Editing Cyclopentane

{{chembox
|Verifiedimages = changed
|Watchedfields = changed
|verifiedrevid = 444653737
|ImageFileL1_Ref = {{chemboximage|correct|??}}
|ImageFileL1 = Cyclopentane v2.svg
|ImageClassL1 = skin-invert-image
|ImageSizeL1 = 100px
|ImageAltL1 = Skeletal formula
|ImageFileR1 = Cyclopentane3d.png
|ImageClassR1 = bg-transparent
|ImageSizeR1 = 110px
|ImageAltR1 = Space-filling model
|PIN = Cyclopentane
|OtherNames = pentamethylene
|Section1 = {{Chembox Identifiers
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|ChemSpiderID = 8896
|InChI = 1/C5H10/c1-2-4-5-3-1/h1-5H2
|InChIKey = RGSFGYAAUTVSQA-UHFFFAOYAL
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChI = 1S/C5H10/c1-2-4-5-3-1/h1-5H2
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = RGSFGYAAUTVSQA-UHFFFAOYSA-N
|CASNo_Ref = {{cascite|correct|CAS}}
|CASNo=287-92-3
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = T86PB90RNU
|PubChem=9253
|ChEBI_Ref = {{ebicite|correct|EBI}}
|ChEBI = 23492
|SMILES=C1CCCC1
|RTECS=GY2390000
|EINECS = 206-016-6
}}
|Section2 = {{Chembox Properties
|Formula=C<sub>5</sub>H<sub>10</sub>
|MolarMass=70.1 g/mol
|Appearance=clear, colorless liquid
|Odor = mild, sweet
|Density=0.751 g/cm<sup>3</sup>
|MeltingPtC=-93.9
|BoilingPtC=49.2
|Solubility=156 mg·l<sup>−1</sup> (25 °C)<ref>{{GESTIS|ZVG=27960|CAS=287-92-3|Name=cyclopentane|Date=28 February 2015}}</ref>
|SolubleOther = soluble in [[ethanol]], [[acetone]], [[diethyl ether|ether]]
|pKa = ~45
|RefractIndex = 1.4065
|VaporPressure = 45 [[kPa]] (20 °C) <ref>{{cite web |url=http://www.ilo.org/dyn/icsc/showcard.display?p_version=2&p_card_id=0353 |title = ICSC 0353 - CYCLOPENTANE}}</ref>
|MagSus = −59.18·10<sup>−6</sup> cm<sup>3</sup>/mol
}}
|Section3 = {{Chembox Hazards
|MainHazards=Flammable<ref name=PGCH/>
|FlashPtC = -37.2
|AutoignitionPtC = 361
|NFPA-H = 1 | NFPA-F = 3 | NFPA-R = 0
|PEL = none<ref name=PGCH>{{PGCH|0171}}</ref>
|ExploLimits = 1.1%–8.7%<ref name=PGCH/>
|IDLH = N.D.<ref name=PGCH/>
|REL = TWA 600 ppm (1720 mg/m<sup>3</sup>)<ref name=PGCH/> 
}}
|Section4 = {{Chembox Related
|OtherCompounds = [[cyclopropane]], [[cyclobutane]], [[cyclohexane]]
}}
}}
'''Cyclopentane''' (also called '''C pentane''')<ref>{{cite journal |last1=Sárkány |first1=A. |last2=Gaál |first2=J. |last3=Toth |first3=L. |title=Comparative Study of C-Pentane and N-Pentane Transformations on Ni and Pt Catalysts |journal=Studies in Surface Science and Catalysis |date=1981 |volume=7 |pages=291–301 |doi=10.1016/S0167-2991(09)60278-0}}</ref> is a highly [[flammable]] [[alicyclic compound|alicyclic]] [[hydrocarbon]] with [[chemical formula]] [[C5H10|C<sub>5</sub>H<sub>10</sub>]] and [[CAS number]] 287-92-3, consisting of a ring of five [[carbon]] atoms each bonded with two [[hydrogen]] atoms above and below the plane. It is a colorless [[liquid]] with a [[petrol]]-like [[odor]]. Its [[freezing point]] is −94 °C and its [[boiling point]] is 49 °C. Cyclopentane is in the class of [[cycloalkane]]s, being [[alkane]]s that have one or more [[carbon ring]]s. It is formed by [[cracking (chemistry)|cracking]] [[cyclohexane]] in the presence of [[alumina]] at a high temperature and pressure.

