Alcohols Flashcards
What is the functional group of an alcohol?
What is their general formula?
OH
CnH2n+1 OH
What is a primary secondary and tertiary alcohol?
Primary alcohol:
1 alkyl group attached to the carbon with the OH group
Secondary alcohol:
2 alkyl groups attached to the carbon with the OH group
Tertiary alcohol:
3 alkyl groups attached to the carbon with the OH group
What is the trend in boiling points of alcohols?
As the alcohol chain length increases
The molecules are longer
So they have a larger surface area
Great abundance of van der waals forces of attraction between the molecules
Also form intermolecular hydrogen bonds due to the OH group.
More energy is required to overcome forces and so boiling point increases
Explain the solubility properties of alcohols?
Alcohols are soluble in polar solvents since the OH group is polar.
Alcohols can form hydrogen bonds with water molecules making them soluble in water.
What is the order of boiling points between alkenes aldehydes ketones and alcohols?
Alcohols have the highest boiling points as they can form stronger intermolecular hydrogen bonds between alcohol molecules.
Ketones and aldehydes have permanent dipole dipole forces due to the polarity of the C=O bond but cannot form hydrogen bonds and hence have not got as high a boiling point as alcohols.
Alkenes are non polar molecules which only form van der waals intermolecular forces which do not require a lot of energy to break and hence have the lowest boiling point.
What is volatility?
The tendency of a substance to evaporate
Are alcohols volatile?
They have high boiling points and therefore are not as volatile as other substances such as alkenes
What happens when you oxidise a primary alcohol but not under reflux?
Forms an aldehyde
This needs to be distilled off
What happens when you oxidise a primary alcohol under reflux?
Forms a carboxylic acid
What happens when you oxidise a secondary alcohol?
Forms a ketone
What happens when you oxidise a tertiary alcohol?
Tertiary alcohols do not oxidise very easily
What is are the conditions and oxidising agent used when oxidising an alcohol?
Agent - acidified potassium dichromate (K2Cr2O7/H2SO4)
Heat(mild or refluxed)
Colour change from orange to green
What happens when alcohols are combusted?
Alcohols burnt completely if there is enough oxygen to form carbon dioxide and water.
Incomplete combustion leads to carbon monoxide or carbon itself
What happens when alcohols are dehydrated? Give the conditions required
An elimination reaction occurs as water is removed from the parent molecule.
Forms an alkene
Conditions:
Excess concentrated sulphuric acid (or phosphoric acid)
Or
Passing vapours over heated aluminium oxide
What are some uses of ethanol?
Used for….
Drinks
Perfume
Cosmetics
Production of biofuel
