Alcohols Flashcards
What is a primary alcohol?
An alcohol in which the OH group is attached to a carbon which is attached to just one other carbon atom.
What is a secondary alcohol?
An alcohol in which the OH group is attached to a carbon which is attached to two other carbon atoms.
What is a tertiary alcohol?
An alcohol in which the OH group is attached to a carbon which is attached to three other carbon atoms.
Describe the trend of boiling points in homologous series.
Boiling point increases as molecules get larger as bigger molecules form stronger London forces which take more energy to break.
Why do alcohols have anomalously high boiling points?
They contain hydrogen bonds between the lone pair on oxygen atoms and the delta + charges on hydrogen atoms.
Why are alcohols soluble in water.
They can form hydrogen bonds with water molecules.
Explain the trend of solubility in the alcohols.
As molecules get larger, solubility decreases, as only one hydrogen bond can form per alcohol molecule.
What are the products of complete combustion of alcohols?
Carbon dioxide and water.
Why is ethanol a good fuel?
It contains oxygen, so burns cleanly with little incomplete combustion.
It can be produced naturally via fermentation so is renewable.
It is a liquid so easy to store.
Give the conditions for the dehydration of alcohols
Heat under reflux
Concentrated sulphuric/ phosphoric acid catalyst
What does elimination mean?
The removal of atoms or groups from neighbouring carbon atoms to form an alkene and release a small molecule (eg water)
Which is the easiest type of alcohol to eliminate water from?
Tertiary
Describe the dehydration of alcohols.
An alcohol is heated with a concentrated acid catalyst to give a C=C double bond and a water molecule
What are the two chemicals required to oxidise and organic compound?
Potassium dichromate (K2Cr2O7) Dilute sulphuric acid
What can be observed when an organic molecule is oxidised?
Solution changes from orange to green (or blue).
What are the potential products of oxidation of primary alcohols?
Aldehydes or carboxylic acids.
How is the oxidising agent shown in an oxidation reaction?
[O]
Give a general equation for the formation of an aldehyde from a primary alcohol.
primary alcohol + [O] —–> aldehyde + water
What are the conditions for oxidising a primary alcohol to an aldehyde?
Heat and distillation.
Give a general equation for the formation of a carboxylic acid from a primary alcohol.
primary alcohol + 2[O] ——-> carboxylic acid + water
Give a general equation for the formation of a carboxylic acid from an aldehyde.
aldehyde + [O] ——-> carboxylic acid
What is the product of the oxidation of a secondary alcohol?
A ketone
Give a general equation for the formation of a ketone from a secondary alcohol.
secondary alcohol + [O] ——> ketone + water
What are the conditions for oxidising a primary alcohol to a carboxylic acid?
Heat under reflux
