Supriya Ghosh (Editor)

Heptane

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Appearance
  
Colourless liquid

Formula
  
C7H16

Density
  
684 kg/m³

Related alkanes
  
HexaneOctane

Boiling point
  
98.42 °C

Molar mass
  
100.21 g/mol

Heptane httpsuploadwikimediaorgwikipediacommons11

Heptane c7h16 lewis dot structure


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 (petrol) dispensed globally.

Contents

Heptane Illustrated Glossary of Organic Chemistry Heptane

Isomers of heptane


Uses

Heptane Heptane Energy Education

Heptane (and its many isomers) is widely applied in laboratories as a non-polar solvent. As a liquid, it is ideal for transport and storage. In the grease spot test, heptane is used to dissolve an 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.

Heptane nHeptane CAS 142825 104379

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 Illustrated Glossary of Organic Chemistry Heptane

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

Heptane FileHeptane2Dskeletalpng Wikimedia Commons

n-Heptane is defined as the zero point of the octane rating scale. It is undesirable in gasoline, because it burns explosively, causing engine knocking, as opposed to branched-chain octane isomers, which burn more slowly and give better performance. It was originally 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.

Isomers and enantiomers

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

Heptane FileHeptanesvg Wikimedia Commons

  • 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 (neoheptane), H3C–C(CH3)2–CH2–CH2–CH3,
  • 2,3-Dimethylpentane, H3C–CH(CH3)–C*H(CH3)–CH2–CH3 (chiral),
  • 2,4-Dimethylpentane, H3C–CH(CH3)–CH2–CH(CH3)–CH3,
  • 3,3-Dimethylpentane, H3C–CH2–C(CH3)2–CH2–CH3,
  • 3-Ethylpentane, H3C–CH2–CH(CH2CH3)–CH2–CH3,
  • 2,2,3-Trimethylbutane, H3C–C(CH3)2–CH(CH3)–CH3, this isomer is also known as pentamethylethane and triptane.

    • Health risks

    Acute exposure to heptane vapors can cause dizziness, stupor, incoordination, loss of appetite, nausea, dermatitis, chemical pneumonitis, or unconsciousness.

    References

    Heptane Wikipedia
    (Text) CC BY-SA