View source for Pentane

{{short description|Alkane with 5 carbon atoms C5H12}}
{{Chembox
|Watchedfields = changed
|verifiedrevid = 464198186
|ImageFileL1 = Pentane-2D-Skeletal.svg
|ImageClassL1 = skin-invert-image
|ImageSizeL1 = 160
|ImageAltL1 = Skeletal formula of pentane
|ImageFileR1 = Structure of n-Pentan.svg
|ImageClassR1 = skin-invert-image
|ImageSizeR1 = 160
|ImageAltR1 = Skeletal formula of pentane with all explicit hydrogens added
|ImageFileL2 = Pentane-3D-balls.png
|ImageClassL2 = bg-transparent
|ImageFileL2_Ref = {{chemboximage|correct|??}}
|ImageSizeL2 = 120
|ImageAltL2 = Pentane 3D ball.png
|ImageFileR2 = Pentane-3D-space-filling.png
|ImageClassR2 = bg-transparent
|ImageFileR2_Ref = {{chemboximage|correct|??}}
|ImageSizeR2 = 120
|ImageAltR2 = Pentane 3D spacefill.png
|PIN = Pentane<ref>{{cite book |author=[[International Union of Pure and Applied Chemistry]] |date=2014 |title=Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 |publisher=[[Royal Society of Chemistry|The Royal Society of Chemistry]] |page=59 |doi=10.1039/9781849733069 |isbn=978-0-85404-182-4}}</ref>
|OtherNames = Quintane;<ref>{{cite journal|title=I. On the action of trichloride of phosphorus on the salts of the aromatic monamines|first=August Wilhelm Von|last=Hofmann|date=1 January 1867|journal=Proceedings of the Royal Society of London|volume=15|pages=54–62|doi=10.1098/rspl.1866.0018|s2cid=98496840}}</ref> Refrigerant-4-13-0
|Section1 = {{Chembox Identifiers
|CASNo = 109-66-0
|CASNo_Ref = {{cascite|correct|CAS}}
|PubChem = 8003
|ChemSpiderID = 7712
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|UNII = 4FEX897A91
|UNII_Ref = {{fdacite|correct|FDA}}
|EINECS = 203-692-4
|UNNumber = 1265
|DrugBank = DB03119
|DrugBank_Ref = {{drugbankcite|correct|drugbank}}
|MeSHName = pentane
|ChEBI = 37830
|ChEBI_Ref = {{ebicite|correct|EBI}}
|ChEMBL = 16102
|ChEMBL_Ref = {{ebicite|correct|EBI}}
|RTECS = RZ9450000
|Beilstein = 969132
|Gmelin = 1766
|SMILES = CCCCC
|StdInChI = 1S/C5H12/c1-3-5-4-2/h3-5H2,1-2H3
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = OFBQJSOFQDEBGM-UHFFFAOYSA-N
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
}}
|Section2 = {{Chembox Properties
|Properties_ref = <ref name="GESTIS">{{GESTIS|ZVG=10040|CAS=109-66-0|Name=n-Pentane|Date=19 April 2011}}</ref>
|C=5 | H=12
|Appearance = Colourless liquid
|Odor = Gasoline-like<ref name=PGCH/>
|Density = 0.626 g/mL; 0.6262 g/mL (20&nbsp;°C)
|MeltingPtK = 142.7 to 144.1
|BoilingPtK = 309.0 to 309.4
|Solubility = 40 mg/L (20&nbsp;°C)
|LogP = 3.255
|VaporPressure = 57.90 kPa (20.0&nbsp;°C)
|HenryConstant = 7.8 nmol Pa<sup>−1</sup> kg<sup>−1</sup>
|pKa = ~45
|pKb = ~59
|LambdaMax = 200 nm
|RefractIndex = 1.358
|Viscosity = 0.240 mPa·s (at 20&nbsp;°C)
|MagSus = −63.05·10<sup>−6</sup> cm<sup>3</sup>/mol
}}
|Section3 = {{Chembox Thermochemistry
|DeltaHf = −174.1–−172.9 kJ mol<sup>−1</sup>
|DeltaHc = −3.5095–−3.5085 MJ mol<sup>−1</sup>
|Entropy = 263.47 J K<sup>−1</sup> mol<sup>−1</sup>
|HeatCapacity = 167.19 J K<sup>−1</sup> mol<sup>−1</sup>
}}
|Section4 = {{Chembox Hazards
|GHSPictograms = {{GHS flame}} {{GHS exclamation mark}} {{GHS health hazard}} {{GHS environment}}
|GHSSignalWord = '''DANGER'''
|HPhrases = {{H-phrases|225|304|336|411}}
|PPhrases = {{P-phrases|210|261|273|301+310|331}}
|NFPA-H = 1
|NFPA-F = 4
|NFPA-R = 0
|FlashPtC = −49.0
|AutoignitionPtC = 260.0
|ExploLimits = 1.5–7.8%<ref name=PGCH/>
|LD50 = {{Unbulleted list|3 g kg<sup>−1</sup> <small>(dermal, rabbit)</small>|5 g kg<sup>−1</sup> <small>(oral, mouse)</small>}}
|IDLH = 1500 ppm<ref name=PGCH>{{PGCH|0486}}</ref>
|REL = TWA 120 ppm (350 mg/m<sup>3</sup>) C 610 ppm (1800 mg/m<sup>3</sup>) [15-minute]<ref name=PGCH/>
|PEL = TWA 1000 ppm (2950 mg/m<sup>3</sup>)<ref name=PGCH/>
|LC50 = 130,000 mg/m<sup>3</sup> (mouse, 30 min)<br/>128,200 ppm (mouse, 37 min)<br/>325,000 mg/m<sup>3</sup> (mouse, 2 hr)<ref>{{IDLH|109660|n-Pentane}}</ref>
}}
|Section5 = {{Chembox Related
|OtherFunction_label = alkanes
|OtherFunction = {{Unbulleted list|[[Butane]]|[[Butyl iodide]]|[[Hexane]]}}
}}
}}
'''Pentane''' is an [[organic compound]] with the [[chemical formula|formula]] C<sub>5</sub>H<sub>12</sub>—that is, an [[alkane]] with five [[carbon]] atoms. The term may refer to any of three [[structural isomerism|structural isomers]], or to a mixture of them: in the [[IUPAC]] nomenclature, however, '''pentane''' means exclusively the ''n''-pentane isomer, in which case [[pentanes]] refers to a mixture of them; the other two are called [[isopentane]] (methylbutane) and [[neopentane]] (dimethylpropane). [[Cyclopentane]] is not an isomer of pentane because it has only 10 [[hydrogen]] atoms where pentane has 12.

