Phenol

Source: Wikipedia, the free encyclopedia.
Phenol
Names
Preferred IUPAC name
Phenol[1]
Systematic IUPAC name
Benzenol
Other names
  • Carbolic acid
  • Phenolic acid
  • Phenylic acid
  • Hydroxybenzene
  • Phenic acid
  • Phenyl alcohol
  • Phenyl hydroxide
Identifiers
3D model (
JSmol
)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard
100.003.303 Edit this at Wikidata
KEGG
RTECS number
  • SJ3325000
UNII
UN number 2821 (solution)
2312 (molten)
1671 (solid)
  • InChI=1S/C6H6O/c7-6-4-2-1-3-5-6/h1-5,7H checkY
    Key: ISWSIDIOOBJBQZ-UHFFFAOYSA-N checkY
  • InChI=1/C6H6O/c7-6-4-2-1-3-5-6/h1-5,7H
  • Oc1ccccc1
Properties
C6H6O
Molar mass 94.113 g/mol
Appearance Transparent crystalline solid
Odor Sweet and tarry
Density 1.07 g/cm3
Melting point 40.5 °C (104.9 °F; 313.6 K)
Boiling point 181.7 °C (359.1 °F; 454.8 K)
8.3 g/100 mL (20 °C)
log P 1.48[2]
Vapor pressure 0.4 mmHg (20 °C)[3]
Acidity (pKa)
  • 9.95 (in water),
  • 18.0 (in DMSO),
  • 29.1 (in acetonitrile)[4]
Conjugate base
Phenoxide
UV-vismax) 270.75 nm[5]
1.224 D
Pharmacology
C05BB05 (WHO) D08AE03 (WHO), N01BX03 (WHO), R02AA19 (WHO)
Hazards
GHS labelling:
GHS05: CorrosiveGHS06: ToxicGHS08: Health hazard[6]
Danger
H301, H311, H314, H331, H341, H373[6]
P261, P280, P301+P310, P305+P351+P338, P310[6]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
2
0
Flash point 79 °C (174 °F; 352 K)
Explosive limits
1.8–8.6%[3]
Lethal dose or concentration (LD, LC):
  • 317 mg/kg (rat, oral)
  • 270 mg/kg (mouse, oral)[7]
  • 420 mg/kg (rabbit, oral)
  • 500 mg/kg (dog, oral)
  • 80 mg/kg (cat, oral)[7]
  • 19 ppm (mammal)
  • 81 ppm (rat)
  • 69 ppm (mouse)[7]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 5 ppm (19 mg/m3) [skin][3]
REL (Recommended)
  • TWA 5 ppm (19 mg/m3)
  • C 15.6 ppm (60 mg/m3) [15-minute] [skin][3]
IDLH
(Immediate danger)
250 ppm[3]
Safety data sheet (SDS) [1]
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an

acidic, it requires careful handling because it can cause chemical burns.[5]

Phenol was first extracted from

Properties

Phenol is an organic compound appreciably soluble in water, with about 84.2 g dissolving in 1000 ml (0.895 M). Homogeneous mixtures of phenol and water at phenol to water mass ratios of ~2.6 and higher are possible. The sodium salt of phenol, sodium phenoxide, is far more water-soluble. It is a combustible solid (NFPA rating = 2). When heated, phenol produces flammable vapors that are explosive at concentrations of 3 to 10% in air. Carbon dioxide or dry chemical extinguishers should be used to fight phenol fires.[5]

Acidity

Phenol is a weak acid (pH 6.6). In aqueous solution in the pH range ca. 8 - 12 it is in equilibrium with the phenolate

anion C6H5O (also called phenoxide or carbolate):[10]

Resonance structures
of the phenoxide anion

Phenol is more acidic than aliphatic alcohols. Its enhanced acidity is attributed to

ortho and para carbon atoms through the pi system.[11] An alternative explanation involves the sigma framework, postulating that the dominant effect is the induction from the more electronegative sp2 hybridised 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 support of the second explanation, the pKa of the enol of acetone in water is 10.9, making it only slightly less acidic than phenol (pKa 10.0).[5]
Thus, the greater number of resonance structures available to phenoxide compared to acetone enolate seems to contribute little to its stabilization. However, the situation changes when solvation effects are excluded.

