Cyclopentane

Cyclopentane 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 occurs as a colorless liquid with a petrol-like odor. Its melting 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 rings of carbon atoms. It is formed by cracking cyclohexane in the presence of alumina at a high temperature and pressure.

Cyclopentane
Skeletal formula
Space-filling model
Names
IUPAC name
Cyclopentane
Other names
pentamethylene
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.005.470
EC Number
  • 206-016-6
RTECS number
  • GY2390000
UNII
Properties
C5H10
Molar mass 70.1 g/mol
Appearance clear, colorless liquid
Odor mild, sweet
Density 0.751 g/cm3
Melting point −93.9 °C (−137.0 °F; 179.2 K)
Boiling point 49.2 °C (120.6 °F; 322.3 K)
156 mg·l−1 (25 °C)[1]
Solubility soluble in ethanol, acetone, ether
Vapor pressure 45 kPa (20 °C) [2]
Acidity (pKa) ~45
-59.18·10−6 cm3/mol
1.4065
Hazards
Main hazards Flammable[3]
NFPA 704 (fire diamond)
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
1
0
Flash point −37.2 °C (−35.0 °F; 236.0 K)
361 °C (682 °F; 634 K)
Explosive limits 1.1%-8.7%[3]
NIOSH (US health exposure limits):
PEL (Permissible)
none[3]
REL (Recommended)
TWA 600 ppm (1720 mg/m3)[3]
IDLH (Immediate danger)
N.D.[3]
Related compounds
Related compounds
cyclopropane, cyclobutane, cyclohexane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

It was first prepared in 1893 by the German chemist Johannes Wislicenus.[4]

Industrial usage

Cyclopentane is used in the manufacture of synthetic resins and rubber adhesives and also as a blowing agent in the manufacture of polyurethane insulating foam, as found in many domestic appliances such as refrigerators and freezers, replacing alternatives such as CFC-11 and HCFC-141b.[5]

Multiply alkylated cyclopentane (MAC) lubricants have low volatility and are used in some specialty applications.[6]

Formulation of cycloalkanes

Cycloalkanes can be formulated via a process known as catalytic reforming.

For example, 2-methylbutane can be reformed into cyclopentane, by use of a platinum catalyst. This is particularly well known in automobiles, as branched alkanes will burn much more readily.

Conformations

References

  1. Record of cyclopentane in the GESTIS Substance Database of the Institute for Occupational Safety and Health, accessed on 28 February 2015.
  2. http://www.ilo.org/dyn/icsc/showcard.display?p_version=2&p_card_id=0353
  3. NIOSH Pocket Guide to Chemical Hazards. "#0171". National Institute for Occupational Safety and Health (NIOSH).
  4. J. Wislicenus and W. Hentschel (1893) "Der Pentamethenylalkohol und seine Derivate" (Cyclopentanol and its derivatives), Annalen der Chemie, 275 : 322-330; see especially pages 327-330. Wislicenus prepared cyclopentane from cyclopentanone ("Ketopentamethen"), which is prepared by heating calcium adipate.
  5. Greenpeace - Appliance Insulation Archived 2008-10-30 at the Wayback Machine
  6. Pennzane - lubrication technology
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