules, despite the acidic attachment. Unusually, benzoic acid dissolves differently in hot and cold water. It has a higher solubility in hot water and a poor solubility in cold water. This unique characteristic makes benzoic acid optimal for purification in the lab setting.
The polarity of benzoic acid continues to be an interesting phenomenon for chemists since it often reacts in a different behavior than expected by the rules of bonding and attraction in the field of chemistry.