Heptane

Brief Overview

Heptane is an alkane with the chemical formula C₇H₁₆. It is a hydrocarbon and can undergo combustion which gives off energy in the form of heat: C₇H₁₆ + 11O₂ → 7CO₂ + 8H₂O. This reaction is an exothermic reaction. Heptane is used as a solvent, as a component in gasoline, and to set the standard zero point for gasoline octane rating. It is a clear, colorless liquid with a gasoline-like odour and is highly flammable.

Manufacturing Process

Fractional distillation of petroleum would yield heptane which can then be purified by rectification. Heptane can also be produced in a three-step chemical reaction. Purified 2-heptanone first undergo catalytic reduction to 2-heptanol which is then dehydrated to a mixture of n-heptenes. Hydrogenation of these heptenes would eventually yield n-heptane.

Gasoline Industry

n-Heptane is used as the zero point of the octane rating scale. It is undesirable in petrol, because it burns explosively which causes engine knocking, as opposed to branched-chain octane isomers, which burn slower and give better performance. Heptane was chosen as the zero point of the scale because of the availability of very high purity n-heptane that is free from isomers and hence gives a precise zero point.

Solvent Industry

Heptane is widely used in laboratories as a non-polar solvent. It exists as a liquid and is hence ideal for transport and storage. Heptane is also used in the grease spot test, where it is used to dissolve the oil spot to show the previous presence of organic compounds on a stained paper.