PhenolFrom Wikipedia, the free encyclopedia

This article is about the molecule. For the class of chemicals containing a phenol group, see Phenols.

Phenol

IUPAC name [hide]

Phenol

Other names[hide]

Carbolic Acid, Benzenol, Phenylic Acid, Hydroxybenzene, Phenic acid

Identifiers

CAS number 108-95-2 

PubChem 996

ChemSpider 971 

UNII 339NCG44TV 

DrugBank DB03255

KEGG D06536 

ChEBI CHEBI:15882 

ChEMBL CHEMBL14060 

RTECS number SJ3325000

ATC code C05 BB05 ,D08 AE03 , N01 BX03 , R02 AA19

Jmol-3D images Image 1

SMILES

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InChI

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Properties

Molecular formula C6H6O

Molar mass 94.11 g mol−1

Appearance transparent crystalline solid

Density 1.07 g/cm3

Melting point40.5 °C, 314 K, 105 °F

Boiling point181.7 °C, 455 K, 359 °F

Solubility in water 8.3 g/100 mL (20 °C)

Acidity (pKa) 9.95 (in water),

29.1 (in acetonitrile)[2]

λmax 270.75 nm[1]

Dipole moment 1.7 D

Hazards

GHS pictograms [3]

GHS hazard statements H301, H311, H314, H331, H341, H373[3]

GHS precautionary

statements

P261, P280, P301+310, P305+351+338,P310[3]

EU classification Toxic (T)

Muta. Cat. 3

Corrosive (C)

R-phrases R23/R24/R25-R34-R48/R20/R21/R22-R68

S-phrases (S1/2)-S24/S25-S26-S28-S36/S37/S39-S45

NFPA 704

230

COR

Flash point 79 °C

Related compounds

Related compounds Benzenethiol

   (verify) (what is:  / ?)

Except where noted otherwise, data are given for materials in theirstandard

state (at 25   °C, 100   kPa)

Infobox references

Phenol, also known as carbolic acid and phenic acid, is an organic compound with the chemical

formula C6H5OH. It is a white crystalline solid  at room temperature. The molecule consists of a phenyl (-C6H5),

bonded to a hydroxyl (-OH) group. It is produced on a large scale (about 7 billion kg/year) as a precursor to

many materials and useful compounds.[4] It is only mildly acidic but requires careful handling due to its

propensity to cause burns.

Phenol was first extracted from coal tar, and its major uses involve its conversion to plastics or related

materials. Phenols are key for building polycarbonates, epoxies, Bakelite, nylon, detergents and a large

collection of drugs, herbicides and pharmaceuticals.

See also: Bisphenol A

Contents

  [hide] 

1   Properties

• 1.1   Acidity

• 1.1.1   Phenoxide anion

• 1.1.2   Tautomerism

• 1.2   Reactions

2   Production

3   Uses

• 3.1   Niche uses

4   History

• 4.1   Second World War

5   Occurrence

6   Biodegradation

7   Toxicity

8   Phenols

9   See also

10   References

11   External links

[edit]Properties

Phenol is appreciably soluble in water, with about 8.3 g dissolving in 100 mL (0.88 M). The sodium salt of

phenol, sodium phenoxide, is far more water soluble.

[edit]Acidity

It is slightly acidic: the phenol molecules have weak tendencies to lose the H+ ion from the hydroxyl group,

resulting in the highly water-soluble phenolate anion C6H5O− (also called phenoxide).[5] Compared

to aliphatic alcohols, phenol is about 1 million times more acidic, although it is still considered a weak acid. It

reacts completely with aqueous NaOH to lose H+, whereas most alcohols react only partially. Phenols are less

acidic than carboxylic acids, and even carbonic acid.

One explanation for the increased acidity over alcohols 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.[6] In

another explanation, increased acidity is the result of orbital overlap between the oxygen's lone pairs and the

aromatic system.[7] In a third, the dominant effect is the induction from the sp 2   hybridised carbons ; the

comparatively more powerful inductive withdrawal of electron density that is provided by the sp2 system

compared to an sp3system allows for great stabilization of the oxyanion.

