Unit 2 - Nature's chemistry Flashcards
What is meant by the term “free radical”?
A free radical is a highly reactive species containing unpaired electrons.
How can free radicals damage food?
By the removal of an electron.
How does an antioxidant ‘cancel out’ a free radical?
The antioxidant molecule donates an electron to the potentially damaging free radical. A stable electron pair is formed, stabilising the free radical.
Give an example of an antioxidant.
Vitamin C.
How can esters be identified?
Esters can be identified by the name endings ‘yl-oate’. Esters also contain the carboxylate functional group (-COO-).
If the parent alcohol is methanol and the carboxylic acid is hexanoic acid, what is the ester formed?
Methyl hexanoate.
If the parent alcohol is butan-1-ol and the carboxylic acid is propanoic acid, what is the ester formed?
Butyl propanoate.
How are esters made?
By a condensation reaction. Small molecules join together to form a bigger molecule by the elimination of water.
How are esters broken?
By a hydrolysis reaction. Large molecules are broken down into smaller molecules by the addition of water across the ester link.
What are the three steps to a free radical chain reaction?
Initiation, propagation and termination.
How do you identify an ester?
With the ‘COOH’ link.
What is a hydrolysis reaction?
The addition of water to break down a carbon compound.
What is a condensation reaction?
A reaction in which two (or more) molecules join together to produce a single larger molecule, with water or another small molecule formed at the same time.
What can a primary alcohol be oxidised to?
An aldehyde.
If ethanol is oxidised, what is the result?
Ethanal (Primary alcohol is oxidised to become an aldehyde.)
How can an aldehyde be recognised?
With a double bond at the start of a molecule and it having the general formula CnH2nO
What can a secondary alcohol be oxidised to?
A ketone
How can a ketone be recognised?
Ketones contain the carbonyl group in the middle of the carbon chain. CnH2nO is also the general formula as ketones and aldehydes are isomers.
What is a tertiary alcohol oxidised to?
Tertiary alcohols show no reaction when mixed with oxidising agents and tertiary alcohols are not readily oxidised.
What happens when an aldehyde is oxidised?
It becomes a carboxylic acid.
When using acidified potassium dichromate solution as an oxidising agent, what is the colour change observed?
Orange to green.
When using hot copper oxide as an oxidising agent,m what is the colour change that is observed?
Black to red/brown.
When using Tollens reagant as an oxidising agent, what is the colour change observed?
Colourless to silver.
When using Fehlings solution as an oxidising agent, what is the colour change observed?
Blue to brick red.
