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=C5H10
|MolarMass=70.1 g/mol
|Appearance=clear, colorless liquid
|Odor = mild, sweet
|Density=0.751 g/cm3
|MeltingPtC=-93.9
|BoilingPtC=49.2
|Solubility=156 mg·l−1 (25 °C){{GESTIS|ZVG=27960|CAS=287-92-3|Name=cyclopentane|Date=28 February 2015}}
|SolubleOther = soluble in ethanol, acetone, ether
|pKa = ~45
|RefractIndex = 1.4065
|VaporPressure = 45 kPa (20 °C) {{cite web |url=http://www.ilo.org/dyn/icsc/showcard.display?p_version=2&p_card_id=0353 |title = ICSC 0353 - CYCLOPENTANE}}
|MagSus = −59.18·10−6 cm3/mol
}}
|Section3 = {{Chembox Hazards
|FlashPtC = -37.2
|AutoignitionPtC = 361
|NFPA-H = 1 | NFPA-F = 3 | NFPA-R = 0
|PEL = none{{PGCH|0171}}
|REL = TWA 600 ppm (1720 mg/m3)
}}
|Section4 = {{Chembox Related
|OtherCompounds = cyclopropane, cyclobutane, cyclohexane
}}
}}
Cyclopentane (also called C pentane){{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}} is a highly flammable alicyclic hydrocarbon with chemical formula C5H10 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 cycloalkanes, being alkanes that have one or more carbon rings. It is formed by 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.{{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}}
Production, occurrence and use
Cycloalkanes are formed by catalytic reforming. For example, when passed over a hot platinum surface, 2-methylbutane converts into cyclopentane.
File:Cyclopentane warning on refrigerator.jpg
Cyclopentane is principally used as a blowing agent in the manufacture of polyurethane insulating foam, replacing ozone-depleting agents such as CFC-11 and HCFC-141b.{{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 = }}[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 }} While cyclopentane is not typically used as a refrigerant, it is common for domestic appliances that are insulated with cyclopentane-based foam, such as refrigerators and freezers, to be marked with cyclopentane warning labels due to its flammability. Cyclopentane is also used in the manufacture of synthetic resins and rubber adhesives.{{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{{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}} and 0.1 to 1.7% in 2011.{{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}} Its research and motor octane numbers are reported as 101 or 103 and 85 or 86 respectively.{{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}}{{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}}
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.{{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 }}{{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}}
Cyclopentane requires safety precautions to prevent leakage and ignition as it is both highly flammable and can also cause respiratory arrest when inhaled.{{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}}
Cyclopentane can be fluorinated to give compounds ranging from {{chem2|C5H9F}} to perfluorocyclopentane {{chem2|C5F10}}. Such species are conceivable refrigerants and specialty solvents.{{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}}{{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}}
The cyclopentane ring is pervasive in natural products including many useful drugs. Examples include most steroids, prostaglandins, and some lipids.
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 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), while the half chair has two-fold rotational symmetry (Point groups in three dimensions). 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 (C6H12, see cyclohexane conformation) and higher cycloalkanes, 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.
File:Cyclopentane envelope conformation.svg|Envelope
File:Cyclopentane3D.png|3D envelope
File:Cyclopentane halfchair.svg|Half-chair
References
{{reflist}}
External links
- {{Commons category-inline|Cyclopentane}}
{{cycloalkanes}}
{{Authority control}}