It was first prepared in 1893 by the German chemist [[Johannes Wislicenus]].<ref>{{cite journal |last1=Wislicenus |first1=J. |last2=Hentschel |first2=W. |title=III. Der Pentamethenylalkohol und seine Derivate (Cyclopentanol and its derivatives)|journal=Justus Liebigs Annalen der Chemie |date=January 1893 |volume=275 |issue=2-3 |pages=322–330 |doi=10.1002/jlac.18932750216 | url=https://zenodo.org/records/1657308/files/article.pdf}}</ref>

==Production, occurrence and use==
Cycloalkanes are formed by [[catalytic reforming]]. For example, when passed over a hot platinum surface, [[2-Methylbutane|2-methylbutane]] converts into cyclopentane.

[[File:Cyclopentane warning on refrigerator.jpg|thumb|left|This prominent sign on the back of a refrigerator marks it as containing cyclopentane-based insulation]]
Cyclopentane is principally used as a [[blowing agent]] in the manufacture of [[polyurethane foam|polyurethane insulating foam]], replacing ozone-depleting agents such as [[Trichlorofluoromethane|CFC-11]] and [[1,1-Dichloro-1-fluoroethane|HCFC-141b]].<ref name="Schilling2000">{{cite journal | last1 = Schilling | first1 = S. L. | title = Appliance Rigid Foams Blown with Cyclopentane and Cyclopentane/Isopentane Blends | journal = Journal of Cellular Plastics | date = May 2000 | volume = 36 | issue = 3 | pages = 190–206 | issn = 0021-955X | eissn = 1530-7999 | doi = 10.1177/0021955X0003600302 | pmid = | url = }}</ref><ref name=greenpeace>[http://archive.greenpeace.org/ozone/excuse/20excuse.html Greenpeace - Appliance Insulation] {{webarchive|url=https://web.archive.org/web/20081030041552/http://archive.greenpeace.org/ozone/excuse/20excuse.html |date=2008-10-30 }}</ref> While cyclopentane is not typically used as a [[refrigerant]], it is common for domestic appliances that are insulated with cyclopentane-based foam, such as [[refrigerator]]s and [[freezer]]s, to be marked with cyclopentane warning labels due to its flammability. Cyclopentane is also used in the manufacture of [[chemical synthesis|synthetic]] [[resin]]s and [[rubber]] [[adhesive]]s.{{Citation needed|date=June 2024}}

Cyclopentane is a minor component of automobile fuel, with its share in US [[gasoline]] varying between 0.2 and 1.6% in early 1990s<ref>{{Cite journal |last=Doskey |first=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 |issn=1047-3289}}</ref> and 0.1 to 1.7% 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> Its research and motor [[Octane rating|octane numbers]] are reported as 101 or 103 and 85 or 86 respectively.<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=1990-08-31 |publisher=CRC Press |isbn=978-0-8247-8399-0 |pages=9 |language=en}}</ref><ref>{{Cite journal |last=Song |first=Hwasup |last2=Dauphin |first2=Roland |last3=Vanhove |first3=Guillaume |date=2020 |title=A kinetic investigation on the synergistic low-temperature reactivity, antagonistic RON blending of high-octane fuels: Diisobutylene and cyclopentane |url=https://hal.archives-ouvertes.fr/hal-02902174/file/Ternary%20blend_R1_websharing.pdf |journal=Combustion and Flame |volume=220 |pages=23–33 |doi=10.1016/j.combustflame.2020.06.030 |issn=0010-2180}}</ref>

