Reactions of alcohols Flashcards
What is the usual oxidising mixture used for the oxidation of alcohols?
A solution of potassium dichromate(VI) acidified with dilute sulfuric acid
The mixture is commonly represented as K2Cr2O7 in reaction equations.
What color change indicates the reduction of dichromate(VI) ions during oxidation?
From orange to green
The green solution contains chromium(III) ions.
What are the products formed when alcohols burn completely in oxygen?
Carbon dioxide and water
The combustion of ethanol is represented as: C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l).
What type of reaction occurs when primary alcohols are oxidised?
They can be oxidised to either aldehydes or carboxylic acids
The specific product depends on the reaction conditions.
What is the technique used to prevent the further oxidation of aldehydes to carboxylic acids?
Distillation
This technique allows the aldehyde to be removed from the reaction mixture as it forms.
What is produced when a primary alcohol is heated strongly under reflux with an excess of acidified potassium dichromate(VI)?
A carboxylic acid
Heating under reflux ensures complete oxidation of the alcohol.
What happens to secondary alcohols during oxidation?
They are oxidised to ketones
Ketones cannot be further oxidised using acidified dichromate(VI) ions.
True or False: Tertiary alcohols undergo oxidation reactions.
False
Tertiary alcohols do not change color when treated with acidified dichromate(VI).
What is dehydration in the context of alcohols?
The removal of a water molecule from the starting material
Dehydration of alcohols results in the formation of alkenes.
What type of reaction is the dehydration of an alcohol classified as?
An elimination reaction
This reaction typically involves heating the alcohol with an acid catalyst.
What do alcohols react with to form haloalkanes?
Hydrogen halides
The reaction requires heating under reflux with sulfuric acid and a sodium halide.
What is the overall equation for the reaction of propan-2-ol with NaBr and H2SO4?
C3H8O + NaBr + H2SO4 → C3H7Br + NaHSO4 + H2O
This shows the substitution of the alcohol group -OH in propan-2-ol.