Pentanes are components of some fuels and are employed as specialty [[solvent]]s in the [[laboratory]]. Their properties are very similar to those of [[butane]]s and [[hexane]]s.

== History ==
Normal pentane was discovered in 1862 by [[Carl Schorlemmer]], who, while analyzing pyrolysis products of the [[cannel coal]] mined in [[Wigan]], identified, separated by [[fractional distillation]] and studied a series of liquid hydrocarbons inert to [[Nitric acid|nitric]] and [[Sulfuric acid|sulfuric]] acids. The lightest of them, which he called '''hydride of amyl''', had an [[empirical formula]] of C<sub>5</sub>H<sub>12</sub>, density of 0.636 at 17&nbsp;°C and boiled between 39 and 40&nbsp;°C.<ref>{{Cite journal |last=Schorlemmer |first=C. |date=1862 |title=On the hydrides of the alcohol-radicles existing in the products of the destructive distillation of cannel coal |url=https://books.google.com/books?id=51fYFmBb7_kC&pg=PA419 |journal=Journal of the Chemical Society |language=en |volume=15 |pages=419–427 |doi=10.1039/JS8621500419 |issn=0368-1769}}</ref> In the next year he identified the same compound in the [[Pennsylvania oil rush|Pennsylvanian oil]].<ref>{{Cite book |last= |first= |url=https://books.google.com/books?id=fTw9AQAAMAAJ&pg=RA1-PA81 |title=Proceedings of the Literary and Philosophical Society of Manchester |date=1864 |language=en}}</ref> By 1872 he switched his nomenclature to the modern one, leading to it being called Pentane.<ref>{{Cite journal |last=Schorlemmer |first=Carl |date=1872 |title=On the normal paraffins |url=https://books.google.com/books?id=Sow5AQAAMAAJ&pg=PA113 |journal=Philosophical Transactions of the Royal Society of London |volume=162 |pages=111–123 |doi=10.1098/rstl.1872.0007|url-access=subscription }}</ref>

