o-Cresol

Chemical properties

colourless to light yellow liquid

Chemical properties

Cresol is a mixture of the three isomeric cresols, o-, m-, and p-cresol. Cresols are slightly soluble in water. m-Isomer: Colorless or yellow liquid with characteristic odor.

Chemical properties

o-Cresol has a musty, phenolic aftertaste.

Physical properties

Colorless solid or liquid with a phenolic odor; darkens on exposure to air. An odor threshold concentration of 0.28 ppb_v was reported by Nagata and Takeuchi (1990).

Occurrence

Reported in Acacial farnesiana, ylang-ylang oil (probably as p-cresyl acetate), jasmine absolute, orange oil from leaves, the essence from flowers of Lilium candidum, anise seed oil, the essence of Artemisia santolinoflia, and some sea algae. Also reported found in asparagus, peppermint oil, cheddar cheese, provolone cheese, butter, milk, lean fish, boiled egg, smoked pork, rum, Scotch whiskey, red wine, white wine, coffee and mango.Reported found in cinnamon, coffee, Oriental tobacco, rum, sherry, tea, tomato and whiskey.

The Uses of o-Cresol

o-Cresol is used as a disinfectant and solvent. Lysol disinfectant is a 50% (v/v) mixed-cresol isomer in a soap emulsion formed on mixing with water. Besides disinfection products at solutions of 1–5%, the cresols are used as degreasing compounds, paintbrush cleaners, and additives in lubricating oils. Cresols were previously widely used for disinfection of poultry houses, but this use was discontinued because of their toxicity; they cause respiratory problems and abdominal edema in young chicks. o-Cresol has been used in synthetic resins, explosives, petroleum, photographic, paint, and agricultural industries.

The Uses of o-Cresol

Disinfectant; phenolic resins; tricresyl phosphate; ore flotation; textile scouring agent; organic intermediate; manufacturing salicylaldehyde, coumarin, and herbicides; surfactant; synthetic food flavors (para isomer only); food antioxidant; dye, perfume, plastics, and resins manufacturing.

The Uses of o-Cresol

o-Cresol is used mostly as an intermediate for the production of pesticides, epoxy resins, dyes, and pharmaceuticals, but also as a component of disinfectants and cleaning agents. o-Cresol is readily biodegradable and has a low bioaccumulation or geoaccumulation potential. Antiseptics; disinfectants; solvent; insecticides; resins; flame-retardant plasticizers

Definition

ChEBI: A cresol that is phenol substituted by a methyl group at position 2. It is a minor urinary metabolite of toluene.

Production Methods

Approximately 60% of o-cresol is obtained from coal-tar and crude oil by using classical techniques such as distillation, stripping, and liquid–liquid extraction. The remaining 40% is obtained synthetically by the alkylation of phenol with methanol. The cresols (cresylic acids) are methyl phenols and generally appear as a mixture of isomers. o-Cresol is a 2-methyl derivative of phenol and is prepared from o-toluic acid or obtained from coal tar or petroleum. Crude cresol is obtained by distilling “gray phenic acid” at a temperature of ≈180–201°C. o-Cresol may be separated from the crude or purified mixture by repeated fractional distillation in vacuo. It can also be prepared synthetically by diazotization of the specific toluidine or by fusion of the corresponding toluenesulfonic acid with sodium hydroxide.

Aroma threshold values

Aroma characteristics at 1.0%: phenolic, medicinal, sweet spicy, smoky with a methyl salicylate nuance.

Taste threshold values

Taste characteristics at 2.0 ppm: sweet medicinal, phenolic and tarlike.

Synthesis Reference(s)

Tetrahedron Letters, 30, p. 5215, 1989 DOI: 10.1016/S0040-4039(01)93745-1
Chemical and Pharmaceutical Bulletin, 27, p. 816, 1979 DOI: 10.1248/cpb.27.816
Journal of the American Chemical Society, 107, p. 2571, 1985 DOI: 10.1021/ja00294a073

General Description

Colorless or yellow to brown-yellow or pinkish colored liquid with a phenol-like odor. Toxic by ingestion and/or skin absorption. May have a flash point between 100 and 199°F. Causes burns to skin, eyes and mucous membranes. Insoluble in water.