In making this conclusion, one can examine the pKa of the enol of acetone, which is 19.0, in comparison to

phenol with a pKa of 10.0.[8]However, this similarity of acidities of phenol and acetone enol is not observed in

the gas phase, and is because the difference of solvation energies of the deprotonated acetone enol and

phenoxide almost exactly offsets the experimentally observed gas phase acidity difference. It has recently been

shown that only about 1/3 of the increased acidity of phenol is due to inductive effects, with resonance

accounting for the rest.[9]

[edit]Phenoxide anion

Phenol can be deprotonated with moderate base such as triethylamine, forming the nucleophilic phenoxide

anion or phenolate anion, which is highly water-soluble.

Resonance structures of the phenoxide anion

The phenoxide anion has a similar nucleophilicity to free amines, with the further advantage that its conjugate

acid (neutral phenol) does not become entirely deactivated as a nucleophileeven in moderately acidic

conditions. Phenols are sometimes used in peptide synthesis to "activate" carboxylic acids or esters to

form activated esters. Phenolate esters are far more stable than acid anhydrides or acyl halides but are

sufficiently reactive under mild conditions to facilitate the formation of amide bonds.

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".[10]

[edit]Tautomerism

Phenol-cyclohexadienone tautomerism

Phenol exhibits keto-enol tautomerism with its unstable keto tautomer cyclohexadienone, but only a tiny

fraction of phenol exists as the keto form. The equilibrium constant for enolisation is approximately 10−13,

meaning that only one in every ten trillion molecules is in the keto form at any moment.[11] 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 entirely in the enol form.[12]

[edit]Reactions

Neutral phenol substructure "shape". An image of a computed electrostatic surface of neutral phenol, showing neutral

regions in green, electronegative areas in orange-red, and the electropositive phenolic proton in blue.

Phenol is highly reactive toward electrophilic aromatic substitution as the oxygen atom's pi electrons donate

electron density into the ring. By this general approach, many groups can be appended to the ring,

via halogenation, acylation,sulfonation, and other processes. However, phenol's ring is so strongly activated -

second only to aniline - that bromination or chlorination of phenol leads to substitution on all carbons ortho and

para to the hydroxy group, not only on one carbon.

[edit]Production

Because of phenol's commercial importance, many methods have been developed for its production. The

dominant current route, accounting for 95% of production (2003), involves the

partial oxidation of cumene (isopropylbenzene) via the Hock rearrangement:[4]

C6H5CH(CH3)2 + O2 → C6H5OH + (CH3)2CO

Compared to most other processes, the cumene-hydroperoxide process uses relatively mild synthesis

conditions, and relatively inexpensive raw materials. However, to operate economically, there must be

demand for both phenol, and the acetone by-product.

An early commercial route, developed by Bayer and Monsanto in the early 1900's, begins with the reaction

of strong base withbenzenesulfonate [13] :

C6H5SO3H + 2 NaOH → C6H5OH + Na2SO3 + H2O

Other methods under consideration involve:

• hydrolysis of chlorobenzene, using base or steam (Raschig-Hooker process)[14]:

C6H5Cl + H2O → C6H5OH + HCl

• direct oxidation of benzene with nitrous oxide, a potentially "green" process:

C6H6 + N2O → C6H5OH + N2

• oxidation of toluene, as developed by Dow Chemical:

C6H5CH3 + 2 O2 → C6H5OH + CO2 + H2O

In the Lummus Process, the oxidation of toluene to benzoic acid is conducted

separately.

Phenol is also recoverable byproduct of coal pyrolysis[14].

[edit]Uses

The major uses of phenol, consuming two thirds of its production, involve its conversion

to plastics or related materials. Condensation with acetone givesbisphenol-A, a key

precursor to polycarbonates and epoxide resins. Condensation of phenol, alkylphenols,

or diphenols with formaldehyde gives phenolic resins, a famous example of which

is Bakelite. Hydrogenation of phenol gives cyclohexanone, 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.[4]

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

notably aspirin but also many herbicides and pharmaceuticals. Phenol is also used as

an oral anesthetic/analgesic, commonly used to temporarily treat pharyngitis.

