Reactions Of Alcohols Flashcards
How does the amount of energy released per mole during combustion of alcohols change with chainlength?
As the number of carbon atoms in the chain increases, the amount of energy released per mole also increases.
Describe the colour change which shows that an alcohol has been oxidised.
- Orange to green
- The dichromate (VI) ions are reduced to chromium (III) ions
What is the oxidising agent used to oxidise alcohols?
- Potassium Dichromate acidified with Sulphuric Acid
What two products can primary alcohols be oxidised to?
- Aldehydes
- Carboxylic Acids
Describe the method to preparing an aldehyde from a primary alcohol.
Use distillation to remove the aldehyde from the reaction mixture as it forms.
How would you represent the oxidising agent used in a balanced equation?
[O] —> Alcohol to Aldehyde
2[O] —> Alcohol to Carboxylic Acid
How is a Carboxylic acid prepared from a primary alcohol?
Alcohol is heated strongly under reflux conditions with an excess of acidified potassium dichromate to form Carboxylic acid and water
What is reflux?
The continuous boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling dry.
What is formed when secondary alcohols are oxidised using acidified dichromate?
Ketones and water
What is the result of oxidising a tertiary alcohol with acidified dichromate?
No reaction takes place
—> solution remains orange
Describe how you would set up apparatus to carry out distillation.
- Fill a clamped round bottom flask with anti-bumping granules and the reaction mixture to prevent large bubbles and place flask above a heat source
- Connect the top of the condenser to the distillation flask and connect rubber tubing to both ends of the condenser for water flow
- Place a cap on top of the distillation flask to prevent vapour escaping and insert a thermometer into the flask to determine temperature
- Place a conical flask at the end of the condenser to collect the condensed vapour
Describe how you would set up apparatus to carry out a reflux reaction.
- Fill the reflux flask with anti-bumping granules and the reaction mixture and attach to a stand using a clamp and place above a heat source.
- Attach the condenser to the reflux flask and connect rubber tubing for water flow
Describe the reaction which results in the dehydration of an alcohol.
- An OH group is lost from one carbon
- An H atom is lost from an adjacent carbon
- Double bond forms between these 2 carbons
What happens when alcohols react with hydrogen halides?
- Heated under reflux with sulphuric acid and a sodium halide
- Produces a haloalkane in a two step reaction using a hydrogen halide intermediate
How are esters formed?
Reacting a Carboxylic acid with an alcohol in the presence of a strong acid catalyst
What is the general name of an ester based off?
Alkyl Carboxylate
e.g. propanol + ethanoic acid —> Propyl Ethanoate
