Oxidation and the chemistry of cooking Flashcards
What are alcohols?
Carbon compounds that contain the hydroxyl functional group (-OH)
Rules of naming alcohols?
- numbering from the side which gives the -OH the lowest number
- ensuring the -OH takes priority over any branches
What is a primary alcohol?
When the carbon bonded to the hydroxyl group is bonded to a maximum of 1 other carbon
What is a secondary alcohol?
When the carbon bonded to the hydroxyl group is bonded to 2 other carbons
What is a tertiary alcohol?
When the carbon bonded to the hydroxyl group is bonded to 3 other carbons
What does the boiling point of alcohols increase as they have more -OH groups?
Adding hydroxyl groups means the molecules are being held together by hydrogen bonding meaning much more energy has to be supplied to overcome the hydrogen bonding
Name 2 suitable oxidising agents:
• Acidified potassium dichromate
• Hot copper (||) oxide
When tertiary alcohols are oxidised what happens?
Tertiary alcohols do no undergo oxidation readily
When primary alcohols are oxidised what happens?
They produce aldehydes
When secondary alcohols are oxidised what happens?
They produce ketones
How can aldehydes and keystones be identified?
By the presence of the carbon - oxygen double bond (carbonyl group)
Where is the carbonyl group in an aldehyde?
At the end of the carbon chain and has a hydrogen atom attached to it
Where is the carbonyl group in a ketone?
Joined to 2 other carbon atoms and does not have a hydrogen attached to it
What takes priority when naming branches aldehydes and ketones?
The carbonyl functional group
When naming a ketone what is it necessary to specify?
The number of the carbonyl group
E.g. the 3 in 4-methyloctan-3-one
What are the 3 most common oxidising agents used to oxidise aldehydes?
Fellings solution, Tollens reagent and acidified potassium dichromate
Can ketones oxidise?
No
Can aldehydes oxidise?
Yes
Colour change observed when using acidified potassium dichromate solution?
Orange to green
Colour change observed when using Fehlings solution?
Blue to orange/red
Colour change observed when using tollens reagent?
Colourless to silver
Oxidation of primary alcohols:
Primary alcohols -> Aldehydes -> carboxylic acids
Oxidation of secondary alcohols:
Secondary alcohol -> ketone
Oxidation of tertiary alcohols:
Not readily oxidised
Oxidation occurs when… (in relation to oxygen)
There is an increase in the oxygen to hydrogen ratio
Reduction occurs when… (in relation to oxygen)
There is a decrease in the oxygen to hydrogen ratio
When naming carboxylic acids ____________ takes priority
The carboxyl group
