''ortho''-Cresol (

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

name: 2-methylphenol, also known as 2-hydroxytoluene or ''ortho''-Toluenol) is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula CH₃C₆H₄(OH). It is a colourless solid that is widely used intermediate in the production of other chemicals. It is a derivative of

phenol Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire. The molecule consists of a phenyl group () ...

and is an isomer of ''p''-cresol and ''m''-cresol.Helmut Fiegein "Cresols and Xylenols" in Ullmann's Encyclopedia of Industrial Chemistry" 2007; Wiley-VCH, Weinheim.

Natural occurrences

''o''-Cresol is one of the chemical compounds found in

castoreum Castoreum is a yellowish exudate from the castor sacs of mature beavers used in combination with urine to territorial marking, scent mark their territory. Both beaver sexes have a pair of castor sacs and a pair of anal glands, located in two c ...

. This compound is gathered from the beaver's castor glands and found in the white cedar consumed by the

beaver Beavers (genus ''Castor'') are large, semiaquatic rodents of the Northern Hemisphere. There are two existing species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers are the second-large ...

. ''o''-Cresol is a constituent of

tobacco smoke Tobacco smoke is a sooty aerosol produced by the incomplete combustion of tobacco during the smoking of cigarettes and other tobacco products. Temperatures in burning cigarettes range from about 400 °C between puffs to about 900 °C ...

Production

Together with many other compounds, ''o''-cresol is traditionally extracted from

coal tar Coal tar is a thick dark liquid which is a by-product of the production of coke and coal gas from coal. It is a type of creosote. It has both medical and industrial uses. Medicinally it is a topical medication applied to skin to treat psoria ...

, the volatile materials obtained in the production of coke from

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...

. A similar source material is petroleum residues. These residue contains a few percent by weight of

and isomeric

cresol Cresols (also known as hydroxytoluene, toluenol, benzol or cresylic acid) are a group of aromatic organic compounds. They are widely-occurring phenols (sometimes called ''phenolics'') which may be either natural or manufactured. They are also c ...

s. In addition to the materials derived from these natural sources, about two thirds of the Western world's supply is produced by

methylation Methylation, in the chemistry, chemical sciences, is the addition of a methyl group on a substrate (chemistry), substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replac ...

of phenol using

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

. The

alkylation Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting al ...

is catalysed by metal oxides: :C₆H₅OH + CH₃OH → CH₃C₆H₄OH + H₂O Over-methylation gives

xylenol Xylenols are organic compounds with the formula (CH3)2C6H3OH. They are volatile colorless solids or oily liquids. They are derivatives of phenol with two methyl groups at various positions relative to the hydroxyl group. Six isomers exist, of whi ...

. Many other production methods have been examined, including oxidative decarboxylation of

salicylic acid Salicylic acid is an organic compound with the formula HOC6H4COOH. A colorless (or white), bitter-tasting solid, it is a precursor to and a active metabolite, metabolite of acetylsalicylic acid (aspirin). It is a plant hormone, and has been lis ...

, oxygenation of

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon with the chemical formula , often abbreviated as , where Ph stands for the phenyl group. It is a colorless, water Water is an inorganic compound with the c ...

, and hydrolysis of

2-chlorotoluene Chlorotoluenes are aryl chlorides based on toluene in which at least one aromatic hydrogen atom is replaced with a chlorine atom. They have the general formula C7H8–''n''Cl''n'', where ''n'' = 1–5 is the number of chlorine atoms. Monochlorotol ...

Applications

''o''-Cresol is mainly used as a precursor to other compounds. Chlorination and

etherification In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R′ re ...

gives members of commercially important

herbicide Herbicides (, ), also commonly known as weed killers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...

s, such as

2-methyl-4-chlorophenoxyacetic acid MCPA (2-methyl-4-chlorophenoxyacetic acid) is a widely used phenoxy herbicide introduced in 1945. It selectively controls broad-leaf weeds in pasture and Cereal, cereal crops. The mode of action of MCPA is as an auxin, which are growth hormones t ...

(MCPA). Nitration gives

dinitrocresol Dinitro-''ortho''-cresol (DNOC) is an organic compound with the structural formula CH3C6H2(NO2)2OH. It is a yellow solid that is only slightly soluble in water. It is extremely toxic to humans and was previously used as a herbicide and insectici ...

, a popular herbicide. Kolbe–Schmitt carboxylation gives ''o''-cresotinic acid, a pharmaceutical intermediate.

Carvacrol Carvacrol, or cymophenol, C6H3(CH3)(OH)C3H7, is a monoterpene, monoterpenoid phenol. It has a characteristic pungent, warm odor of oregano. Natural occurrence Carvacrol is present in the essential oil of ''Origanum vulgare'' (oregano), oil of t ...

, essence of oregano, is derived by alkylation of ''o''-cresol with

propene Propylene, also known as propene, is an unsaturated organic compound with the chemical formula . It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petroleum-like od ...

. The muscle relaxant

mephenesin Mephenesin (INN), also called myanesin, is a centrally acting muscle relaxant. It can be used as an antidote for strychnine poisoning. Mephenesin however presents with the major drawbacks of having a short duration of action and a much greater ef ...

is an ether derived from ''o''-cresol.

Health effects

Most exposures to cresols are at very low levels that are not harmful although, like phenols, cresols are skin irritants. When cresols are inhaled, ingested, or applied to the

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

at very high levels, they can be harmful. Breathing high levels of cresols for a short time results in irritation of the

nose A nose is a sensory organ and respiratory structure in vertebrates. It consists of a nasal cavity inside the head, and an external nose on the face. The external nose houses the nostrils, or nares, a pair of tubes providing airflow through the ...

and throat. Aside from these effects, very little is known about the effects of breathing cresols at lower levels over longer times. The acute LD₅₀ for oral ingestion by mice is 344 mg/kg.

References

External links

''o''-CRESOL (ICSC)

(accessed 22 December 2022)

{{DEFAULTSORT:Cresol, o- Alkylphenols Antiseptics Cresols