Cresol

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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 "coal tar" smell. The name creosol reflects their structure, being phenols, and their traditional source, creosote.

Structure and production[edit]

In its chemical structure, a molecule of cresol has a methyl group substituted onto the ring of phenol. There are three forms (isomers) of cresol: ortho-cresol (o-cresol), meta-cresol (m-cresol), and para-cresol (p-cresol). These forms occur separately or as a mixture, which can also be called cresol or more specifically, tricresol. About half of the world's supply of cresols are extracted from coal tar.[1] The rest is produced synthetically, by methylation of phenol or hydrolysis of chlorotoluenes.[2]

Isomers of Cresol[3][4][5]
Skeletal formula
Ortho-cresol-2D-skeletal.png
Meta-cresol-2D-skeletal.png
Para-cresol-vertical-2D-skeletal.png
Ball-and-stick modelOrtho-cresol-3D-balls.pngMeta-cresol-3D-balls.pngPara-cresol-3D-balls.png
General
Common nameo-cresolm-cresolp-cresol
Systematic name2-methylphenol3-methylphenol4-methylphenol
Other namesortho-cresolmeta-cresolpara-cresol
Molecular formulaC7H8O
SMILESOc1c(C)cccc1Oc1cc(C)ccc1Oc1ccc(C)cc1
Molar mass108.14 g/mol
Appearance at room
temperature and pressure
colorless crystalsthicker liquidgreasy-looking solid
CAS number[95-48-7][108-39-4][106-44-5]
mixture of cresols (tricresol): [1319-77-3]
Properties
Density and phase1.05 g/cm3, solid1.03 g/cm3, liquid1.02 g/cm3, liquid
Solubility in pure water
at 20−25 °C
2.5 g/100 ml2.4 g/100 ml1.9 g/100 ml
soluble in strongly alkaline water
Melting point29.8 °C (303.0 K)11.8 °C (285.0 K)35.5 °C (309.7 K)
Boiling point191.0 °C (464.2 K)202.0 °C (475.2 K)201.9 °C (475.1 K)
Acidity (pKa)10.2610.0910.26
Viscositysolid at 25 °C ? cP at 25 °Csolid at 25 °C
Structure
Dipole moment1.35 D1.61 D1.58 D
Hazards
MSDS
Main hazardsflammable, ingestion and inhalation toxicity hazard
Flash point81 °C c.c.86 °C86 °C c.c.
R/S statementR24/25-R34 ((S1/2)-)S36/37/S39-S45
RTECS number
Related compounds
Related phenolsxylenols
Related compoundsbromo cresol
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references

Applications[edit]

Cresols are precursors or synthetic intermediates to other compounds and materials, including plastics, pesticides, pharmaceuticals, and dyes.[2]

Commercial examples[edit]

Derivatives of p-cresol include:

Derivatives of o-cresol include:

Derivatives of m-cresol include:

Health effects[edit]

Most exposures to cresols are at very low levels that are not harmful. When cresols are inhaled, 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 reproduction.

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

The Occupational Safety and Health Administration has set a permissible exposure limit at 5 ppm (22 mg/m3) over an eight hour time-weighted average, while the National Institute for Occupational Safety and Health recommends a limit of 2.3 ppm (10 mg/m3).[6]

References[edit]