O-cresol is an organic compound that is a combination of a functional methyl group and phenol. It is also known as ortho-cresol and 2-methylphenol. This compound does occur naturally, but is also artificially produced. O-cresol is an isomer of two other common forms, meta-cresol (m-cresol) and para-cresol (p-cresol). All three of these compounds are known as phenols or methylphenols.
These molecules are aromatic, which means that their structure is more stable than chemically expected when they are formed. This stability is attributed to the cyclical structure that the atoms take on, when o-cresol is created. The electrons around the structure are able to circle freely, which lends greater stability to the entire compound.
This compound has a melting point of 85.64° F (29.8° C), which means that it can easily be liquefied by small changes in temperature. If o-cresol is heated to a temperature above 177.8° F (81° C), it becomes gaseous and may create an explosive air-vapor mixture. It also oxidizes when exposed to air at room temperature, a characteristic that it shares with all phenols. Once o-cresol is oxidized, it takes on a yellow or red tint, as well as a characteristic smell. This odor has often been described as being generally medicinal.
The most common uses of o-cresol are as a household cleaner, disinfectant, and ingredient in chemical pesticides. A well-known commercial form of this compound is the product Lysol®. In addition to being a popular cleaning product in the United States, Lysol® was also sold as a feminine hygiene product in the early part of the 20th century. O-cresols are also used as deodorizers, and to dissolve other chemicals. These compounds were used as surgical antiseptics, but have been replaced with less toxic alternatives.
O-cresol is found naturally in food products, as well as in tobacco smoke and crude oil. The compound is naturally generated when microorganisms present in soil and water break down organic material. Ingestion of o-cresol at low levels is non-toxic, but in high doses may cause abdominal pain and vomiting.
Prolonged skin contact with any amount of cresol burns the skin, and may also damage the liver and kidneys. Inhalation of gaseous cresols causes burning of the eyes, mouth, and throat, and, in concentrated amounts, can result in facial paralysis, coma, or even death. The long-term of effects of low-level cresol exposure, such as in a work environment, are unknown.