Alcohols 4.2.1 Flashcards
Define functional group
A group of atoms that determines the substances chemical properties.
What is the general formula for alcohols (aliphatic alcohols with one OH group only)
CnH(2n+2)O
What are phenols?
Aromatic alcohols, they have an alcohol group directly attached directly to the benzene ring.
What are the two possibles names that you can use for alcohols when naming them? When would you use each?
‘Ol’- when it is the only functional group eg. Butan-1-ol (suffix)
‘Hydroxy’ - when there is another function group eg. 2-Hydroxy propanoic acid. (Prefix)
What are the five main uses for alcohols?
- Solvents
- Petrol additive to improve combustion
- Feedstock - in the production of other organic chemicals
- Drinks
- Fuels - alcohols have high enthalpies of combustion
Why can alcohols make hydrogen bonds?
Alcohols can make hydrogen bonds with water molecules and with each other because they have H bonded to an electronegative O.
How do hydrogen bonds affect volatility?
They reduce volatility.
What is volatility?
How easy it is to turn something from a liquid to a gas
Why type of IMF is most often present between ethanol molecules?
Hydrogen bonding
Why might ethanol have a higher boiling point than ethane?
Ethane has induced dipole dipole forces which are the weakest type of IMF whereas ethanol has hydrogen bonding which is the strongest type of IMF. So more energy is required to break the IMF in ethanol.
Why does an increase in chain length affect the boiling point? What effect does it have to the boiling point?
An increase in chain length means that there is an increase in the number of electrons and surface contact so there are more induced dipole dipole forces making it stronger and therefore more energy is required to break them.
Why are alcohols soluble?
Alcohols have a tendency to be water soluble because they can form hydrogen bonds with water.
How does chain length affect solubility?
Solubility decreases as the hydrocarbon chain increases in size, as the OH group has less influence and the solubility of the longer hydrocarbon chain becomes more dominant.
Which molecule would you expect to be more soluble; ethan-1,2-diol or ethanol? Why?
Ethan-1,2-diol as it has more OH groups so it will therefore require twice as much energy to break the hydrogen bonds. (Twice as many H bonds due to another OH group).
Match up the following alcohols with their solubility:
C8H18O Completely miscible
Butanol 9.00
Methanol 0.0540
C5H12O. 0.600
1C
2B
3A
4D