Hydrogen bonding

In

hydrogen bonds with a wide range of Lewis bases such as pyridine, diethyl ether, and diethyl sulfide. The enthalpies of adduct formation and the −OH IR frequency shifts accompanying adduct formation have been compiled.[12] Phenol is classified as a hard acid.[13][14]

Tautomerism

Phenol-cyclohexadienone tautomerism

Phenol exhibits

keto-enol tautomerism with its unstable keto tautomer cyclohexadienone, but the effect is nearly negligible. The equilibrium constant for enolisation is approximately 10−13, which means only one in every ten trillion molecules is in the keto form at any moment.[15] The small amount of stabilisation gained by exchanging a C=C bond for a C=O bond is more than offset by the large destabilisation resulting from the loss of aromaticity. Phenol therefore exists essentially entirely in the enol form.[16] 4, 4' Substituted cyclohexadienone can undergo a dienone–phenol rearrangement in acid conditions and form stable 3,4‐disubstituted phenol.[17]

For substituted phenols, several factors can favor the keto tautomer: (a) additional hydroxy groups (see resorcinol) (b) annulation as in the formation of naphthols, and (c) deprotonation to give the phenolate.[18]

Phenoxides are enolates stabilised by aromaticity. Under normal circumstances, phenoxide is more reactive at the oxygen position, but the oxygen position is a "hard" nucleophile whereas the alpha-carbon positions tend to be "soft".[19]

Reactions

Neutral phenol substructure "shape". An image of a computed electrostatic surface of neutral phenol molecule, showing neutral regions in green, electronegative areas in orange-red, and the electropositive phenolic proton in blue.
Phenol water phase diagram: Certain combinations of phenol and water can make two solutions in one bottle.

Phenol is highly reactive toward

sulfonation
, and related processes.

Phenol is so strongly activated that bromination and chlorination lead readily to polysubstitution.

catalysts (e.g. certain zeolite). Cresols and cumyl phenols can be produced in that way.[21]

Aqueous solutions of phenol are weakly acidic and turn blue litmus slightly to red. Phenol is neutralized by sodium hydroxide forming sodium phenate or phenolate, but being weaker than carbonic acid, it cannot be neutralized by sodium bicarbonate or sodium carbonate to liberate carbon dioxide.

C6H5OH + NaOH → C6H5ONa + H2O

When a mixture of phenol and benzoyl chloride are shaken in presence of dilute sodium hydroxide solution, phenyl benzoate is formed. This is an example of the Schotten–Baumann reaction:

C6H5COCl + HOC6H5 → C6H5CO2C6H5 + HCl

Phenol is reduced to benzene when it is distilled with zinc dust or when its vapour is passed over granules of zinc at 400 °C:[22]

C6H5OH + Zn → C6H6 + ZnO

When phenol is treated with diazomethane in the presence of boron trifluoride (BF3), anisole is obtained as the main product and nitrogen gas as a byproduct.

C6H5OH + CH2N2 → C6H5OCH3 + N2

Phenol and its derivatives react with iron(III) chloride to give intensely colored solutions containing phenoxide complexes.

Production

Because of phenol's commercial importance, many methods have been developed for its production, but the cumene process is the dominant technology.

Cumene process

The Hock process leading to phenol via autoxidation of cumene.

Accounting for 95% of production (2003) is the

Hock rearrangement:[8] Compared to most other processes, the cumene process uses mild conditions and inexpensive raw materials. For the process to be economical, both phenol and the acetone by-product must be in demand.[23][24]
In 2010, worldwide demand for acetone was approximately 6.7 million tonnes, 83 percent of which was satisfied with acetone produced by the cumene process.

A route analogous to the cumene process begins with

oxidized to a hydroperoxide, akin to the production of cumene hydroperoxide. Via the Hock rearrangement, cyclohexylbenzene hydroperoxide cleaves to give phenol and cyclohexanone. Cyclohexanone is an important precursor to some nylons.[25]

Oxidation of benzene, toluene, cyclohexylbenzene

The direct oxidation of benzene (C6H6) to phenol is theoretically possible and of great interest, but it has not been commercialized:

C6H6 + O → C6H5OH

Nitrous oxide is a potentially "green" oxidant that is a more potent oxidant than O2. Routes for the generation of nitrous oxide however remain uncompetitive.[26][23][25]

An electrosynthesis employing alternating current gives phenol from benzene.[27]

The oxidation of

Dow Chemical
, involves copper-catalyzed reaction of molten sodium benzoate with air:

C6H5CH3 + 2 O2 → C6H5OH + CO2 + H2O

The reaction is proposed to proceed via formation of benzyoylsalicylate.[8]

Autoxidation of cyclohexylbenzene give the hydroperoxide. Decomposition of this hydroperoxide affords cyclohexanone and phenol.[8]

Older methods

Early methods relied on extraction of phenol from coal derivatives or the hydrolysis of benzene derivatives.

