Organic Chemistry
Organic chemistry is mainly based around hydrocarbons – compounds made only up of hydrogen and carbon. It is drawn with lines joining carbons and hydrogen. All carbon bonds have to be bonded to hydrogen – if not something else. The left picture below shows carbons with all bonds taken up (ethane). The right picture below shows an incorrect picture of a hydrocarbon because one of the carbons has a free bond.
- Hydrocarbon – compounds that contain carbon and hydrogen only.
- Homologous series – family of compounds with similar properties because they have similar bonding. They show a graduation in physical properties (mpt/bpt) and similar chemical properties such as the general formula. Alkanes are the simplest.
- Saturated – when carbon cannot take anymore bonds – single carbon-carbon bonds.
- Unsaturated – presence of a carbon-carbon double bond.
- General formula – The formula of different homologous series of carbons.
- Isomers – molecules with the same molecular formula but different structural
Learning the Code
| Code | Number of Carbons |
| Meth | 1 |
| Eth | 2 |
| Prop | 3 |
| But | 4 |
| Pent | 5 |
| Hex | 6 |
| Hept | 7 |
| Oct | 8 |
| Non | 9 |
| Dec | 10 |
Do you have to remember the formula for propane, butane, ethane…? No! You can work it out yourself! The first part of the name tells you how many carbons there are in the longest chain (not necessarily in total). By the way you have to learn these – at least the first five. It helps.
For example: propane (left) has three carbons. Butane (right) has four carbons.
Alkanes and Alkenes
| Ending | Meaning? |
| ‘ane’ | All carbon bonds are filled with hydrogen – i.e. they are saturated hydrocarbons. |
| ‘ene’ | There is a double carbon-carbon bond – they are unsaturated hydrocarbons. |
Alkanes and Alkenes are two homologous series.
Pentene has a five carbon chain with a double bond.