Multiple alkylated cyclopentane (MAC) lubricants, such as 1,3,4-tri-(2-octyldodecyl) cyclopentane, have low volatility and are used by NASA in space applications.<ref name="NASA">{{cite tech report |last1=Loewenthal |first1=Stuart H. |last2=Jones |first2=William R. |last3=Predmore |first3=Roamer E. |title=Life of Pennzane and 815Z-Lubricated Instrument Bearings Cleaned with Non-CFC Solvents |date=1 September 1999 |url=https://ntrs.nasa.gov/citations/19990039657 |publisher=National Aeronautics and Space Administration |location=John H. Glenn Research Center at Lewis Field |language=en |oclc=1002210567 |id=19990039657 }}</ref><ref>{{cite web | title=Pennzoil Products: High Tech Products | website=pennzane.com | date=12 April 2004 | url=http://pennzane.com/ | archive-url=https://web.archive.org/web/20040412141718/http://pennzane.com/ | archive-date=12 April 2004 | url-status=dead | access-date=15 July 2022}}</ref>

Cyclopentane requires safety precautions to prevent leakage and ignition as it is both highly flammable and can also cause respiratory arrest when inhaled.<ref>{{cite journal | author=Robert W. Virtue, M.D. | title=OBSERVATIONS ON CYCLOPENTANE AS AN ANESTHETIC AGENT | journal=Anesthesiology | volume=10 | date=May 1949 | pages=318–324 | doi=10.1097/00000542-194905000-00007}}</ref>

Cyclopentane can be fluorinated to give compounds ranging from {{chem2|C5H9F}} to [[perfluorocyclopentane]] {{chem2|C5F10}}. Such species are conceivable refrigerants and specialty solvents.<ref name="Tatlow 1995">{{cite journal | last=Tatlow | first=John Colin | title=Cyclic and bicyclic polyfluoro-alkanes and -alkenes | journal=Journal of Fluorine Chemistry |  volume=75 | issue=1 | year=1995 | issn=0022-1139 | doi=10.1016/0022-1139(95)03293-m | pages=7–34}}</ref><ref>{{cite journal |last1=Zhang |first1=Chengping |last2=Qing |first2=Feiyao |last3=Quan |first3=Hengdao |last4=Sekiya |first4=Akira |title=Synthesis of 1,1,2,2,3,3,4-heptafluorocyclopentane as a new generation of green solvent |journal=Journal of Fluorine Chemistry |date=January 2016 |volume=181 |pages=11–16 |doi=10.1016/j.jfluchem.2015.10.012}}</ref>

The cyclopentane ring is pervasive in [[natural product]]s including many useful drugs.  Examples include most [[steroid]]s, [[prostaglandin]]s, and some [[lipid]]s.

==Conformations==

In a [[regular pentagon]], the angles at the vertices are all 108°, slightly less than the bond angle in perfectly tetrahedrally bonded carbon, which is about 109.47°. However, cyclopentane is not planar in its normal [[Conformational isomerism|conformations]]. It puckers in order to increase the distances between the hydrogen atoms (something which does not happen in the planar [[cyclopentadienyl anion]] {{chem2|C5H5-}} because it doesn't have as many hydrogen atoms). This means that the average C-C-C angle is less than 108°. There are two conformations that give local minima of the energy, the "envelope" and the "half-chair". The envelope has mirror symmetry ([[Point groups in three dimensions|C{{sub|s}}]]), while the half chair has two-fold rotational symmetry ([[Point groups in three dimensions|C{{sub|2}}]]). In both cases the symmetry implies that there are two pairs of equal C-C-C angles and one C-C-C angle that has no pair. In fact for cyclopentane, unlike for [[cyclohexane]] (C<sub>6</sub>H<sub>12</sub>, see [[cyclohexane conformation]]) and higher [[cycloalkane]]s, it is not possible geometrically for all the angles and bond lengths to be equal except if it is in the form of a flat regular pentagon.

<gallery>
File:Cyclopentane envelope conformation.svg|Envelope
File:Cyclopentane3D.png|3D envelope
File:Cyclopentane halfchair.svg|Half-chair
</gallery>

==References==
{{reflist}}

==External links==
*{{Commons category-inline|Cyclopentane}}
{{cycloalkanes}}
{{Authority control}}

[[Category:Cyclopentanes]]
[[Category:Hydrocarbon solvents]]
[[Category:Cycloalkanes]]