Air & Water Reactions

Sensitive to light and air. Insoluble in water.

Reactivity Profile

o-Cresol is incompatible with oxidizing agents and bases. Mixing o-Cresol with chlorosulfonic acid, nitric acid and oleum in a closed contained caused the temperature and pressure to increase.

Hazard

Questionable carcinogen.

Health Hazard

The chemical is rated as a very toxic compound with a probable oral lethal dose in humans of 50-500 mg/kg, or between 1 teaspoon and 1 ounce for a 70 kg (150 lb.) person. It is a strong dermal irritant and frequently causes dermatitis. Serious or fatal poisoning may result if large areas of skin are wet with cresol, o- and the substance is not removed immediately. Ingestion of even a small amount may cause paralysis and coma. It is corrosive to body tissues, with toxicity similar to phenol.

Fire Hazard

Fire may produce irritating or poisonous gases. Runoff from fire control water may give off poisonous gases. o-Cresol may burn but does not ignite readily. Container may explode in heat of fire. Slight explosion and fire hazard in the form of vapor when exposed to heat or flame. When heated to decomposition, o-Cresol emits highly toxic fumes. Reacts violently with nitric acid, oleum, and chlorosulfonic acid. Hazardous polymerization may not occur.

Flammability and Explosibility

Not classified

Safety Profile

Poison by ingestion, inhalation, subcutaneous, intravenous, and intraperitoneal routes. Moderately toxic by skin contact. A severe eye and skin irritant. Human mutation data reported. Questionable carcinogen with experimental neoplastigenic data. Flammable when exposed to heat, flame, or oxidants. To fight fire, water may be used to blanket fire; foam, fog, mist, dry chemical. See also other cresol entries and PHENOL.

Potential Exposure

Cresol is used as a disinfectant and fumigant; as an ore flotation agent, and as an intermediate in the manufacture of chemicals, dyes, plastics, and antioxidants. A mixture of isomers is generally used; the concentrations of the components are determined by the source of the cresol.

Source

Detected in distilled water-soluble fractions of 87 octane gasoline (6.61 mg/L), 94 octane gasoline (0.57 mg/L), Gasohol (1.17 mg/L), No. 2 fuel oil (2.64 mg/L), jet fuel A (0.72 mg/L), diesel fuel (1.36 mg/L), and military jet fuel JP-4 (1.51 mg/L) (Potter, 1996). o-Cresol was also detected in 82% of 65 gasoline (regular and premium) samples (62 from Switzerland, 3 from Boston, MA). At 25 °C, concentrations were from 1.1–99 mg/L in gasoline and 70–6,600 μg/L in water-soluble fractions. Average concentrations were 18 mg/L in gasoline and 1.2 mg/L in watersoluble fractions (Schmidt et al., 2002).
A high-temperature coal tar contained 2-methylphenol at an average concentration of 0.25 wt % (McNeil, 1983).
Occurs naturally in white sandlewood, sour cherries, peppermint leaves (1–10 ppb), tarragon, asparagus shoots, tea leaves, coffee beans, Japanese privet, tomatoes, licorice roots, and African palm oil (Duke, 1992).
Schauer et al. (2001) measured organic compound emission rates for volatile organic compounds, gas-phase semi-volatile organic compounds, and particle phase organic compounds from the residential (fireplace) combustion of pine, oak, and eucalyptus. The gas-phase emission rates of 2-methylphenol were 89.6 mg/kg of pine burned, 47.7 mg/kg of oak burned, and 37.8 mg/kg of eucalyptus burned. The particle-phase emission rates were 0.018 mg/kg of oak burned and 0.006 mg/kg of eucalyptus burned.

