Heptane

From Wikipedia, the free encyclopedia
Heptane
IUPAC name

Heptane[1]

Identifiers
CAS number 142-82-5 YesY
PubChem 8900
ChemSpider 8560 YesY
UNII 456148SDMJ YesY
EC number 205-563-8
UN number 1206
MeSH n-heptane
ChEBI CHEBI:43098 YesY
ChEMBL CHEMBL134658 YesY
RTECS number MI7700000
Beilstein Reference 1730763
Gmelin Reference 49760
Jmol-3D images Image 1
Properties
Molecular formula C7H16
Molar mass 100.20 g mol−1
Appearance Colourless liquid
Odor Petrolic
Density 0.6795 g mL−1
Melting point −91.0 to −90.1 °C; −131.7 to −130.3 °F; 182.2 to 183.0 K
Boiling point 98.1 to 98.7 °C; 208.5 to 209.6 °F; 371.2 to 371.8 K
log P 4.274
Vapor pressure 5.33 kPa (at 20.0 °C)
kH 12 nmol Pa−1 kg−1
Refractive index (nD) 1.387
Viscosity 386 μPa s
Dipole moment 0.0 D
Thermochemistry
Std enthalpy of
formation ΔfHo298		 −225.2–−223.6 kJ mol−1
Std enthalpy of
combustion ΔcHo298		 −4.825–−4.809 MJ mol−1
Standard molar
entropy So298		 328.57 J K−1 mol−1
Specific heat capacity, C 224.64 J K−1 mol−1
Hazards
GHS pictograms
GHS signal word DANGER
GHS hazard statements H225, H304, H315, H336, H410
GHS precautionary statements P210, P261, P273, P301+310, P331
EU Index 601-008-00-2
EU classification F Xn N
R-phrases R11, R38, R50/53, R65, R67
S-phrases (S2), S16, S29, S33
NFPA 704
3
1
0
Flash point −4.0 °C; 24.8 °F; 269.1 K
Autoignition temperature 223.0 °C; 433.4 °F; 496.1 K
Explosive limits 1.05–6.7%
Related compounds
Related alkanes
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

n-Heptane is the straight-chain alkane with the chemical formula H3C(CH2)5CH3 or C7H16. When used as a test fuel component in anti-knock test engines, a 100% heptane fuel is the zero point of the octane rating scale (the 100 point is a 100% iso-octane). Octane number equates to the anti-knock qualities of a comparison mixture of heptane and isooctane which is expressed as the percentage of isooctane in heptane and is listed on pumps for gasoline dispensed in the United States and internationally.

Uses

Heptane (and its many isomers) is widely applied in laboratories as a totally non-polar solvent. As a liquid, it is ideal for transport and storage. In the grease spot test, heptane is used to dissolve the oil spot to show the previous presence of organic compounds on a stained paper. This is done by shaking the stained paper in a heptane solution for about half a minute.[citation needed]

Aqueous bromine may be distinguished from aqueous iodine by its appearance after extraction into heptane. In water, both bromine and iodine appear brown. However, iodine turns purple when dissolved in heptane, whereas the bromine solution remains brown.

Heptane is commercially available as mixed isomers for use in paints and coatings, as the rubber cement solvent "Bestine", the outdoor stove fuel "Powerfuel" by Primus, as pure n-Heptane for research and development and pharmaceutical manufacturing and as a minor component of gasoline.

Octane rating scale

n-Heptane is the zero point of the octane rating scale. It is undesirable in petrol, because it burns explosively, causing engine knocking, as opposed to branched-chain octane isomers, which burn more slowly and give better performance. It was chosen as the zero point of the scale because of the availability of very high purity n-heptane, unmixed with other isomers of heptane or other alkanes, distilled from the resin of Jeffrey Pine and from the fruit of Pittosporum resiniferum. Other sources of heptane and octane, produced from crude oil, contain a mixture of different isomers with greatly differing ratings and do not give as precise a zero point. ChevronPhillips Specialty Chemical produces a specialized grade of high purity n-Heptane (>99.0%) from crude oil through precision refining and distillation that is used in the measurement of octane rating for fuels.

Isomers and enantiomers

Heptane has nine isomers, or eleven if enantiomers are counted:

  • Heptane (n-heptane), H3C–CH2–CH2–CH2–CH2–CH2–CH3,
  • 2-Methylhexane (isoheptane), H3C–CH(CH3)–CH2–CH2–CH2–CH3,
  • 3-Methylhexane, H3C–CH2–C*H(CH3)–CH2–CH2–CH3 (chiral),
  • 2,2-Dimethylpentane, (H3C)3–C–CH2–CH2–CH3,
  • 2,3-Dimethylpentane, (H3C)2–CH–C*H(CH3)–CH2–CH3 (chiral),
  • 2,4-Dimethylpentane, (H3C)2–CH–CH2–CH–(CH3)2,
  • 3,3-Dimethylpentane, H3C–CH2–C(CH3)2–CH2–CH3,
  • 3-Ethylpentane, H3C–CH2–CH(CH2CH3)–CH2–CH3,
  • 2,2,3-Trimethylbutane, CH3–C(CH3)2–CH(CH3)–CH3, this isomer is also known as pentamethylethane and triptane.[2]

References

  1. ↑ "n-heptane – Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and Related Records. Retrieved 2 January 2012. 
  2. ↑ Isomers. Members.optushome.com.au. Retrieved on 2012-03-04.

External links

This article is issued from Wikipedia. The text is available under the Creative Commons Attribution/Share Alike; additional terms may apply for the media files.