Methylbenzoic acid (3-methylbenzoic acid)

3-Methylbenzoic acid combines the structural features of toluene and benzoic acid. The molecules of the substance consist of a phenyl ring that has a carboxy group and a methyl group. Between the two carbon atoms to which these substituents are attached, there is another carbon atom within the ring structure of the compound. In addition to 3-methylbenzoic acid, there are two isomeric substances, 2-methylbenzoic acid and 4-methylbenzoic acid, in which the carboxyl group and the methyl radical are on adjacent carbon atoms and on opposite carbon atoms in the phenyl ring. Accordingly, 3-methylbenzoic acid is also referred to as meta-methylbenzoic acid or m-methylbenzoic acid.

The aromatic compound has two reactive sites due to the unsaturated character of the phenyl ring and the carboxy group. Among other things, it can thus enter into addition reactions and the esterification reactions typical of carboxylic acids.

Under normal conditions, 3-methylbenzoic acid exists as a white solid in the form of crystalline scales. The compound melts when heated to 110 °C and changes to the gaseous state at a temperature of 263 °C. The substance has a slightly aromatic odor reminiscent of honey. 3-Methylbenzoic acid is only slightly soluble in water. In contrast, the compound is readily soluble in organic solvents such as diethyl ether and ethanol.

When stored as intended, 3-methylbenzoic acid is a chemically stable compound. However, contact with strong oxidizing agents can lead to dangerous reactions with a violent course.

The substance is flammable but difficult to ignite. Due to a swirling of fine particles of the compound, easily flammable and explosive dust-air mixtures can form. When processing 3-methylbenzoic acid, care must be taken to ensure that there is sufficient distance to possible ignition sources such as open flames, mechanically generated sparks, hot surfaces and electrostatic discharges. Gases that are hazardous to health, such as carbon monoxide and carbon dioxide, are released when the substance is burned.

3-Methylbenzoic acid is a hazardous substance according to the GHS classification. The compound causes hardly any irritation when it comes into contact with the skin, but it can lead to severe reddening and severe irritation of the eyes. The affected eye should be rinsed thoroughly under running water and then examined by an ophthalmologist. Wetted parts of the body can be cleaned with water, soap and polyethylene glycol 400.

Inhalation of dust from the substance may cause severe respiratory irritation and asthma-like symptoms. If 3-methylbenzoic acid is taken orally and swallowed, redness and painful irritation of the mouth and of the mucous membranes of the esophagus and stomach are to be expected. Gastrointestinal symptoms such as nausea, vomiting and diarrhea can also occur. If the compound is absorbed into the metabolism in higher amounts, disorders of the central nervous system, paralysis and kidney damage can occur. If poisoning with 3-methylbenzoic acid is suspected, seek medical treatment immediately.

With regard to a possible hazard to water bodies, there is still no assessment for the substance. However, the escape of 3-methylbenzoic acid into the ground, water bodies or wastewater should be avoided. The compound is not subject to any special transport regulations.