Section G Flashcards
What does a primary alcohol oxidise to give?
Aldehyde
What does an aldehyde oxidise to give?
Carboxylic acid
What does a secondary alcohol oxidise to give?
Ketone
Name two oxidising agents that oxidise primary and secondary alcohols
- hot copper (II) oxide
- acidified dichromate
How does the oxidation of primary and secondary alcohols work?
A carbon hydrogen bond is broken and a hydrogen atom it lost
Explain oxidation of tertiary alcohols?
They cannot be oxidised because the carbon that the hydroxyl group is attached to is not bonded to any hydrogen atoms
How does the oxygen to hydrogen ratio change in oxidation and reduction?
Oxidation-increases
Reduction-decreases
What two reagents can be used to oxidise aldehydes and ketones but is not strong enough to oxidise primary and secondary alcohols?
Fehlings and tollens
What is an aldehyde?
A compound where the carbonyl group is on the end of a carbon chain
What is a ketone?
A compound where the carbonyl group is not in the end of a carbon chain
How do you name an aldehyde?
The suffix ‘ane’ is replaced with ‘al’
How do you name a ketone?
Suffix ‘ane’ is replaced with ‘one’
How are aldehydes and ketones related to each other?
They are isomers
How can fehlings and tollens be used?
To distinguish between aldehydes and ketones
How do oxidising agents effect aldehydes and ketones?
Aldehydes oxidise and ketones don’t
How does acidified dichromate effect aldehydes and ketones?
Aldehydes- solution changes from orange to green
Ketones- solution remains orange
How does fehlings test effect aldehydes and ketones?
Aldehydes- solution changes from blue to brick red precipitate
Ketones- solution remains blue
How does tollens test effect aldehydes and ketones?
Aldehydes- silver mirror forms
Ketones- no solver mirror forms
Why can aldehydes be oxidised?
There is a hydrogen bonded to the carbonyl carbon and this carbon-hydrogen bond can be broken and a new bond to the oxygen of the ‘OH’ group can form
Why can’t ketones be oxidised?
They don’t have a hydrogen bonded to the carbonyl carbon which means carbon-carbon bond would have to be broken
What happens when food reacts with the oxygen in the air?
They oxidise and become rancid
What is an antioxidant?
A reducing agent that oxidises easily so prevents other substances in the food from being oxidised
How do you identify the antioxidant in an equation?
Find the reducing agent
