Alkanes – Types & Uses : Detailed Study

Alkanes 

The organic compounds having single-bonded carbon and hydrogen atoms are called alkanes. They have a homologous formula of CnH2n+2. It is further divided into chain alkanes, cycloalkanes, or branched alkanes. They have single covalent bonds in their structure.

Alkanes are the simplest form of hydrocarbons with only carbon and hydrogen atoms. The simplest form has each carbon forming four different bonds with four hydrogen atoms. The simplest alkane is methane which is written as CH₄. The longest one is an octane with 8 carbon atoms with a molecular formula of C₈H₁₈. This will be common for several alkanes but they differ in their physical, chemical, and toxicological properties.

Alkane Examples

Examples of alkane include methane, ethane, propane, butane, pentane having one, two, three, four, and five carbons each. All of these have an unbranched structure. Their respective molecular formulas are,

• Methane-CH₄
• Ethane – C₂H₆
• Propane – C₃H₈
• Butane – C₄H₁₀
• Pentane- C₅H₁₂

Physical Properties of Alkanes

The Solubility of Alkanes

Carbon and hydrogen have very little electronegativity difference between them. The covalent bonds that are formed between them or between carbon atoms are non-polar. Thus alkanes are usually non-polar compounds.

Non-polar compounds are usually soluble only in non-polar solvents, since alkanes are nonpolar, they are insoluble in water. But they are generally soluble in other solvents. 

The Boiling Point of Alkanes

Since the intermolecular Van Der Waals force is directly proportional to molecular size and the surface area, we can see that the boiling point also increases in the same manner. Alkanes have a higher boiling point, especially the single-chain alkanes when compared to their isomers. 

The Melting Point of Alkanes

The melting point of alkanes is also the same as their boiling point and increases with the molecular weight. The higher alkanes which are solid in nature, cannot overcome the intermolecular forces happening between them. So they are not easy to melt. Alkanes with even-numbered alkanes are more difficult to melt than odd-numbered ones. The former ones will have better packing of the components making it difficult to break them. 

Halogenated Alkanes

Halogenated alkanes will have one of their hydrogen atoms replaced by a halogen group element. The replaced hydrogen atom will form a halogen hydride. This is an example of a substitution reaction. The resultant product is called a haloalkane.  

For example, methane and chlorine react under heat to form chloromethane and HCl. 

Halogenation of alkane requires the assistance of external factors such as heat or UV light. Here, the heat breaks a carbon-hydrogen bond to replace it with a halogen. 

Use of Alkanes

• Alkanes are the principal component in lubricants or oils.
• Methane and ethane are natural gasses used for cooking.
• The crude oil mainly consists of alkanes.
• Alkanes with a high number of carbon atoms are used as anti-corrosive agents. 
• Alkanes such as nonane and hexadecane are used in diesel, kerosene, aviation fuel etc. 
• Alkanes having 6-8 carbon atoms are volatile and are used as solvents for nonpolar solutions. 
• Propane and butane are used as liquified gas.