In I/GCSE Chemistry, we will learn about the alcohols.
Alcohols have similar properties b/c they have the OH at the end.
The formula CnH (2n+1) OH, where n = no of carbon atoms, can be used to determine the formula for each alcohol.
Alcohol (contains hydrocarbons) + burning --> Carbon dioxide + water
Properties
- Good solvent – Can dissolve in compounds that water can’t
- Soluble in water
- Liquid at room temp. – evaporate + volatile (give of fumes).
- Intermolecular forces are stronger with the–OH functional group; other molecules can join to the alcohol easily.
- Flammable – catches a clean flame.
- b/c it is pure, can be used as fuel
- High boiling point
An alcohol can become a water molecule or an alkane when you replace the – H atom.
Alcohols are liquids whereas Alkanes are gasses. This shows that attractive forces between alcohol molecules (intermolecular) are stronger than the forces in Alkanes.
This is b/c the – OH group gives the molecules a greater tendency to cling together – like water.
The C – O + O – H are more reactive than the C – C + C – H in Alkanes.
However, ethanol boiling point is lower than water. This is because ethanol molecules have a greater mass than water molecules BUT the attraction between the hydrocarbon parts is weak.
Ethanol molecules have more tendencies to stick to each other than Alkanes but fewer tendencies to stick to each other compared to water.
B/c the – OH group allows other molecules to cling together; alcohol and water can mix together.
- But if hydrocarbon length is too long the oiliness of the alcohol will dominate and it will be too difficult to mix.
Reaction with sodium
Only the hydrogen atom in the – OH is involved in the reaction. The hydrogen atoms linked to the carbon
(C –H) are inert or un-reactive.
These two reactions with sodium are similar b/c the ethanol + water both have the – OH group.
Na + H2O --> NaOH + H2 (+ squeaky pop)
Na + C2H5OH --> NaO + H2
An ionic bond is formed between the positive sodium and negative oxygen.
E.g. 2C2H5OH + Na --> 2C2H5ONa
You got it now!
