p-Cresol

p-Cresol

Names
IUPAC name 4-Methylphenol
Other names 4-Hydroxytoluene, p-Hydroxytoluene, p-Methylphenol, 4-Cresol, p-Cresylic acid, 1-Hydroxy-4-methylbenzene
Identifiers
CAS Number	106-44-5
3D model (Jmol)	Interactive image
ChEBI	CHEBI:17847
ChEMBL	ChEMBL16645
ChemSpider	13839082
DrugBank	DB01688
ECHA InfoCard	100.003.090
KEGG	C01468
RTECS number	GO6475000
UNII	1MXY2UM8NV
InChI InChI=1S/C7H8O/c1-6-2-4-7(8)5-3-6/h2-5,8H,1H3 Key: IWDCLRJOBJJRNH-UHFFFAOYSA-N InChI=1/C7H8O/c1-6-2-4-7(8)5-3-6/h2-5,8H,1H3 Key: IWDCLRJOBJJRNH-UHFFFAOYAN
SMILES Cc1ccc(O)cc1
Properties
Chemical formula	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)
Solubility in water	2.4 g/100 ml at 40 °C 5.3 g/100 ml at 100 °C
Solubility in ethanol	fully miscible
Solubility in diethyl ether	fully miscible
Vapor pressure	0.11 mmHg (25°C)[1]
Refractive index (nD)	1.5395
Hazards
Main hazards	May be fatal if swallowed, inhaled, or absorbed through skin.
Safety data sheet	External MSDS
R-phrases	R34 R24 R25
S-phrases	S36 S37 S39 S45
NFPA 704	1 3 0
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]
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 5 ppm (22 mg/m^3) [skin][1]
REL (Recommended)	TWA 2.3 ppm (10 mg/m^3)[1]
IDLH (Immediate danger)	250 ppm[1]
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).
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Infobox references

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, an isomer of o-cresol and m-cresol.^[3]

Production

Together with many other compounds, p-cresol is traditionally 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. p-Cresol is currently prepared industrially mainly by a two step route beginning with the sulfonation of toluene:

CH₃C₆H₅ + H₂SO₄ → CH₃C₆H₄SO₃H + H₂O

Base hydrolysis of the sulfonate salt gives the sodium salt of the cresol:

CH₃C₆H₄SO₃Na + 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, phenol is alkylated with propylene to give p-cymene, which can be oxidatively dealkylated.^[3]

Applications

p-Cresol is mainly consumed in the production of antioxidants, e.g., butylated hydroxytoluene (BHT). The monoalkylated derivatives undergo coupling to give extensive family of diphenol antioxidants. These antioxidants are valued because they are relatively low in toxicity and nonstaining.^[3]

Natural occurrences

In humans

p-Cresol is produced by bacterial fermentation of protein in the human large intestine. It is excreted in the feces and urine,^[4] and is a component of human sweat attractive to female mosquitoes.^[5][6]

In other species

p-Cresol is a major component in pig odor.^[7]

Temporal glands secretion examination showed the presence of phenol and p-cresol during musth in male elephants.^[8][9]

p-Cresol is one of the very few compounds to attract the orchid bee Euglossa cyanura and has been used to capture and study the species.^[10]

References

1. "NIOSH Pocket Guide to Chemical Hazards #0156". National Institute for Occupational Safety and Health (NIOSH).
2. "Cresol (o, m, p isomers)". Immediately Dangerous to Life and Health. National Institute for Occupational Safety and Health (NIOSH).
3. Fiege, Helmut (2000). "Cresols and Xylenols". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a08_025. ISBN 3-527-30673-0.
4. Hamer, H. M.; De Preter, V.; Windey, K.; Verbeke, K. (2011). "Functional analysis of colonic bacterial metabolism: relevant to health?". AJP: Gastrointestinal and Liver Physiology. 302 (1): G1–G9. doi:10.1152/ajpgi.00048.2011. ISSN 0193-1857.
5. Hallem, Elissa A.; Nicole Fox, A.; Zwiebel, Laurence J.; Carlson, John R. (2004). "Olfaction: Mosquito receptor for human-sweat odorant". Nature. 427 (6971): 212–3. Bibcode:2004Natur.427..212H. doi:10.1038/427212a. PMID 14724626.
6. Linley, John R. (1989). "Laboratory tests of the effects of p-cresol and 4-methylcyclohexanol on oviposition by three species of Toxorhynchites mosquitoes". Medical and Veterinary Entomology. 3 (4): 347–52. doi:10.1111/j.1365-2915.1989.tb00241.x. PMID 2577519.
7. http://www.sciam.com/article.cfm?id=why-study-pig-odor[]
8. Rasmussen, L.E.L; Perrin, Thomas E (1999). "Physiological Correlates of Musth: Lipid Metabolites and Chemical Composition of Exudates". Physiology & Behavior. 67 (4): 539–49. doi:10.1016/S0031-9384(99)00114-6. PMID 10549891.
9. Ananth, Deepa. "Musth in elephants" (PDF). Zoos' Print Journal. 15 (5): 259–62. doi:10.11609/jott.zpj.14.4.259-62.
10. Williams, Norris H.; Whitten, W. Mark (June 1983). "Orchid Floral Fragrances and Male Euglossine Bees: Methods and Advances in the Last Sesquidecade". Biological Bulletin. 164 (3): 355–95. doi:10.2307/1541248. JSTOR 1541248.