Organics - alcohols

Question 1

Partial oxidation of primary alcohols to form aldehydes

Answer 1

For example, propan-1-ol reacts with POTASSIUM DICHROMATE (VI) IN SULPHURIC ACID to produce propanal and also water

The potassium dichromate (VI) with sulphuric acid is represented as [O]. You have to use a limited amount because this allows for partial oxidation to occur, if you used excess then full oxidation would occur and a carboxylic acid would form instead.

The conditions are to warm it gently and then distil out the aldehyde as it forms.

Question 2

Full oxidation of primary alcohols to produce carboxylic acids

Answer 2

For example, propan-1-ol reacts with POTASSIUM DICHROMATE (VI) IN SULPHURIC ACID to produce propanoic acid and also water.

The potassium dichromate (VI) is presented as [O]. You have to use excess so that full oxidation occurs, if you used a limited amount then partial oxidation would occur and an aldehyde would form instead.

The conditions are to heat it under reflux and to distil off the product when the reaction finishes.

Question 3

Oxidation of secondary alcohols to form ketones

Answer 3

For example, propan-2-ol reacts with POTASSIUM DICHROMATE (VI) IN SULPHURIC ACID to produce propanone and also water

The potassium dichromate (VI) is presented as [O].

Conditions are heating under reflux. Once the ketone is formed it is separated from the reaction mixture by distillation.

Question 4

Oxidation of tertiary alcohols

Answer 4

They cannot be oxidised at all by potassium dichromate (VI), this is because there is no hydrogen bonded to the carbon with the OH group.

Question 5

Reacting alcohols with phosphoric acid to form alkenes

Answer 5

For example, propan-1-ol reacting with phosphoric acid forms propene and also water.

The reagent is the concentrated phosphoric acid which is the dehydrating agent. The conditions are to warm under reflux.

NOTE: Producing alkenes from this method is a possible route to polymers without using monomers derived from crude oil (and thus using up non-renewable crude oil).

This is an elimination reaction (water is eliminated) and also a dehydration reaction (removal of a water molecule)