PHENOL

'Phenol'
Phenol Ball-and-stick model of phenol Space-filling model of phenol Phenol's potential surface
Systematic name	Phenol
Other names	Carbolic Acid Benzenol Phenylic Acid Hydroxybenzene Phenic acid
Chemical formula	C6H5OH
SMILES	Oc1ccccc1
Molar mass	94.11 g/mol
Appearance	White Crystalline Solid
CAS number	[108-95-2]
Properties
Density	1.07 g/cm3
Solubility in water	8.3 g/100 ml (20 °C)
Saturated solution (20 °C)	88.19 M
Melting point	40.5 °C
Boiling point	181.7 °C
Acidity (p''K''a)	9.95
Structure
Molecular shape	planar
Dipole moment	? D
Hazards
MSDS	External MSDS
EU classification	Toxic ('T') Muta. Cat. 3 Corrosive ('C')
NFPA 704
R-phrases	, , ,
S-phrases	, , , , ,
Flash point	79 °C
Autoignition temperature	715 °C
RTECS number	SJ3325000
Supplementary data page
Structure and properties	''n'', εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related compounds	Benzenethiol

'Phenol', also known under an older name of 'carbolic acid', is a toxic, colourless crystalline solid with a sweet tarry odor. Its chemical formula is C₆H₅OH and its structure is that of a hydroxyl group (-OH) bonded to a phenyl ring; it is thus an aromatic compound.

Contents

Phenols

Properties

Production

Uses

Hydrothermal chemistry

See also

References

External links

Phenols

Main articles: phenols

The word ''phenol'' is also used to refer to any compound which contains a six-membered aromatic ring, bonded directly to a hydroxyl group (-OH). In effect, phenols are a class of organic compounds of which the phenol discussed in this article is the simplest member.

Properties

Phenol has a limited solubility in water (8.3 g/100 ml). It is slightly acidic: the phenol molecule has weak tendencies to lose the H⁺ ion from the hydroxyl group, resulting in the highly water-soluble 'phenoxide' anion C₆H₅O⁻. Compared to aliphatic alcohols, phenol shows much higher acidity; it even reacts with aqueous NaOH to lose H⁺, whereas aliphatic alcohols do not. One explanation for the increased acidity is resonance stabilization of the phenoxide anion by the aromatic ring. In this way, the negative charge on oxygen is shared by the ortho and para carbon atoms ^[1]. In another explanation, increased acidity is the result of orbital overlap between the oxygen's lone pairs and the aromatic system ^[2]. In a third, the dominant effect is the induction from the sp² hybridized carbons; the comparatively more powerful inductive withdrawal of electron density that is provided by the sp² system compared to an sp³ system allows for great stabilization of the oxyanion. In making this conclusion, one can examine the pK_a of the enol of acetone, which is 10.9 in comparison to phenol with a pK_a of 10.0. ^[3]

Production

Phenol can be made from the partial oxidation of benzene or benzoic acid, by the cumene process, or by the Raschig process. It can also be found as a product of coal oxidation.

Uses

Phenol has antiseptic properties, and was used by Sir Joseph Lister (1827-1912) in his pioneering technique of antiseptic surgery, though the skin irritation caused by continual exposure to phenol eventually led to the substitution of aseptic (germ-free) techniques in surgery. It is also the active ingredient in some oral anesthetics such as Chloraseptic spray. Phenol was also the main ingredient of the Carbolic Smoke Ball, a device sold in London designed to protect the user against influenza and other ailments. In the early part of the 20th century, it was used in the Battle Creek Sanitarium to discourage female masturbation.^[4]
It is also used in the production of drugs (it is the starting material in the industrial production of aspirin), weedkiller, and synthetic resins (Bakelite, one of the first synthetic resins to be manufactured, is a polymer of phenol with formaldehyde). Exposure of the skin to concentrated phenol solutions causes chemical burns which may be severe; in laboratories where it is used, it is usually recommended that polyethylene glycol solution is kept available for washing off splashes. Washing with large amounts of plain water (most labs have a safety shower or eye-wash) and removal of contaminated clothing are required, and immediate ER treatment for large splashes; particularly if the phenol is mixed with chloroform (a commonly used mixture in molecular biology for DNA purification). Notwithstanding the effects of concentrated solutions, it is also used in cosmetic surgery as an exfoliant, to remove layers of dead skin. It is also used in phenolization, a surgical procedure used to treat an ingrown nail, in which it is applied to the toe to prevent regrowth of nails.
Injections of phenol have occasionally been used as a means of rapid execution. In particular, phenol was used as a means of extermination by the Nazis during the Second World War. Phenol injections were given to thousands of people in concentration camps, especially at Auschwitz-Birkenau. Injections were administered either by medical doctors or by their assistants; such injections were originally given intravenously, more commonly in the arm, but injection directly into the heart, so as to induce nearly instant death, was later preferred . One of the most famous inmates at Auschwitz to be murdered by carbolic acid injection was St. Maximilian Kolbe, a Catholic priest who volunteered to undergo three weeks of starvation and dehydration in the place of another inmate and who was finally injected with carbolic acid so that the Nazis could make more room in their holding cells.^[5]
A use of phenol in molecular biology is the separation of genetic material (nucleic acids) (DNA & RNA) from proteins.

Hydrothermal chemistry

Under laboratory conditions mimicking hydrothermal circulation (water, 200°C, 1.9 GPa), phenol is found to form from sodium hydrogen carbonate and iron powder (1.8% chemical yield) ^[6]. This discovery made in 2007 may be relevant to the origin of life question as phenol is a fragment of the biomolecule tyrosine.

See also

★ Bamberger rearrangement

★ Phenols

References

External links

★ International Chemical Safety Card 0070

★ Phenol Material Safety Data Sheet

★ National Pollutant Inventory - Phenol Fact Sheet

★ NIOSH Pocket Guide to Chemical Hazards

★ IARC Monograph: "Phenol"

★ Arcane Radio Trivia outlines competing uses for Phenol circa 1915