Beyond Schorlemmer's initial work, scientists discovered that the molecular formula C<sub>5</sub>H<sub>12</sub> could represent different structural arrangements, leading to the identification of [[isopentane]] and [[neopentane]]. This discovery contributed significantly to the understanding of [[Isomer|isomerism]] and [[Hydrocarbon|hydrocarbons]] in the 19th century. The high volatility and low boiling point of pentane made it useful as a solvent and in fuels. Its use expanded in the 1970s as a blowing agent for foams, replacing [[Chlorofluorocarbon|CFCs]]. The petroleum refining industry utilizes pentanes, particularly isopentane, to produce high-octane fuels. 

==Isomers==
{{main|C5H12}}
{| class="wikitable" style="text-align:left"
|- 
| bgcolor="#ddeeff" |Common name
|'''normal pentane'''<br/>'''unbranched pentane'''<br/>'''''n''-pentane'''
|'''[[isopentane]]'''
|'''[[neopentane]]'''
|-
| bgcolor="#ddeeff" |IUPAC name
|'''pentane'''
|'''2-methylbutane'''
|'''2,2-dimethylpropane'''
|- 
| bgcolor="#ddeeff" |[[Molecular diagram]]
|[[File:N-Pentan.png|130px]]
|[[File:Isopentane1.svg|140px]]
|[[File:Neopentane.svg|120px]]
|- 
| bgcolor="#ddeeff" |[[Skeletal diagram]]
|[[File:Pentane-2D-Skeletal.svg|150px]]
|[[File:Isopentane-2D-skeletal.svg|110px]]
|[[File:Neopentane-2D-skeletal.svg|80px]] 
|-
| bgcolor="#ddeeff" |[[Melting point]] (°C)<ref name="Wei2">{{cite journal | doi = 10.1021/ie990588m| title = Molecular Symmetry, Rotational Entropy, and Elevated Melting Points| date = 1999| last1 = Wei| first1 = James| journal = Industrial & Engineering Chemistry Research| volume = 38| issue = 12| pages = 5019–5027}}</ref>
| &minus;129.8
| &minus;159.9
| &minus;16.6
|-
| bgcolor="#ddeeff" |[[Boiling point]] (°C)<ref name="Wei2"/>
| 36.0
| 27.7
| 9.5
|-
| bgcolor="#ddeeff" |[[Density]]<br/>(0&nbsp;°C,kg/m<sup>3</sup>)<ref name="Wei2"/>
| 699

| 616
| 586
|}

==Industrial uses==
Pentanes are some of the primary [[blowing agent]]s used in the production of [[polystyrene foam]] and other foams. Usually, a mixture of n-, i-, and increasingly cyclopentane is used for this purpose.

Acid-catalyzed isomerization gives isopentane, which is used in producing high-octane fuels.<ref name=Ullmanns>{{cite encyclopedia |author=Karl Griesbaum |author2=Arno Behr |author3=Dieter Biedenkapp |author4=Heinz-Werner Voges |author5=Dorothea Garbe |author6=Christian Paetz |author7=Gerd Collin |author8=Dieter Mayer |author9=Hartmut Höke |chapter=Hydrocarbons|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|year=2002|publisher=Wiley-VCH|place=Weinheim|doi=10.1002/14356007.a13_227|isbn=978-3-527-30673-2}}</ref>

Because of their low [[boiling point]]s, low cost, and relative safety, pentanes are used as a [[working fluid|working medium]] in [[geothermal power]] stations and [[organic Rankine cycle]]s. It is also used in some blended [[refrigerant]]s.

