2g) - Oxidation of Food Flashcards
What is oxidation for carbon compounds
Oxidation is an increase in the oxygen to hydrogen ratio
What is reduction for carbon compounds
Reduction is a decrease in the oxygen to hydrogen ratio
What are aldehydes and ketones
Aldehydes and ketones are molecules containing a carbonyl functional group C=O
What can primary alcohols oxidise to
Primary alcohol ——> aldehyde ——> carboxylic acid
What can secondary alcohols oxidise to
Secondary alcohol ——> ketone
What can a tertiary alcohol oxidise to
Tertiary alcohol ——> does not oxidise
How to name an aldehyde?
Step 1: Name the longest chain that contains the carbonyl group
Step 2: Number chain with carbonyl
= 1
Step 3: Name the branches and number according to step 2
Step 4: If multiple of the same branch use di-, tri- etc, if different types of branch then name alphabetically
How to name a ketone
Step 1: Name the longest chain that contains the carbonyl group
Step 2: Number chain with from end closes to carbonyl
Step 3: Name the branches and number according to step 2
Step 4: If multiple of the same branch use di-, tri- etc, if different types of branch then name alphabetically
What can hot copper oxide or acidified dichromate solutions be used to oxidise
- primary alcohols into aldehyde and then to carboxylic acid
- secondary alcohols to ketone
What can oxidising agents be used for
Oxidising agents can be used to differentiate between an aldehyde and a ketone
What happens to an aldehyde with fehlings solution
With aldehyde - blue ——> brick red
What happens to an aldehyde with Tollens reagent
With aldehyde - colourless ——> silver mirror
What happens to an aldehyde with acidified dichromate
With aldehyde - orange ——> green
What are many flavour and aroma molecules
- Many flavour and aroma molecules are aldehydes
What does oxygen from the air cause
Oxygen from the air causes oxidation of food
What type of flavour does the oxidation of edible oils give to food
The oxidation of edible oils gives food a rancid flavour
Hot copper (II) oxide changes from black to which colour?
Brown
What are the three chemicals involved in differentiating between aldehydes and ketones
- fehlings solution
- tollens reagent
- acidified dichromate
Do ketones produce any colour change with specific chemicals
No ketones do not change colour when using oxidising agents
Why can tertiary alcohols not be oxidised
they don’t have a hydrogen atom attached to the same carbon atom as the hydroxyl group
What are antioxidants
- molecules that prevent unwanted oxidation reactions occurring
- substances that are easily oxidised and oxidise in place of the compounds they have been added to protect
- can be identified as the substance being oxidised in a redox equation
