Difference Between Hexane and Cyclohexane

Main Difference – Hexane vs Cyclohexane

Hexane and cyclohexane are both alkanes with six carbon atoms each. However, the main difference between Hexane and Cyclohexane lies in their molecular structure. Hexane has a linear carbon chain whereas cyclohexane is a cyclic molecule. Due to the cyclic arrangement in its molecular structure, cyclohexane possesses a lesser number of hydrogen atoms compared to hexane. Due to these structural differences, both hexane and cyclohexane own unique properties.

This article studies,
1. What is Hexane
      – Definition, Molecular Structure, Properties, Uses
2. What is Cyclohexane
      – Definition, Molecular Structure, Properties, Uses
3. What is the difference between Hexane and Cyclohexane

What is Hexane

The molecular formula of hexane, which consists of 6 carbon atoms and 14 hydrogen atoms, is C₆H₁₄. All the bonds that connect carbons are single bonds. Hence, hexane is an alkane and is unbranched. The molecular weight of hexane is 86.178 g/mol.

Hexane, which is called n-hexane as well, is a colorless liquid that is often used as an organic solvent. It has a similar odor to petroleum. Hexane boils at 68.7 ̊C and freezes at -95.3 ̊C. Furthermore, it is highly flammable and has a relatively high vapor pressure, due to which it is highly volatile.

Hexane is a non-polar solvent and does not mix up with water. However, it is soluble in other organic solvents such as alcohol, ether, chloroform and acetone. This is abundantly used in extracting plant oils. As plant oils are non-polar, they readily dissolve in hexane. Moreover, it is used as a cleaning solvent and a degreasing agent in various industries.

Figure 1: Molecular Structure of Hexane

Hexane is a part of crude oil paraffin fraction and natural gas, which is separated at 65-70 ̊C during crude oil refining. It is emitted by combusting polyvinyl chloride. Human exposure is mainly due to dermal contact or inhalation. Acute exposure may cause eye irritation, central nervous system depression and symptoms are nausea, headache, giddiness, and dizziness. Chronic exposure may result in polyneuropathy with numbness, muscular weakness, blurred vision, fatigue and headache in extreme conditions. Hexane is not reported to be carcinogenic.

What is Cyclic Cyclohexane

As the name implies, cyclohexane is a cyclic alkane. It does not have any multiple bonds within. The molecular weight of cyclohexane is 84.162 g/mol. It has 2 hydrogen atoms less compared to hexane and the molecular formula is C₆H₁₂. The boiling point of cyclohexane is 80.74 ̊C whereas the freezing point is 6.55  ̊C.

Cyclohexane, similarly to hexane, is a non-polar solvent and does not dissolve water. It is used as a solvent to dissolve substances such as fats, oils, waxes, lacquers, resins and cellulose ethers. Cyclohexane is often used in perfume manufacturing, for the production of adipic acid in nylon 66 manufacturing, paint and varnish industry etc.

Figure 2: Cyclohexane Structure

Cyclohexane is a non-corrosive and flammable liquid. It is a mild eye irritant, but inhalation of large quantities can cause central nervous system impairment. This may give rise to symptoms such as headaches, anesthesia, and convulsions. Cyclohexane is mainly released to the environment as a byproduct of various industries. It is a helping factor for the formation of photochemical smog.

Difference Between Hexane and Cyclohexane

Molecular Formula

Hexane: Molecular formula is C₆H₁₄

Cyclohexane: Molecular formula is C₆H₁₂

Molecular Weight

Hexane: Molecular weight is 86.178 g/mol

Cyclohexane: Molecular weight is 84.162 g/mol

Freezing Points

Hexane: Freezing point is -95.3  ̊C

Cyclohexane: Freezing point is 6.55  ̊C

Boiling Point 

Hexane: Boiling point is 68.7  ̊C

Cyclohexane: Boiling point is 80.74 ̊C

Intermolecular Attractions

Hexane: Hexane is comparatively less strong.

Cyclohexane: Cyclohexane is comparatively stronger.

Health Hazards

Hexane: Hexane is more hazardous.

Cyclohexane: Cyclohexane is less hazardous.

Uses 

Hexane: Hexane is used as a cleaning solvent and a degreasing agent.

Cyclohexane: Cyclohexane is used for paint, varnish and nylon manufacture.

Conclusion

The main difference between hexane and cyclohexane lies in their structural arrangement. Hexane is linear while cyclohexane is cyclic. Furthermore, hexane has a bit higher molecular weight than cyclohexane. This is due to the fact that cyclohexane has 2 hydrogens less compared to hexane.

The volume cyclohexane occupies is lower than hexane due to its cyclic structure. Hence, there’s a higher number of cyclohexane molecules in a given molecule when compared with hexane. The Van Der Waals forces between molecules are inversely proportional to the distance between molecules. Since cyclohexane molecules are closely packed, the molecular interactions are much stronger than that of hexane. Therefore, the energy required to break the bonds and evaporate it is much higher. Hence, cyclohexane has a higher boiling point. There is a vast gap between their freezing points as well. Cyclohexane is easily condensed due to its stronger molecular interactions.

Hexane and cyclohexane have a lot of similarities. They appear same to the eye and has a similar odor. Both are flammable. However, they have the different properties discussed above due to their structural difference.

Reference:
1.”Hexane Solvent Properties.” Macromolecular Studies Group. Louisiana State University, n.d. Web. 15 Feb. 2017.
2.”HEXANE.” Scorecard Home. N.p., n.d. Web. 15 Feb. 2017.
“3.HEXANE | C6H14 – PubChem.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 15 Feb. 2017.
4.”CYCLOHEXANE | C6H12 – PubChem.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 15 Feb. 2017.

Image Courtesy:
1.”Hexane displayed”By Calvero. – Selfmade with ChemDraw. (Public Domain) via Commons Wikimedia
2.”Cyclohexane for high school” By すじにくシチュー – Own work (CC0) via Commons Wikimedia