World Library  
Flag as Inappropriate
Email this Article

Pentane

Article Id: WHEBN0000660161
Reproduction Date:

Title: Pentane  
Author: World Heritage Encyclopedia
Language: English
Subject: Alkane, Natural gas, Alkanes, Structural isomer, Natural-gas processing
Collection: Alkanes, Hydrocarbon Solvents
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Pentane

Pentane
Skeletal formula of pentane
Skeletal formula of pentane with all explicit hydrogens added
Pentane 3D ball.png
Pentane 3D spacefill.png
Names
IUPAC name
Pentane
Identifiers
 Y
969132
ChEBI  Y
ChEMBL  Y
ChemSpider  Y
DrugBank  Y
EC number 203-692-4
1766
Jmol-3D images Image
MeSH
PubChem
RTECS number RZ9450000
UNII  Y
UN number 1265
Properties[1]
C5H12
Molar mass 72.15 g·mol−1
Appearance Colourless liquid
Odor Gasoline-like[2]
Density 0.626 g mL−1
Melting point −130.5 to −129.1 °C; −202.8 to −200.3 °F; 142.7 to 144.1 K
Boiling point 35.9 to 36.3 °C; 96.5 to 97.3 °F; 309.0 to 309.4 K
40 mg L−1 (at 20 °C)
log P 3.255
Vapor pressure 57.90 kPa (at 20.0 °C)
7.8 nmol Pa−1 kg−1
Acidity (pKa) ~45
Basicity (pKb) ~59
UV-vismax) 200 nm
1.358
Viscosity 0.240 cP (at 20 °C)
Thermochemistry
167.19 J K−1 mol−1
263.47 J K−1 mol−1
−174.1–−172.9 kJ mol−1
−3.5095–−3.5085 MJ mol−1
Hazards
Safety data sheet See: data page
GHS pictograms The flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The health hazard pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The environment pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word DANGER
H225, H304, H336, H411
P210, P261, P273, P301+310, P331
Extremely Flammable F+ Harmful Xn Dangerous for the Environment (Nature) N
R-phrases R51/53, R65, R66, R67
S-phrases (S2), S16, S29, S33
NFPA 704
4
1
0
Flash point −49.0 °C (−56.2 °F; 224.2 K)
260.0 °C (500.0 °F; 533.2 K)
Explosive limits 1.5–7.8%[2]
Lethal dose or concentration (LD, LC):
LD50 (Median dose)
  • 3 g kg−1 (dermal, rabbit)
  • 5 g kg−1 (oral, mouse)
130,000 mg/m3 (mouse, 30 min)
128,200 ppm (mouse, 37 min)
325,000 mg/m3 (mouse, 2 hr)[3]
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 1000 ppm (2950 mg/m3)[2]
REL (Recommended)
TWA 120 ppm (350 mg/m3) C 610 ppm (1800 mg/m3) [15-minute][2]
1500 ppm[2]
Related compounds
Related alkanes
Supplementary data page
Refractive index (n),
Dielectric constantr), etc.
Thermodynamic
data
Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
 Y  (: Y/N?)

Pentane is an formula C5H12 — that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the n-pentane isomer; the other two being called isopentane (methylbutane) and neopentane (dimethylpropane). Cyclopentane is not an isomer of pentane.

Pentanes are components of some fuels and are employed as specialty solvents in the laboratory. Their properties are very similar to those of butanes and hexanes.

Contents

  • Isomers 1
  • Industrial uses 2
  • Laboratory use 3
  • Physical properties 4
  • Reactions 5
  • References 6
  • External links 7

Isomers

Common name normal pentane
unbranched pentane
n-pentane
isopentane neopentane
IUPAC name pentane 2-methylbutane 2,2-dimethylpropane
Molecular
diagram
Skeletal
diagram
Melting
Point (°C)[4]
−129.8 −159.9 −16.6
Boiling
Point (°C)[4]
36.0 27.7 9.5
Density (g/l)[4] 621 616 586

Industrial uses

Pentanes are some of the primary blowing agents used in the production of polystyrene foam and other foams. Usually, a mixture of n-, i-, and increasingly cyclopentane is used for this purpose.

Because of its low boiling point, low cost, and relative safety, pentane is used as a working medium in geothermal power stations. It is added into some refrigerant blends as well.

Pentanes are also used as an active ingredient in some pesticides.[5]

Laboratory use

Pentanes are relatively inexpensive and are the most volatile alkanes that are liquid at room temperature, so they are often used in the laboratory as solvents that can be conveniently evaporated. However, because of their nonpolarity and lack of functionality, they can only dissolve non-polar and alkyl-rich compounds. Pentanes are miscible with most common nonpolar solvents such as chlorocarbons, aromatics, and ethers. They are also often used in liquid chromatography.

Physical properties

The boiling points of the pentane isomers range from about 9 to 36 °C. As is the case for other alkanes, the more branched isomers tend to have lower boiling points.

The same trend normally holds for the melting points of alkane isomers, and indeed that of isopentane is 30 °C lower than that of n-pentane. However, the melting point of neopentane, the most heavily branched of the three, is 100 °C higher than that of isopentane. The anomalously high melting point of neopentane has been attributed to the better solid-state packing assumed to be possible with its tetrahedral molecule; but this explanation has been challenged on account of it having a lower density than the other two isomers.[4]

The branched isomers are more stable (have lower heat of formation and heat of combustion) than normal pentane. The difference is 1.8 kcal/mol for isopentane, and 5 kcal/mol for neopentane.[6]

Rotation about two central single C-C bonds of n-pentane produces four different conformations.[7]

Reactions

Like other alkanes, pentanes are under standard room temperature and conditions largely unreactive - however, with sufficient activation energy (i.e. an open flame), they get readily oxidized to form carbon dioxide and water:

C5H12 + 8 O2 → 5 CO2 + 6 H2O + heat/ energy

Like other alkanes, pentanes undergo free radical chlorination:

C5H12 + Cl2 → C5H11Cl + HCl

Such reactions are unselective; with n-pentane, the result is a mixture of the 1-, 2-, and 3-chloropentanes, as well as more highly chlorinated derivatives. Other radical halogenations can also occur.

References

  1. ^ n-PentaneRecord of in the GESTIS Substance Database of the IFA, accessed on 19 April 2011
  2. ^ a b c d e "NIOSH Pocket Guide to Chemical Hazards #0486".  
  3. ^ "n-Pentane". Immediately Dangerous to Life and Health.  
  4. ^ a b c d James Wei (1999), Molecular Symmetry, Rotational Entropy, and Elevated Melting Points. Ind. Eng. Chem. Res., volume 38 issue 12, pp. 5019–5027 doi:10.1021/ie990588m
  5. ^ Milne, ed., G.W.A. (2005). Gardner's Commercially Important Chemicals: Synonyms, Trade Names, and Properties. Hoboken, New Jersey: John Wiley & Sons, Inc. p. 477.  
  6. ^ From the values listed at Standard enthalpy change of formation (data table).
  7. ^ Roman M. Balabin (2009). "Enthalpy Difference between Conformations of Normal Alkanes: Raman Spectroscopy Study of n-Pentane and n-Butane". J. Phys. Chem. A 113 (6): 1012–9.  

External links

  • International Chemical Safety Card 0534 at ILO.org
  • NIOSH Pocket Guide to Chemical Hazards at CDC.gov
  • Phytochemical data for pentane at Ars-grin.gov
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.