[edit]Niche uses

Phenol is so inexpensive that it attracts many small-scale uses. It once was widely used

as an antiseptic, especially as Carbolic soap, from the early 1900s through the 1970s. It

is a component of industrial paint strippers used in the aviation industry for the removal

of epoxy, polyurethane and other chemically resistant coatings.[15]

Phenol derivatives are also used in the preparation of cosmetics including sunscreens,

[16] hair dyes, and skin lightening preparations.[17]

[edit]History

Phenol was discovered in 1834, when it was first extracted from coal tar by Friedlieb

Ferdinand Runge, which remained the primary source until the development of the

petrochemical industry.

The antiseptic properties of phenol were used by Sir Joseph Lister (1827–1912) in his

pioneering technique of antiseptic surgery, although the skin irritation caused by

continual exposure to phenol eventually led to the substitution of aseptic (germ-free)

techniques in surgery. Lister decided that the wounds themselves had to be thoroughly

cleaned. He then covered the wounds with a piece of rag or lint[18] covered in phenol, or

carbolic acid as he called it. It is also the active ingredient in some oral analgesics such

as Chloraseptic spray as well as Carmex. Phenol was also the main ingredient of

the Carbolic Smoke Ball, an ineffective device marketed in London in the 19th century

as protecting the user against influenza and other ailments, and the subject of a famous

law case.

[edit]Second World War

Injections of phenol have occasionally been used as a means of execution. In particular,

phenol and cyanide injections were used as a means of individual execution by

the Nazis during the Second World War.[19] Originally used by the Nazis in 1939 as part

of Action T4, phenol,[20] inexpensive, easy to make and quickly lethal, became the

injectable toxin of choice as part of Nazi Germany's "euthanasia" program.

[20][19][21] Although Zyklon-B pellets, invented by Gerhard Lenz, were used in the gas

chambers to exterminate large groups of people, the Nazis learned that extermination of

smaller groups was more economical via injection of each victim, one at a time, with

phenol. Phenol injections were given to thousands of people in concentration camps,

especially at Auschwitz-Birkenau. Approximately one gram is enough to cause death.

[22] Injections were administered by medical doctors, their assistants, or sometimes

prisoner doctors; such injections were originally givenintravenously, more commonly in

the arm, but injection directly into the heart, so as to induce nearly instant death, was

later adopted.[23] One of the best known inmates to be executed with a phenol injection

in Auschwitz was St. Maximilian Kolbe, a Catholic priest who volunteered to undergo

three weeks of starvation and dehydration in the place of another inmate.[23]

[edit]Occurrence

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

whisky,[24] generally ~30, but up to 100[25] ppm.

[edit]Biodegradation

Cryptanaerobacter phenolicus is a bacterium species that produces benzoate from

phenol via 4-hydroxybenzoate.[26] Rhodococcus phenolicus is a bacterium species able

to degrade phenol as sole carbon sources.[27]

[edit]Toxicity

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

[28] Repeated or prolonged skin contact with phenol may cause dermatitis, or even

second and third-degree burns due to phenol's caustic and defatting properties.

[29] Inhalation of phenol vapor may cause lung edema.[28] The substance may cause

harmful effects on the central nervous system and heart, resulting

indysrhythmia, seizures, and coma.[30] The kidneys may be affected as well. Exposure

may result in death and the effects may be delayed. Long-term or repeated exposure of

the substance may have harmful effects on the liver and kidneys."[31] There is no

evidence to believe that phenol causes cancer in humans.[32] Besides

its hydrophobic effects, another mechanism for the toxicity of phenol may be the

formation of phenoxyl radicals.[33]

Chemical burns from skin exposures can be decontaminated by washing

with polyethylene glycol,[34] isopropyl alcohol,[35] or perhaps even copious amounts of

water.[36] Removal of contaminated clothing is required, as well as

immediate hospital treatment for large splashes. This is particularly important if the

phenol is mixed with chloroform (a commonly-used mixture in molecular biology

forDNA & RNA purification from proteins).

