1. Introduction to Hydrocarbons Alkanes
Organic Chemistry
Introduction to
Hydrocarbons
Alkanes

2. What is Organic Chemistry
This is the branch of chemistry describing the structure and behaviors of compounds composed primarily of the elements Carbon and Hydrogen.
Just like general chemistry, there are a number of classes of compounds within this branch of the field.
Hydrocarbons are simply one of those groups of classes.

3. Hydrocarbons
This group of compounds within the field of Organic Chemistry consists of compounds containing ONLY carbon and hydrogen.
There are three separate classes of hydrocarbons – the bonding between the carbon atoms differentiates the classes.

4. Alkanes
These are hydrocarbons that have only single bonds between the carbon atoms.
The carbon atoms are all in sp3 hybrids.
These alkanes can be identified by the ratio of carbons to hydrogens.
That ratio is best described as CnH(2n+2)
Examples include the formulas
CH4
C2H6
C3H8
C4H10
Notice how each of the formulas has the correct ratio of atoms of each element.

5. Drawing Alkanes
Remember that the Carbon atoms will be in sp3 hybrids and therefore, each carbon atom will form 4 bonds.
If there is more than one carbon atom, start by connecting them in a chain.
Then add the Hydrogen atoms on the outside of that carbon “backbone”.

6. Alkane Example H H H H C C C H H H H
Remember that since all of the carbon atoms are in sp3 hybrids, the bond angles between all of the atoms is actually degrees. The molecule is not “flat” as it is drawn, but is instead a “zig-zag” shape.

7. Naming Alkanes
The key to naming these compounds is to learn the prefixes that correspond to the number of carbon atoms in the formula.
All that has to be added is the suffix “-ane” because the compound is an alkane.
C = meth
C2 = eth
C3 = prop
C4 = but
C5 = pent
C6 = hex
C7 = hept
C8 = oct
C9 = non
C10 = dec

8. Therefore: CH4 = methane C2H6 = ethane C3H8 = propane C4H10 = butane
C5H12 = pentane
C6H14 = hexane
C7H16 = heptane
C8H18 = octane
C9H20 = nonane
C10H22 = decane
Notice how each of these compounds has the described ratio of Carbon atoms to Hydrogen atoms