Hydrolysis of benzenesulfonic acid

The original commercial route was developed by

benzenesulfonic acid, proceeding by the reaction of hydroxide with sodium benzenesulfonate to give sodium phenoxide. Acidification of the latter gives phenol. The net conversion is:[28]

C6H5SO3H + 2 NaOH → C6H5OH + Na2SO3 + H2O

Hydrolysis of chlorobenzene

Chlorobenzene can be hydrolyzed to phenol using base (Dow process) or steam (Raschig–Hooker process):[24][25][29]

C6H5Cl + NaOH → C6H5OH + NaCl
C6H5Cl + H2O → C6H5OH + HCl

These methods suffer from the cost of the chlorobenzene and the need to dispose of the chloride by product.

Coal pyrolysis

Phenol is also a recoverable byproduct of coal pyrolysis.[29] In the Lummus process, the oxidation of toluene to benzoic acid is conducted separately.

Miscellaneous methods

Amine to phenol[30]

Phenyldiazonium salts hydrolyze to phenol. The method is of no commercial interest since the precursor is expensive.[30]

C6H5NH2 + HCl + NaNO2 → C6H5OH + N2 + H2O + NaCl

Salicylic acid decarboxylates to phenol.[31]

Uses

The major uses of phenol, consuming two thirds of its production, involve its conversion to precursors for plastics.

phenolic resins, a famous example of which is Bakelite. Partial hydrogenation of phenol gives cyclohexanone,[32] a precursor to nylon. Nonionic detergents are produced by alkylation of phenol to give the alkylphenols, e.g., nonylphenol, which are then subjected to ethoxylation.[8]

Phenol is also a versatile precursor to a large collection of drugs, most notably

pharmaceutical drugs. Phenol is a component in liquid–liquid phenol–chloroform extraction technique used in molecular biology for obtaining nucleic acids from tissues or cell culture samples. Depending on the pH of the solution either DNA or RNA
can be extracted.

Phenol is so inexpensive that it also attracts many small-scale uses. It is a component of industrial paint strippers used in the aviation industry for the removal of epoxy, polyurethane and other chemically resistant coatings.[33] Due to safety concerns, phenol is banned from use in cosmetic products in the European Union[34][35] and Canada.[36][37]

Medical

Phenol was widely used as an

matrixectomy
. The procedure was first described by Otto Boll in 1945. Since that time phenol has become the chemical of choice for chemical matrixectomies performed by podiatrists.

Concentrated liquid phenol can be used topically as a local anesthetic for

tympanotomy tube placement, as an alternative to general anesthesia or other local anesthetics. It also has hemostatic and antiseptic qualities that make it ideal for this use. Phenol spray, usually at 1.4% phenol as an active ingredient, is used medically to treat sore throat.[38] It is the active ingredient in some oral analgesics such as Chloraseptic spray, TCP and Carmex.[39]

History

Phenol was discovered in 1834 by

phenyl". In 1843, French chemist Charles Gerhardt coined the name "phénol".[43]

The antiseptic properties of phenol were used by Sir Joseph Lister in his pioneering technique of antiseptic surgery. Lister decided that the wounds had to be thoroughly cleaned. He then covered the wounds with a piece of rag or lint[44] covered in phenol. The skin irritation caused by continual exposure to phenol eventually led to the introduction of aseptic (germ-free) techniques in surgery. Lister's work was inspired by the works and experiments of his contemporary Louis Pasteur in sterilizing various biological media. He theorized that if germs could be killed or prevented, no infection would occur. Lister reasoned that a chemical could be used to destroy the micro-organisms that cause infection.[45]

Meanwhile, in Carlisle, England, officials were experimenting with sewage treatment using carbolic acid to reduce the smell of sewage cesspools. Having heard of these developments, and having previously experimented with other chemicals for antiseptic purposes without much success, Lister decided to try carbolic acid as a wound antiseptic. He had his first chance on August 12, 1865, when he received a patient: an eleven-year-old boy with a tibia bone fracture which pierced the skin of his lower leg. Ordinarily, amputation would be the only solution. However, Lister decided to try carbolic acid. After setting the bone and supporting the leg with splints, he soaked clean cotton towels in undiluted carbolic acid and applied them to the wound, covered with a layer of tin foil, leaving them for four days. When he checked the wound, Lister was pleasantly surprised to find no signs of infection, just redness near the edges of the wound from mild burning by the carbolic acid. Reapplying fresh bandages with diluted carbolic acid, the boy was able to walk home after about six weeks of treatment.[46]

