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Carbon has four valence electrons, so it can form four covalent bonds.
Carbon can bond to other carbon atoms, making chains and molecules with different shapes.
Organic chemistry is the study of carbon compounds.
This chapter focuses on hydrocarbons, which are compounds made only of carbon and hydrogen.

Crude oil formed from ancient plants, animals, and microorganisms that were buried, then changed by heat and pressure over millions of years.
Crude oil is less dense than water and can move upward through rock until it is trapped under impervious rock, forming an oil field.
Crude oil is separated in refineries by fractional distillation.
Fractional distillation separates crude oil into fractions with similar boiling points and similar molecular masses.
Most crude oil fractions are used as fuels.
Main fractions shown in the diagram:
- Petroleum gas: about C1-C4, used as gaseous fuels for cooking and heating.
- Naphtha: about C5-C9, used as a petrochemical feedstock.
- Gasoline: about C5-C12, used as motor fuel.
- Kerosene: about C10-C16, used for jet engines and kerosene heaters.
- Diesel gas oil: about C14-C20, used as diesel oil, furnace oil, and petrochemical feedstock.
- Heavy gas oil/lubricating oils: about C16-C25, used for lubricating oils and as cracking stock.
- Paraffin waxes and residues: larger molecules, used in candles, cosmetics, polishes, asphalt, and tar.

Alkanes are hydrocarbons that contain only single covalent bonds.
Because they only have single bonds, alkanes are called saturated molecules.
Alkanes belong to a homologous series, where each member differs from the previous one by a −CH2−−CH2− unit.
Members of the same homologous series have similar structures, similar chemical properties, and the same general formula.
The general formula for alkanes is CnH2n+2CnH2n+2.
Alkanes are non-polar, so the forces between molecules are weak, giving them relatively low melting and boiling points.
As alkane molecules get larger, melting and boiling points increase.
Examples:
- Methane: CH4, colourless and odourless, and the main component of natural gas.
- Ethane: C2H6.
- Propane: C3H8.
- Octane: C8H18.
- Dodecane: C12H26.

Alkanes can be shown using molecular formulae, Lewis/electron-dot diagrams, condensed structural formulae, and structural formulae.
A condensed structural formula shows the atom groups in order, while a structural formula shows all the bonds.
Structural isomers have the same molecular formula but different arrangements of atoms.
Methane, ethane, and propane each have only one possible structure, but butane has two structural isomers.
The two butane isomers shown are straight-chain butane and branched butane.
A side chain such as −CH3−CH3 is called a methyl group, and −CH2CH3−CH2CH3 is called an ethyl group.
The alkyl group names shown are methyl, ethyl, propyl, butyl, and pentyl.
Important trend:
- Isomers can have different physical properties even though they have the same molecular formula.
- The hexane isomers shown have different melting and boiling points because molecular shape affects intermolecular forces.

Alkane names end in -ane.
The stem tells you the number of carbon atoms: meth-, eth-, prop-, but-, pent-, hex-, hept-, oct-, non-, dec-.
IUPAC naming steps:
1. Find the longest unbranched carbon chain.
2. Count the carbon atoms in that chain to get the parent name.
3. Number the chain from the end nearest the first branch.
4. Identify the side chain(s), such as methyl or ethyl.
5. Give the position number of each branch.
6. Use prefixes like di- or tri- for identical side chains.
7. Put different side chains in alphabetical order.
Example from the chapter:
- A five-carbon main chain is pentane.
- A methyl group on carbon 2 gives the name 2-methylpentane.
- Names such as 3-methylpentane, 3,3-dimethylpentane, and 2,3-dimethylbutane show how position numbers and prefixes are used.

Alkane = saturated hydrocarbon with only single bonds.
General formula of alkanes = CnH2n+2CnH2n+2.
More carbon atoms usually means a higher boiling point.
Isomers have the same formula but different structures.
To name an alkane, find the longest chain first, then number from the nearest branch.

Chapter 8.2 Pearson

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond.
Because of the double bond, alkenes are unsaturated hydrocarbons.
Alkenes are a homologous series.
The general formula for alkenes with one double bond is CnH2nCnH2n.
Alkenes are more reactive than alkanes because they contain a carbon-carbon double bond.

The simplest alkene is ethene, C2H4.
The next members shown are propene, C3H6, and butene, C4H8.
The names of alkenes end in -ene.
The double bond affects the shape of the molecule, and the bond angle around the double bond is about 120 degrees.
Alkenes are non-polar and do not dissolve in water.
Uses shown in the table:
- Ethene is used in the manufacture of a wide range of chemicals.
- Propene is used to make propene oxide and polymers.
- Butene is used in the manufacture of butanol and polymers.

Alkenes can be represented using molecular formulae, electron-dot/Lewis structures, condensed structural formulae, and structural formulae.
For ethene, the condensed structural formula is CH2CH2 with a double bond between the carbons shown in the structural formula.
For propene, the condensed structural formula is CH2CHCH3, again with a double bond shown in the full structure.

Alkenes with more than three carbon atoms can form structural isomers.
These isomers can differ because the carbon chain is arranged differently or because the double bond is in a different position.
The butene examples shown are but-1-ene, but-2-ene, and methylpropene.
When naming alkene isomers, the carbon chain is numbered from the end nearest the double bond so the double bond gets the lowest possible number.

Some alkenes show cis-trans isomerism, also called geometric isomerism.
This happens because atoms joined by a carbon-carbon double bond cannot freely rotate.
In a cis isomer, the same groups are on the same side of the double bond.
In a trans isomer, the same groups are on opposite sides of the double bond.
The example shown is but-2-ene, which can exist as cis-but-2-ene and trans-but-2-ene.

To name an alkene, first find the longest carbon chain that contains the double bond.
Number the chain from the end nearest the double bond.
Name the alkyl side groups attached to the chain.
Show the position of the double bond by the number of the first carbon in the double bond, such as hex-2-ene.
Show the position of each alkyl group at the front of the name.
If there is more than one identical side chain, use prefixes such as di- or tri-.
If the molecule has geometric isomerism, include whether it is cis or trans.
Example from the chapter:
1. Identify the longest chain containing the double bond.
2. Number from the end closest to the double bond.
3. Identify the methyl branch and its position.
4. The full name becomes 4-methylpent-2-ene.
5. Because the groups are on opposite sides of the double bond, it is trans-4-methylpent-2-ene.