Alcohols Flashcards
1
Q
What are the physical properties of alcohols?
A
- Alcohols have polar O-H bond because their electronegativity differs very much.
- This makes alcohol polar molecules.
- Though intermolecular London forces are weak hydrogen bonding between O–H groups makes alcohols boiling points more higher than alkanes.
2
Q
How soluble are alcohols in water?
A
- Due to water only being able to form hydrogen bonds with polar molecules, alcohol is completely soluble in water.
- However the more the chain length increase solubility decreases as influence of -OH group lessens.
3
Q
How are alcohols oxidated?
A
- Primary/ secondary tend to be oxidised by oxidising agent.
- Oxidising mixture is normally potassium dichromate ions and dilute sulfuric acid.
- When oxidised solution turns from orange dichromate ionic solution reduced to green solution with chromium ions.
4
Q
How do prepare aldehydes?
A
- When primary alcohol is gently heated with acidified potassium dichromate, an aldehyde is formed.
- To prevent a carboxylic acid being prepared the aldehyde is distilled.
5
Q
How do you prepare a carboxylic acid?
A
- If primary alcohol is heated strongly with a oxidising agent, a carboxylic acid is formed.
- Heating under reflux ensures any excess aldehyde undergoes oxidation to a carboxylic acid.
6
Q
Do tertiary alcohols undergo oxidation and can you state some reasons why?
A
- Tertiary alcohols do not undergo oxidation.
- When acidified dichromate is added, the solution remains orange.
7
Q
How is an alcohol ‘dehydrated’?
A
- A water molecule being removed from starting material is called ‘dehydration’.
- The alcohol is heated under reflux in presence of acid catalyst - like conc. sulfuric acid/conc. phosphoric acid.
- Product of reaction is an alkene.
8
Q
Can you explain a substitution reaction of an alcohol?
A
- Alcohols can react with hydrogen halides to form a haloalkane.
- When heated under reflex with sulfuric acid and a sodium halide a hydrogen bromide is formed in place.