Pentanes are solvents in many ordinary products, e.g. in some [[pesticide]]s.<ref name=Milne>{{cite book|editor-last=Milne|editor-first=G. W. A.|title=Gardner's Commercially Important Chemicals: Synonyms, Trade Names, and Properties|date=2005|publisher=John Wiley & Sons, Inc|location=Hoboken, New Jersey|isbn=978-0-471-73518-2|page=477}}</ref>

==Laboratory use==
Pentanes are relatively inexpensive and are the most [[Volatile organic compound|volatile]] liquid alkanes at room temperature, so they are often used in the laboratory as [[solvent]]s that can be conveniently and rapidly evaporated. However, because of their [[nonpolar]]ity and lack of [[functional group|functionality]], they dissolve only nonpolar and alkyl-rich compounds. Pentanes are [[miscible]] with most common nonpolar solvents such as [[chlorocarbon]]s, [[aromatic]]s, and [[ether]]s.

They are often used in [[chromatography#Liquid chromatography|liquid chromatography]].

==Physical properties==
The [[boiling point]]s of the pentane isomers range from about 9 to 36&nbsp;°C. As is the case for other alkanes, the more thickly branched isomers tend to have lower boiling points.

The same tends to be true for the [[melting point]]s of alkane isomers, and that of isopentane is 30&nbsp;°C lower than that of ''n''-pentane. However, the melting point of [[neopentane]], the most heavily branched of the three, is 100&nbsp;°C ''higher'' than that of isopentane. The anomalously high melting point of neopentane has been attributed to the [[Tetrahedron|tetrahedral]] [[molecule]]s packing more closely in solid form; this explanation is contradicted by the fact that neopentane has a lower density than the other two isomers,<ref name="Wei">{{cite journal | last=Wei | first=James | title=Molecular Symmetry, Rotational Entropy, and Elevated Melting Points | journal=Industrial & Engineering Chemistry Research | publisher=American Chemical Society (ACS) | volume=38 | issue=12 | year=1999 | issn=0888-5885 | doi=10.1021/ie990588m | pages=5019–5027}}</ref> and the high melting point is actually caused by neopentane's significantly lower [[entropy of fusion]].

The branched [[isomer]]s are more stable (have lower [[heat of formation]] and [[heat of combustion]]) than n-pentane. The difference is 1.8 [[KCal|kcal]]/[[Mole (unit)|mol]] for isopentane, and 5 kcal/mol for neopentane.<ref>From the values listed at [[Standard enthalpy change of formation (data table)]].</ref><ref name="Good 1970 pp. 237–244">{{cite journal | last=Good | first=W.D | title=The enthalpies of combustion and formation of the isomeric pentanes | journal=The Journal of Chemical Thermodynamics | publisher=Elsevier BV | volume=2 | issue=2 | year=1970 | issn=0021-9614 | doi=10.1016/0021-9614(70)90088-1 | pages=237–244 | bibcode=1970JChTh...2..237G }}</ref>

[[Rotation]] about two central single C-C [[Chemical bond|bonds]] of ''n''-pentane produces four different [[conformational isomerism|conformations]].<ref name=Balabin_2009>{{cite journal |journal=J. Phys. Chem. A |volume = 113 |issue = 6 |pages = 1012–9 |doi=10.1021/jp809639s |title=Enthalpy Difference between Conformations of Normal Alkanes: Raman Spectroscopy Study of n-Pentane and n-Butane |year=2009 |author=Roman M. Balabin |pmid=19152252|bibcode = 2009JPCA..113.1012B |author-link = Roman Balabin }}</ref>

==Reactions==
Like other [[alkanes]], pentanes are largely unreactive at standard room temperature and conditions - however, with sufficient [[activation energy]] (e.g., an open flame), they readily [[Redox|oxidize]] to form [[carbon dioxide]] and water:
:C<sub>5</sub>H<sub>12</sub> + 8 O<sub>2</sub> → 5 CO<sub>2</sub> + 6 H<sub>2</sub>O + heat/energy

Like other [[alkanes]], pentanes undergo [[free radical]] [[free radical halogenation|chlorination]]:
:C<sub>5</sub>H<sub>12</sub> + Cl<sub>2</sub> → C<sub>5</sub>H<sub>11</sub>Cl + HCl
Without zeolite catalysts, such reactions are unselective, so with ''n''-pentane, the result is a mixture of the 1-, 2-, and 3-chloropentanes, as well as more highly chlorinated derivatives. Other radical [[halogenation]]s can also occur.

