Hydrocarbons · 8 min read
Alkanes
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Introduction to Alkanes
Imagine your mother cooking at home with a gas cylinder or a kerosene stove. The fuel inside that cylinder is mostly made of Alkanes. Alkanes are the simplest family of organic compounds made of only carbon and hydrogen.
In simple terms, they are chemicals containing only carbon and hydrogen where every carbon atom is joined to others by single lines or bonds.
The Concept of Saturation
When we say a compound is saturated, it means it has no room to take in more atoms. It is like a 'danfo' bus that is already full of passengers; nobody else can enter unless someone leaves. In Alkanes, all the bonds around the carbon atoms are single bonds.
This means the carbon atoms are 'full' and cannot form more bonds with new atoms.
Homologous Series of Alkanes
Alkanes belong to a family called a homologous series. Members of this family look alike and behave similarly. The first member is Methane (CH4), followed by Ethane (C2H6), Propane (C3H8), and Butane (C4H_{10}).
Basically, each member differs from the next one by just one carbon and two hydrogens, which is a CH2 group.
Physical and Chemical Properties
Small alkanes like methane are gases (used for cooking), medium ones are liquids (like petrol), and very large ones are solids (like candle wax). They do not dissolve in water, just like how oil will float on top of your soup.
Because they are 'full' or saturated, they are not very reactive. Their main reaction is Substitution, where one atom is kicked out and replaced by another, like a football coach making a substitution during a match.
Naming Alkanes (IUPAC System)
To name them, we count the longest chain of carbon atoms. 1 carbon is Meth-, 2 is Eth-, 3 is Prop-, and 4 is But-. We then add '-ane' at the end. For example, a 5-carbon chain is called Pentane.
Worked Example: Finding a Formula
Let us find the formula for an Alkane that has 6 carbon atoms (Hexane).
1. Start with the general formula: Cn H2n+2.
2. Since it has 6 carbons, n = 6.
3. Calculate the number of hydrogens: (2 x 6) + 2 = 12 + 2 = 14.
4. Therefore, the formula for Hexane is C6H_{14}.
Key points
- •Alkanes are saturated hydrocarbons with single bonds only.
- •The general formula for the alkane family is Cn H2n+2.
- •They undergo substitution reactions especially with halogens like Chlorine.
- •Methane (CH4) is the simplest alkane and the main part of natural gas.
- •Members of the series differ by a CH2 group and have a 14g molar mass difference.