Environmental Fate

Biological. Bacterial degradation of 2-methylphenol may introduce a hydroxyl group producing 3-methylcatechol (Chapman, 1972). In phenol-acclimated activated sludge, metabolites identified include 3-methylcatechol, 4-methylresorcinol, methylhydroquinone, α-ketobutyric acid, dihydroxybenzaldehyde, and trihydroxytoluene (Masunaga et al., 1986).
Chloroperoxidase, a fungal enzyme isolated from Caldariomyces fumago, reacted with 2- methylphenol forming 2-methyl-4-chlorophenol (38% yield) and 2-methyl-6-chlorophenol (Wannstedt et al., 1990).
Heukelekian and Rand (1955) reported a 5-d BOD value of 1.70 g/g which is 67.5% of the ThOD value of 2.72 g/g. In activated sludge inoculum, 95.0% COD removal was achieved. The average rate of biodegradation was 54.0 mg COD/g?h (Pitter, 1976).
Soil. In laboratory microcosm experiments kept under aerobic conditions, half-lives of 5.1 and 1.6 d were reported for 2-methylphenol in an acidic clay soil (<1% organic matter) and slightly basic sandy loam soil (3.25% organic matter) (Loehr and Matthews, 1992).
Surface Water. In river water, the half-life of 2-methylphenol was 2 and 4 d at 20 and 4 °C, respectively (Ludzack and Ettinger, 1960).
Groundwater. Nielsen et al. (1996) studied the degradation of 2-methylphenol in a shallow, glaciofluvial, unconfined sandy aquifer in Jutland, Denmark. As part of the in situ microcosm study, a cylinder that was open at the bottom and screened at the top was installed through a cased borehole approximately 5 m below grade. Five liters of water was aerated with atmospheric air to ensure aerobic conditions were maintained. Groundwater was analyzed weekly for approximately 3 months to determine 2-methylphenol concentrations with time. The experimentally determined first-order biodegradation rate constant and corresponding half-life were 0.2/d and 3.5 d, respectively. Groundwater contaminated with phenol and other phenols degraded in a methanogenic aquifer to methane and carbon dioxide. These results could not be duplicated in the laboratory utilizing an anaerobic digester (Godsy et al., 1983).
Photolytic. Sunlight irradiation of 2-methylphenol and nitrogen oxides in air yielded the following gas-phase products: acetaldehyde, formaldehyde, pyruvic acid, peroxyacetyl nitrate, nitrocresols, and trace levels of nitric acid and methyl nitrate. Particulate phase products were also identified and these include 2-hydroxy-3-nitrotoluene, 2-hydroxy-5-nitrotoluene, 2-hydroxy-3,5- dinitrotoluene, and tentatively identified nitrocresol isomers (Grosjean, 1984). Absorbs UV light at a maximum wavelength of 270 nm (Dohnal and Fenclová, 1995).
Chemical/Physical. Ozonation of an aqueous solution containing 2-methylphenol (200 to 600 mg/L) yielded formic, acetic, propionic, glyoxylic, oxalic, and salicylic acids (Wang, 1990). In a different experiment, however, an aqueous solution containing 2-methylphenol (1 mM) reacted with ozone (11.7 mg/min) forming 2-methylmuconic acid and hydrogen peroxide as end products. The proposed pathway of degradation involved electrophilic aromatic substitution by the first ozone molecule followed by a 1,3-dipolar addition of the second ozone molecule to the cleaved ring (Beltran et al., 1990).

Shipping

UN2076 Cresols, liquid, Hazard class: 6.1; Labels: 6.1-Poisonous materials, 8-Corrosive material. UN3455 Cresols, solid, Hazard class: 6.1; Labels: 6.1- Poisonous materials, 8-Corrosive material.

Purification Methods

It can be freed from m-and p-isomers by repeated fractional distillation, It crystallises from *benzene by addition of pet ether. It has been fractionallly crystallised by partial freezing of its melt. The 3,5-dinitrobenzoate (prepared with 3,5-dinitrobenzoyl chloride in dry pyridine, and recrystallised from EtOH or aqueous Me2CO) has m 138o. [Beilstein 6 IV 1940.]

Incompatibilities

Vapors may form explosive mixture with air. Incompatible with strong acids; oxidizers, alkalies, aliphatic amines; amides, chlorosulfonic acid; oleum. Decomposes on heating, producing strong acids and bases, causing fire and explosion hazard. Liquid attacks some plastics and rubber. Attacks many metals.

Waste Disposal

Wastewaters may be subjected to biological treatment. Concentrations may be further reduced by ozone treatment. High concentration wastes may be destroyed in special waste incinerators.