Definition
A Hydrocarbon is a molecule is ONLY hydrogen and carbon. This means that they are Simple Covalent molecules
Name Scheme
Hydrocarbons are named based on the number of carbon atoms they have and then the type of molecule they are.
Number of C atoms | Prefix |
---|---|
1 | Meth- |
2 | Eth- |
3 | But- |
4 | Prop- |
5 | Pent |
6 | Hex- |
7 | Hept- |
8 | Oct- |
Types of Hydrocarbons
Alkanes
Name Scheme - Prefix + -ane
They have general formula
Alkenes
Name Scheme - Prefix + -ene
They have general formula
Alcohols
Name Scheme - Prefix + -anol
They have general formula
Carboxylic Acid
Name Scheme - Prefix + -anoic + Acid
They have general formula
Short vs Long Chain Hydrocarbons
Short Chain Hydrocarbons have WEAKER intermolecular forces as there is less atoms - this is the reason for many of the differences so if you remember this you can figure out the rest with common sense
Property | Short-Chain Hydrocarbons | Long-Chain Hydrocarbons |
---|---|---|
Number of Carbon Atoms | Few (e.g., C1-C4) | Many (e.g., C15+) |
Boiling Point | Low | High |
Viscosity (thickness) | Low (runny) | High (thick) |
Flammability | High (burns easily) | Low (hard to ignite) |
Volatility (how easily it evaporates) | High | Low |
Smokiness of Flame | Clean flame | Smoky flame |
Uses | Fuels (e.g., LPG, petrol) | Lubricants, bitumen (road surfacing) |
Fractional Distillation Location | Collected at the top (cooler) | Collected at the bottom (hotter) |
Cracking Needed? | No | Yes (to make useful short-chain hydrocarbons) |
Key Points:
- Short-chain hydrocarbons are more useful as fuels because they ignite easily and burn with a clean flame.
- Long-chain hydrocarbons are broken down by cracking to produce more useful, smaller molecules.
- Fractional distillation is used to separate different hydrocarbons based on their boiling points.
Uses of Hydrocarbons
Combustion Of Hydrocarbons
Complete
Fuel + Oxygen
Incomplete
Fuel + Oxygen (Not Enough)
Esters
An ester is an organic compound formed by a Carboxylic Acid and Alcohol.
It has general formula
Reactions
Alkenes
Hydrogenation
The double carbon bond opens up to form 2 single bonds for hydrogen
Alkene + Bromine Water
The bromine goes from orange to colourless. This means it is a good test for Alkene presence
Alkene + Halogen
It is an Addition Reaction as the double bond opens up forming 2 single bonds for the Halogen so only one molecule is produce. Effectively the halogen is just added on hence the name. Similar to Alkene + Hydrogen
Example
Hydration of Alkene
Requires temperature of 360
Alcohols
Oxidation
Alcohol + Oxidation Agent
Combustion
Fermentation of Sugar
Requires temperatures of 30
Carboxylic Acid
How to name salt Metal + alkane name + -oate
Carboxylic Acid + Metal
Carboxylic Acid + Metal
Example
Carboxylic Acid + Carbonate
Carboxylic Acid + Carbonate
Example
Carboxylic Acid + Alkali
Carboxylic Acid + Alkali
Example
Making Esters
Carboxylic Acid + Alcohol
Example