[edit]Phenols

Main article: Phenols

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

membered aromatic ring, bonded directly to a hydroxyl group (-OH). Thus, phenols are a

class of organic compounds of which the phenol discussed in this article is the simplest

member.

[edit]See also

• Bamberger rearrangement

• Claisen rearrangement

• Cresols

• Fries rearrangement

• Polyphenol

[edit]References

• ̂  http://omlc.ogi.edu/spectra/PhotochemCAD/html/phenol.html

• ̂  Kütt, A.; Movchun, V.; Rodima, T.; Dansauer, T.; Rusanov, E. B.; Leito, I.;

Kaljurand, I.; Koppel, J.; Pihl, V.; Koppel, I.; Ovsjannikov, G.; Toom, L.; Mishima, M.;

Medebielle, M.; Lork, E.; Röschenthaler, G.-V.; Koppel, I. A.; Kolomeitsev, A. A.

Pentakis(trifluoromethyl)phenyl, a Sterically Crowded and Electron-withdrawing

Group: Synthesis and Acidity of Pentakis(trifluoromethyl)benzene, -toluene, -

phenol, and -aniline. J. Org. Chem. 2008, 73, 2607-2620. DOI: 10.1021/jo702513w

• ^ a b c Online Sigma Catalogue , accessdate: June 16, 2011.

• ^ a b c Manfred Weber, Markus Weber, Michael Kleine-Boymann "Phenol" in

Ullmann's Encyclopedia of Industrial Chemistry 2004, Wiley-

VCH.doi:10.1002/14356007.a19_299.pub2.

• ̂  Smith, Michael B.; March, Jerry (2007), Advanced Organic Chemistry: Reactions,

Mechanisms, and Structure (6th ed.), New York: Wiley-Interscience, ISBN 0-471-

72091-7

• ̂  Organic Chemistry 2nd Ed. John McMurry ISBN 0534079687

• ̂  "The Acidity of Phenol". ChemGuide. Jim Clark. Retrieved 2007-08-05.

• ̂  For further reading on the fine points of this topic, see David A. Evans's

explanation.

• ̂  Pedro J. Silva (2009). "Inductive and Resonance Effects on the Acidities of

Phenol, Enols, and Carbonyl α-Hydrogens.". J. Org. Chem. 74 (2): 914–

916. doi:10.1021/jo8018736.PMID 19053615.(Solvation effects on the relative

acidities of acetaldehyde enol and phenol described in the Supporting Information)

• ̂  David Y. Curtin and Allan R. Stein (1966). "2,6,6-Trimethyl-2,4-

Cyclohexadione.". Organic Syntheses 46: 115.

• ̂  Capponi, Marco; Gut, Ivo G.; Hellrung, Bruno; Persy, Gaby; Wirz, Jakob (1999).

"Ketonization equilibria of phenol in aqueous solution". Can. J. Chem. 77: 605–

613.doi:10.1139/cjc-77-5-6-605.

• ̂  Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter

(2001). Organic Chemistry (1st ed.). Oxford University Press. p. 531. ISBN 978-0-

19-850346-0.

• ̂  Wittcoff, H.A., Reuben, B.G. Industrial Organic Chemicals in Perspective. Part

One: Raw Materials and Manufacture. Wiley-Interscience, New York. 1980.

• ^ a b Franck, H.-G., Stadelhofer, J.W. Industrial Aromatic Chemistry. Springer-

Verlag, New York. 1988. pp. 148-155.

• ̂  "CH207 Aircraft paintstripper, phenolic, acid". Callington. 14 October 2009.

Retrieved 27 August 2011.

• ̂  A. Svobodová*, J. Psotová, and D. Walterová (2003). "Natural Phenolics in the

Prevention of UV-Induced Skin Damage. A Review". Biomed. Papers 147 (2): 137–

145.

• ̂  DeSelms, R. H.; UV-Active Phenol Ester Compounds; Enigen Science Publishing:

Washington, DC, 2008.

• ̂  Lister, Joseph (1867). "Antiseptic Principle Of The Practice Of Surgery".

