para-Cresol, also 4-methylphenol, is an organic compound 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 and is an isomer of o-cresol and m-cresol.[3]
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| Names | |
|---|---|
| Preferred IUPAC name 4-Methylphenol | |
| Systematic IUPAC name 4-Methylbenzenol | |
| Other names 4-Cresol p-Cresol 4-Hydroxytoluene p-Cresylic acid 1-Hydroxy-4-methylbenzene | |
| Identifiers | |
3D model (JSmol) | |
| 1305151 | |
| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| DrugBank | |
| ECHA InfoCard | 100.003.090 |
| EC Number |
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| 2779 | |
| KEGG | |
PubChem CID | |
| RTECS number |
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| UNII | |
CompTox Dashboard (EPA) | |
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| Properties | |
| C7H8O | |
| Molar mass | 108.13 |
| Appearance | colorless prismatic crystals |
| Density | 1.0347 g/ml |
| Melting point | 35.5 °C (95.9 °F; 308.6 K) |
| Boiling point | 201.8 °C (395.2 °F; 474.9 K) |
| 2.4 g/100 ml at 40 °C 5.3 g/100 ml at 100 °C | |
| Solubility in ethanol | miscible |
| Solubility in diethyl ether | miscible |
| Vapor pressure | 0.11 mmHg (25 °C)[1] |
| −72.1×10−6 cm3/mol | |
Refractive index (nD) | 1.5395 |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | May be fatal if swallowed, inhaled, or absorbed through skin. |
| GHS labelling: | |
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| Danger | |
| H201, H311, H314, H351, H370, H372, H373, H401, H412 | |
| P201, P202, P260, P264, P270, P273, P280, P281, P301+P310, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P307+P311, P308+P313, P310, P312, P314, P321, P322, P330, P361, P363, P405, P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | 86.1 °C (187.0 °F; 359.2 K) |
| Explosive limits | 1.1%–?[1] |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 207 mg/kg (oral, rat, 1969) 1800 mg/kg (oral, rat, 1944) 344 mg/kg (oral, mouse)[2] |
| NIOSH (US health exposure limits): | |
PEL (Permissible) | TWA 5 ppm (22 mg/m3) [skin][1] |
REL (Recommended) | TWA 2.3 ppm (10 mg/m3)[1] |
IDLH (Immediate danger) | 250 ppm[1] |
| Safety data sheet (SDS) | External MSDS |
| Related compounds | |
Related phenols | o-cresol, m-cresol, phenol |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
Production
Together with many other compounds, p-cresol is conventionally extracted from coal tar, the volatilized materials obtained in the roasting of coal to produce coke. This residue contains a few percent by weight of phenol and cresols. Industrially, p-cresol is currently prepared mainly by a two-step route beginning with the sulfonation of toluene:[4]
- CH3C6H5 + H2SO4 → CH3C6H4SO3H + H2O
Basic hydrolysis of the sulfonate salt gives the sodium salt of the cresol:
- CH3C6H4SO3H + 2 NaOH → CH3C6H4OH + Na2SO3 + H2O
Other methods for the production of p-cresol include chlorination of toluene followed by hydrolysis. In the cymene-cresol process, toluene is alkylated with propene to give p-cymene, which can be oxidatively dealkylated in a manner similar to the cumene process.[3]
Applications
p-Cresol is consumed mainly in the production of antioxidants, such as butylated hydroxytoluene (BHT). The monoalkylated derivatives undergo coupling to give an extensive family of diphenol antioxidants. These antioxidants are valued because they are relatively low in toxicity and nonstaining.[3][5][6]
Natural occurrences
In humans
p-Cresol is produced by bacterial fermentation of protein in the human large intestine. It is excreted in feces and urine,[7] and is a component of human sweat that attracts female mosquitoes.[8][9]
p-Cresol is a constituent of tobacco smoke.[10]
In other species
p-Cresol is a major component in pig odor.[11] Temporal glands secretion examination showed the presence of phenol and p-cresol during musth in male elephants.[12][13] It is one of the very few compounds to attract the orchid bee Euglossa cyanura and has been used to capture and study the species.[14] p-Cresol is a component found in horse urine during estrus that can elicit the Flehmen response.[15]