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Alkanes: Definition, Properties, Formula & Examples

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  • 0:01 What Are Alkanes?
  • 0:51 Types & Examples
  • 1:59 Chemical Formula & Examples
  • 4:31 Lesson Summary
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Lesson Transcript
Instructor: Nissa Garcia

Nissa has a masters degree in chemistry and has taught high school science and college level chemistry.

Alkanes are chemical compounds that play a very important role in our lives. Plastic products, gasoline, natural gas - alkanes are necessary for us to have these. In this lesson, we will learn all about alkanes.

What Are Alkanes?

Fuel is very important to us. We need fuel for our cars, to heat up our homes, and for many other things. Many substances are involved in the production of fuel, and one of the raw materials needed to make fuel is a type of chemical compounds known as an alkane.

Alkanes are chemical compounds that consist of carbon (C) and hydrogen (H) atoms, so they are also called hydrocarbons. The chemical structure of alkanes only consists of single bonds. This illustration shows examples of the chemical structures of two alkanes: ethane and pentane.

Taking a look at ethane and pentane, these alkanes are referred to as saturated because they only contain single bonds, and because of that, each carbon atom is saturated with hydrogen atoms. Alkanes are therefore referred to as saturated hydrocarbons.

Types of Alkanes and Examples

The chemical structure of alkanes has three types: linear, branched, and cyclic. In this section, we will define each type and show examples for each.

Linear alkanes have the carbons bonded together in a chain-like structure, similar to a snake. This table shows some examples of linear alkanes. Let's take a look at decane, for example. The chemical structure can be drawn two ways. It can be drawn with all the carbon and hydrogen atoms being shown, or it can be drawn as a chain (the hydrogen atoms are not shown), where each edge represents a carbon atom.

Linear Alkanes Examples

Branched alkanes are derived from linear alkanes, but instead of having just a straight chain in their chemical structure, it is branched with one or more alkyl groups. An alkyl group is a group of carbon and hydrogen atoms attached to an alkane molecule. Let's take a look at some examples of branched alkanes so we can picture them more clearly.

Branched Alkanes

We can see that the alkane chain has branches of alkyl groups.

Cyclic alkanes or cycloalkanes consist of hydrogen and carbon atoms bonded together with single bonds, where the carbon atoms bond together to form a ring or loop.

Cyclic Alkanes Examples

General Chemical Formula of Alkanes and Examples

The general formula for alkanes is:

General Chemical Formula of Alkanes

The general formula of cyclic alkanes is:

General Chemical Formula of Cyclic Alkanes

Let's take a look at a few examples of alkanes. Here, we can see that these alkanes follow the general chemical formula specified above.

Example 1: Pentane

Pentane is a linear straight chain alkane and has five carbon (C) atoms, so n = 5. We, therefore, use the general chemical formula for alkanes here CnH2(n+1).

Alkanes Example 1

Example 2: Cyclobutane

Cyclobutane is a cyclic alkane, and it has four carbon (C) atoms, so n = 4. The four carbon atoms are bonded to each other, making one ring. Here, we use the general formula for cyclic alkanes CnH2(n+1-g). Cyclobutane can be drawn two ways: on the left, we see that it shows all the carbon and hydrogen atoms, and on the right, cyclobutane can be drawn as a square, where the hydrogen atoms are not shown, and each edge of the square represents carbon atoms. In the chemical structure, we have a ring, so g = 1.

Alkanes Example 2

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