• ^ a b The Experiments by Peter Tyson. NOVA

• ^ a b The Nazi Doctors, Chapter 14, Killing with Syringes: Phenol Injections. By Dr.

Robert Jay Lifton

• ̂  Euthanasia Program: Holocaust Encyclopedia

• ̂  "Phenol: Hazards and Precautions". University of Connecticut, USA. Retrieved

2011-12-02.

• ^ a b "Killing through phenol injection". Auschwitz - FINAL STATION

EXTERMINATION. Johannes Kepler University, Linz, Austria. Retrieved 2006-09-

29.

• ̂  "Peat, Phenol and PPM, by Dr P. Brossard" (PDF). Retrieved 2008-05-27.

• ̂  "Ardbeg "Supernova" Islay Single Malt Whisky".

• ̂  Cryptanaerobacter phenolicus gen. nov., sp. nov., an anaerobe that transforms

phenol into benzoate via 4-hydroxybenzoate. Pierre Juteau, Valérie Côté, Marie-

France Duckett, Réjean Beaudet, François Lépine, Richard Villemur and Jean-Guy

Bisaillon, IJSEM, January 2005, vol. 55, no. 1, pages 245-

250, doi:10.1099/ijs.0.02914-0

• ̂  Rhodococcus phenolicus sp. nov., a novel bioprocessor isolated actinomycete

with the ability to degrade chlorobenzene, dichlorobenzene and phenol as sole

carbon sources. Rehfuss M and Urban J, Syst. Appl. Microbiol. (2005), 28, pages

695-701 (Erratum: Syst. Appl. Microbiol. (2006) 29, page

182), PubMed, doi:10.1016/j.syapm.2005.05.011

• ^ a b Budavari, S, ed (1996). The Merck Index: An Encyclopedia of Chemical, Drugs,

and Biologicals. Whitehouse Station, NJ: Merck.

• ̂  Lin TM, Lee SS, Lai CS, Lin SD (June 2006). "Phenol burn".Burns: Journal of the

International Society for Burn Injuries 32(4): 517–

21. doi:10.1016/j.burns.2005.12.016.PMID 16621299.

• ̂  Warner, MA; Harper, JV (1985). "Cardiac dysrhythmias associated with chemical

peeling with phenol".Anesthesiology 62 (3): 366–7. doi:10.1097/00000542-

198503000-00030. PMID 2579602.

• ̂  World Health Organization/International Labour Organization: International

Chemical Safety Cards,http://www.inchem.org/documents/icsc/icsc/eics0070.htm

• ̂  U.S. Department of Health and Human Services. "How can phenol affect my

health?". Toxicological Profile for Phenol: 24.

• ̂  Hanscha, Corwin; McKarnsb, Susan C; Smith, Carr J; Doolittle, David J (June 15,

2000). "Comparative QSAR evidence for a free-radical mechanism of phenol-

induced toxicity". Chemico-Biological Interactions 127 (1): 61–

72.doi:10.1016/S0009-2797(00)00171-X. PMID 10903419.

• ̂  Brown, VKH; Box, VL; Simpson, BJ (1975). "Decontamination procedures for skin

exposed to phenolic substances".Archives of Environmental Health 30 (1): 1–

6.PMID 1109265.

• ̂  Hunter, DM; Timerding, BL; Leonard, RB; McCalmont, TH; Schwartz, E (1992).

"Effects of isopropyl alcohol, ethanol, and polyethylene glycol/industrial methylated

spirits in the treatment of acute phenol burns". Annals of Emergency

Medicine 21 (11): 1303–7. doi:10.1016/S0196-0644(05)81891-8.

• ̂  Pullin, TG; Pinkerton, MN; Johnson, RV; Kilian, DJ (1978). "Decontamination of

the skin of swine following phenol exposure: a comparison of the relative efficacy of

water versus polyethylene glycol/industrial methylated spirits". Toxicol Appl

Pharmacol 43 (1): 199–206. doi:10.1016/S0041-008X(78)80044-1. PMID 625760.

[edit]External links

Look up phenol in

Wiktionary, the free

dictionary.

• 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