cresol, CH₃C₆H₄OH, any one of three aromatic alcohols present in coal tar. The three compounds are structural isomers; they may be thought of as hydroxy derivatives of toluene or as methyl derivatives of phenol. The names of the three compounds indicate which of the hydrogens on the benzene ring portion of the molecule have been replaced. Two adjacent hydrogens are replaced, one with a methyl group and one with a hydroxyl group, to form ortho-cresol, also called 2-hydroxytoluene, or 2-methylphenol. When a single unreplaced hydrogen lies between the two that are replaced, the compound formed is meta-cresol, 3-hydroxytoluene, or 3-methylphenol. When the replaced hydrogens lie opposite one another on the ring, the compound formed is para-cresol, 4-hydroxytoluene, or 4-methylphenol. Because the boiling points of these three compounds are nearly the same, a separation of a mixture of the three into its pure components is impractical. The mixture of cresols obtained from coal tar is called cresylic acid. The cresols are used in the manufacture of disinfectants and synthetic resins.

Cresols are organic compounds which are methylphenols. They are a widely occurring natural and manufactured group of aromatic organic compounds which are categorized as phenols (sometimes called phenolics). Depending on the temperature, cresols can be solid or liquid because they have melting points not far from room temperature. Like other types of phenols, they are slowly oxidized by long exposure to air and the impurities often give cresols a yellowish to brownish red tint. Cresols have an odor characteristic to that of other simple phenols, reminiscent to some of a "medicine" smell.

Chemical structure

In its chemical structure, a cresol molecule has a methyl group substituted onto the benzene ring of a phenol molecule. There are three forms of cresols that are only slightly different in their chemical structure: ortho-cresol (o-cresol), meta-cresol (m-cresol), and para-cresol (p-cresol). These forms occur separately or as a mixture.

Isomers of Cresol
Skeletal formula
Ball-and-stick model
General
Common name	o-cresol	m-cresol	p-cresol
Systematic name	2-methylphenol	3-methylphenol	4-methylphenol
Other names	ortho-cresol	meta-cresol	para-cresol
Molecular formula	C7H8O
SMILES	Oc1c(C)cccc1	Oc1cc(C)ccc1	Oc1ccc(C)cc1
Molar mass	108.14 g/mol
Appearance at room temperature and pressure	greasy-looking solid ready to melt on hot day	thicker liquid	greasy-looking solid
CAS number	[95-48-7]	[108-39-4]	[106-44-5]
	mixture of cresols: [1319-77-3]
Properties
Density and phase	1.05 g/cm3, solid	1.03 g/cm3, liquid	1.02 g/cm3, liquid
Solubility in pure water at 20-25°C	2.5 g/100 ml	2.4 g/100 ml	1.9 g/100 ml
soluble in strongly alkaline water
Melting point	29.8 °C (303.0 K)	11.8 °C (285.0 K)	35.5 °C (309.7 K)
Boiling point	191.0 °C (464.2 K)	202.0 °C (475.2 K)	201.9 °C (475.1 K)
Acidity (pKa)	10.26	10.99	10.26
Viscosity	solid at 25 °C	? cP at 25 °C	solid at 25 °C
Structure
Dipole moment	? D	? D	? D
Hazards
MSDS	External MSDS	?	?
Main hazards	flammable, ingestion and inhalation toxicity hazard
Flash point	81°C c.c.	86 °C	86 °C c.c.
R/S statement	R: 24/25-34 S: (1/2-)36/37/39-45
RTECS number	?	?	?
Supplementary data page
Structure & properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related phenols	phenol, xylenols
Related compounds	?
Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Chemical infobox

Applications

Cresols are used to dissolve other chemicals, as disinfectants and deodorizers, and to make specific chemicals that kill insect pests.

Cresol solutions are used as household cleaners and disinfectants, perhaps most famously under the trade name Lysol. In the past, cresol solutions have been used as antiseptics in surgery, but they have been largely displaced in this role by less toxic compounds. Lysol was also advertised as a disinfecting vaginal douche in mid-twentieth century America.

Cresols are found in many foods and in wood and tobacco smoke, crude oil, coal tar, and in brown mixtures such as creosote, cresolene and cresylic acids, which are wood preservatives. Small organisms in soil and water produce cresols when they break down materials in the environment.

Xylenols are dimethylphenols, or they can be thought of as methylcresols.

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.

Health effects

Most exposures to cresols are at very low levels that are not harmful. When cresols are breathed, ingested, or applied to the skin at very high levels, they can be very harmful. Effects observed in people include irritation and burning of skin, eyes, mouth, and throat; abdominal pain and vomiting; heart damage; anemia; liver and kidney damage; facial paralysis; coma; and death.

Breathing high levels of cresols for a short time results in irritation of the nose and throat. Aside from these effects, very little is known about the effects of breathing cresols, for example, at lower levels over longer times.

Ingesting high levels results in kidney problems, mouth and throat burns, abdominal pain, vomiting, and effects on the blood and nervous system.

Skin contact with high levels of cresols can burn the skin and damage the kidneys, liver, blood, brain, and lungs.

Short-term and long-term studies with animals have shown similar effects from exposure to cresols. No human or animal studies have shown harmful effects from cresols on the ability to have children.

It is not known what the effects are from long-term ingestion or skin contact with low levels of cresols.

References for Table of Properties

• o-CRESOL (ICSC)
• m-CRESOL (ICSC)
• p-CRESOL (ICSC)
• Environmental Science - SMILES Examples Notations

Footnotes

References

• (1983): Orchid floral fragrances and male euglossine bees: methods and advances in the last sesquidecade. Biol. Bull. 164: 355-395.