By 16 March 1867, when the first results of Lister's work were published in the Lancet, he had treated a total of eleven patients using his new antiseptic method. Of those, only one had died, and that was through a complication that was nothing to do with Lister's wound-dressing technique. Now, for the first time, patients with compound fractures were likely to leave the hospital with all their limbs intact

— Richard Hollingham, Blood and Guts: A History of Surgery, p. 62[46]

Before antiseptic operations were introduced at the hospital, there were sixteen deaths in thirty-five surgical cases. Almost one in every two patients died. After antiseptic surgery was introduced in the summer of 1865, there were only six deaths in forty cases. The mortality rate had dropped from almost 50 per cent to around 15 per cent. It was a remarkable achievement

— Richard Hollingham, Blood and Guts: A History of Surgery, p. 63[47]

Phenol was the main ingredient of the "carbolic smoke ball," an ineffective device marketed in London in the 19th century as protection against influenza and other ailments, and the subject of the famous law case

Carlill v Carbolic Smoke Ball Company
.

Second World War

The toxic effect of phenol on the central nervous system causes sudden collapse and loss of consciousness in both humans and animals; a state of cramping precedes these symptoms because of the motor activity controlled by the central nervous system.

Auschwitz when he volunteered to die in place of a stranger. Approximately one gram is sufficient to cause death.[51]

Occurrences

Phenol is a normal metabolic product, excreted in quantities up to 40 mg/L in human urine.

4-methylphenol during musth.[52][53] It is also one of the chemical compounds found in castoreum. This compound is ingested from the plants the beaver eats.[54]

Phenol is a measurable component in the aroma and taste of the distinctive

ppm, but it can be over 160ppm in the malted barley used to produce whisky.[56] This amount is different from and presumably higher than the amount in the distillate.[55]

Biodegradation

4-hydroxybenzoate.[57] Rhodococcus phenolicus is a bacterium species able to degrade phenol as sole carbon source.[58]

Toxicity

Phenol and its vapors are corrosive to the eyes, the skin, and the respiratory tract.

Since phenol is absorbed through the skin relatively quickly, systemic poisoning can occur in addition to the local caustic burns.[48] Resorptive poisoning by a large quantity of phenol can occur even with only a small area of skin, rapidly leading to paralysis of the central nervous system and a severe drop in body temperature. The LD50 for oral toxicity is less than 500 mg/kg for dogs, rabbits, or mice; the minimum lethal human dose was cited as 140 mg/kg.[48] The Agency for Toxic Substances and Disease Registry (ATSDR), U.S. Department of Health and Human Services states the fatal dose for ingestion of phenol is from 1 to 32 g.[65]

chloroform (a commonly used mixture in molecular biology for DNA and RNA purification).[citation needed] Phenol is also a reproductive toxin causing increased risk of miscarriage and low birth weight indicating retarded development in utero.[5]

Phenols

The word phenol is also used to refer to any compound that contains a six-membered

hydroxyl group (-OH). Thus, phenols are a class of organic compounds
of which the phenol discussed in this article is the simplest member.