==Production and occurrence==
Pentane is produced by [[fractional distillation]] of [[petroleum]] and purified by [[Rectification (chemical/process engineering)|rectification]] (successive distillations).<ref name="PubChem">{{Cite web|title=Pentane|url=https://pubchem.ncbi.nlm.nih.gov/compound/Pentane|access-date=2023-06-29|website=PubChem}}</ref>

It occurs in alcoholic beverages and in [[hops|hop oil]].<ref name="PubChem" /> It is a component of exhaled breath for some individuals. A degradation product of unsaturated fatty acids, its presence is associated with some diseases and cancers.<ref>{{cite journal|doi=10.1016/S0378-4347(99)00127-9|pmid=10410929|title=Variation in volatile organic compounds in the breath of normal humans|journal=Journal of Chromatography B: Biomedical Sciences and Applications|volume=729|issue=1–2|pages=75–88|year=1999|last1=Phillips|first1=Michael|last2=Herrera|first2=Jolanta|last3=Krishnan|first3=Sunithi|last4=Zain|first4=Mooena|last5=Greenberg|first5=Joel|last6=Cataneo|first6=Renee N.}}</ref>

Pentane is a relatively minor component of automobile [[gasoline]], with its share varying within 1–6% in 1990s Sweden,<ref>{{Cite journal |last1=Östermark |first1=Ulf |last2=Petersson |first2=Göran |date=1992-09-01 |title=Assessment of hydrocarbons in vapours of conventional and alkylate-based petrol |url=https://publications.lib.chalmers.se/records/fulltext/local_72590.pdf |journal=Chemosphere |volume=25 |issue=6 |pages=763–768 |doi=10.1016/0045-6535(92)90066-Z |bibcode=1992Chmsp..25..763O |issn=0045-6535}}</ref> 2–13% in 1990s US<ref>{{Cite journal |last1=Doskey |first1=Paul V. |last2=Porter |first2=Joseph A. |last3=Scheff |first3=Peter A. |date=November 1992 |title=Source Fingerprints for Volatile Non-Methane Hydrocarbons |url=https://www.tandfonline.com/doi/full/10.1080/10473289.1992.10467090 |journal=Journal of the Air & Waste Management Association |language=en |volume=42 |issue=11 |pages=1437–1445 |doi=10.1080/10473289.1992.10467090 |bibcode=1992JAWMA..42.1437D |issn=1047-3289}}</ref> and 1–3% in the US in 2011.<ref>{{cite web |date=2011 |title=Hydrocarbon Composition of Gasoline Vapor Emissions from Enclosed Fuel Tanks |url=https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P100GPED.TXT |website=nepis.epa.gov |publisher=United States Environmental Protection Agency}}</ref> At 62, its octane number (both RON and MON) is quite low.<ref>{{Cite book |last=Scherzer |first=Julius |url=https://books.google.com/books?id=0R2qSCsVT3cC&pg=PA9 |title=Octane-Enhancing Zeolitic FCC Catalysts: Scientific and Technical Aspects |date=1990 |publisher=CRC Press |isbn=978-0-8247-8399-0 |pages=9 |language=en}}</ref>

==References==
{{Reflist}}

==External links==
* [https://www.inchem.org/documents/icsc/icsc/eics0534.htm International Chemical Safety Card 0534] at ILO.org
* [https://www.cdc.gov/niosh/npg/npgd0486.html NIOSH Pocket Guide to Chemical Hazards] at CDC.gov
* [https://web.archive.org/web/20150923173922/http://www.ars-grin.gov/cgi-bin/duke/chemical.pl?PENTANE Phytochemical data for pentane] at Ars-grin.gov

{{Alkanes}}
{{Hydrides by group}}

[[Category:Alkanes]]
[[Category:Hydrocarbon solvents]]