See also

References

  1. ISBN 978-0-85404-182-4. Only one name is retained, phenol, for C6H5-OH, both as a preferred name and for general nomenclature.{{cite book}}: CS1 maint: DOI inactive as of April 2024 (link
    )
  2. ^ "Phenol_msds".
  3. ^ a b c d e NIOSH Pocket Guide to Chemical Hazards. "#0493". National Institute for Occupational Safety and Health (NIOSH).
  4. PMID 18324831
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  5. ^ a b c d e f "Phenol". PubChem, US National Library of Medicine. 10 June 2023. Retrieved 12 June 2023.
  6. ^ a b c Sigma-Aldrich Co., Phenol. Retrieved on 2022-02-15.
  7. ^ a b c "Phenol". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  8. ^ .
  9. .
  10. ^ Drago, R S. Physical Methods For Chemists, (Saunders College Publishing 1992), ISBN 0-03-075176-4
  11. ^ Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 ISBN 978-0-470-74957-9
  12. doi:10.1021/ed054p612. The plots shown in this paper used older parameters. Improved E&C parameters are listed in ECW model
    .
  13. .
  14. .
  15. .
  16. .
  17. on 2011-06-05. Retrieved 2010-03-31.
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  19. .
  20. ^ Roscoe, Henry (1891). A treatise on chemistry, Volume 3, Part 3. London: Macmillan & Co. p. 23.
  21. ^ a b "Phenol -- The essential chemical industry online". 2017-01-11. Retrieved 2018-01-02.
  22. ^ a b "Direct Routes to Phenol". Archived from the original on 2007-04-09. Retrieved 2007-04-09.
  23. ^ a b c Plotkin, Jeffrey S. (2016-03-21). "What's New in Phenol Production?". American Chemical Society. Archived from the original on 2019-10-27. Retrieved 2018-01-02.
  24. .
  25. .
  26. ^ Wittcoff, H.A., Reuben, B.G. Industrial Organic Chemicals in Perspective. Part One: Raw Materials and Manufacture. Wiley-Interscience, New York. 1980.
  27. ^ a b Franck, H.-G., Stadelhofer, J.W. Industrial Aromatic Chemistry. Springer-Verlag, New York. 1988. pp. 148-155.
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  31. ^ "CH207 Aircraft paintstripper, phenolic, acid" (PDF). Callington. 14 October 2009. Archived from the original (PDF) on 23 September 2015. Retrieved 25 August 2015.
  32. ^ "Prohibited substances in cosmetic product (Annex II, #1175, Phenol) - European Commission". ec.europa.eu. Retrieved 2018-07-06.
  33. ^ "CosIng - Cosmetics - GROWTH - European Commission". ec.europa.eu. Retrieved 2018-07-06.
  34. ^ Canada, Health (2004-06-18). "Cosmetic Ingredient Hotlist - Canada.ca". www.canada.ca. Retrieved 2018-07-06.
  35. ^ Canada, Health (2004-06-18). "Cosmetic Ingredient Hotlist: Prohibited and Restricted Ingredients - Canada.ca". www.canada.ca. Retrieved 2018-07-06.
  36. ^ "Phenol spray". drugs.com.
  37. ^ "How Does Our Lip Balm Work". Carmex. Archived from the original on 18 February 2015. Retrieved 18 February 2015.
  38. ^ F. F. Runge (1834) "Ueber einige Produkte der Steinkohlendestillation" (On some products of coal distillation), Annalen der Physik und Chemie, 31: 65-78. On page 69 of volume 31, Runge names phenol "Karbolsäure" (coal-oil-acid, carbolic acid). Runge characterizes phenol in: F. F. Runge (1834) "Ueber einige Produkte der Steinkohlendestillation," Annalen der Physik und Chemie, 31: 308-328.
  39. ^ Auguste Laurent (1841) "Mémoire sur le phényle et ses dérivés" (Memoir on benzene and its derivatives), Annales de Chimie et de Physique, series 3, 3: 195-228. On page 198, Laurent names phenol "hydrate de phényle" and "l'acide phénique".
  40. ^ Auguste Laurent (1836) "Sur la chlorophénise et les acides chlorophénisique et chlorophénèsique," Annales de Chemie et de Physique, vol. 63, pp. 27–45, see p. 44: Je donne le nom de phène au radical fondamental des acides précédens (φαινω, j'éclaire), puisque la benzine se trouve dans le gaz de l'éclairage. (I give the name of "phène" (φαινω, I illuminate) to the fundamental radical of the preceding acid, because benzene is found in illuminating gas.)
  41. ^ Gerhardt, Charles (1843) "Recherches sur la salicine," Annales de Chimie et de Physique, series 3, 7: 215-229. Gerhardt coins the name "phénol" on page 221.
  42. ^ Lister, Joseph (1867). "Antiseptic Principle Of The Practice Of Surgery".
  43. .
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  47. ^ The Experiments by Peter Tyson. NOVA
  48. ^ The Nazi Doctors Archived 2017-10-22 at the Wayback Machine, Chapter 14, Killing with Syringes: Phenol Injections. By Dr. Robert Jay Lifton
  49. ^ "Killing through phenol injection". Auschwitz: Final Station Extermination. Linz, Austria: Johannes Kepler University. Archived from the original on 2006-11-12.
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  51. ^ Musth in elephants. Deepa Ananth, Zoo's print journal, 15(5), pages 259-262 (article)
  52. ^ The Beaver: Its Life and Impact. Dietland Muller-Schwarze, 2003, page 43 (book at google books)
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  54. ^ "Bruichladdich". Bruichladdich. BDCL. Archived from the original on 21 April 2016. Retrieved 8 August 2015.
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  60. ^ World Health Organization/International Labour Organization: International Chemical Safety Cards, http://www.inchem.org/documents/icsc/icsc/eics0070.htm
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  63. ^ "Medical Management Guidelines for Phenol (C6H6O)". Agency for Toxic Substances and Disease Registry. U.S. Department of Health and Human Services. October 21, 2014. Retrieved 8 August 2015.
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