Oxidation of Food Flashcards
Name six chemicals found in food.
Aldehydes Ketones Alcohols Carboxylic acids Fats Oils
What can happen to chemicals in food?
They can be oxidised by oxygen in the air, which spoils the food.
Between the alcohol and alkane with the same number of carbons, which has the higher boiling point?
Alcohol
What happens to the boiling points of alcohol as the number of carbons increase?
It increases.
Explain the difference in the bonding of alcohols compared to alkanes.
Alcohol molecules have a polar -O-H group, resulting in hydrogen bonding. The hydrogen bonds are much stronger compared to the London dispersion forces between alkane molecules. This means alcohols require more energy to separate, giving higher boiling points than alkanes.
How can alcohols be classed?
Primary, secondary and tertiary.
How many carbons are attached to the carboxyl group in a primary, secondary, and tertiary alcohol?
1, 2, 3.
What is a diol?
An alcohol with two hydroxyl groups.
What is an alcohol with three hydroxyl groups called?
Triol
Name a common triol.
Glycerol (propane-1,2,3-triol) - the alcohol part of fats and oils.
Why do diols and triols have high boiling points?
Due to strong hydrogen bonding between molecules.
What does it mean if a product has a higher oxygen : hydrogen ratio than the reactant?
Oxidation has taken place.
Can tertiary alcohols be oxidised?
No
What are primary alcohols oxidised to?
Aldehydes, and then oxidised again into carboxylic acids.
What can secondary alcohols be oxidised to?
Ketones
What can a carboxylic acid be reduced to?
The corresponding aldehyde and alcohol. The oxygen:hydrogen ratio decreases from acid to alcohol, indicating a reduction.
What do carboxylic acids neutralise?
Bases, to form salts.
What can salts of a carboxylic group be used as?
Preservatives in food and prevent the growth of mould.
What is particularly susceptible to oxidation?
Oils
What happens when food spoils, due to oxidisation?
Products are formed, some of which have an unpleasant smell and taste. These products can be oxidised further, at the double bonds, releasing volatile aldehydes which also smell.
How is an oil of fat described when oxidised/spoiled?
Rancid
What is used to reduce the oxidation of chemicals in food?
Antioxidants - they extend the shelf life of food.
What does an antioxidant do?
Some react with the oxygen, while others prevent the formation of soapy tasting peroxides.
Name a common antioxidant used in food.
Ascorbic acid (vitamin C)
What is an isomer?
Molecules that have the same molecular formula but a different arrangement of atoms.
What is chain isomerism?
The atoms are arranged in a completely different order resulting in branches.
What is position isomerism?
The basic carbon skeleton remains unchanged but functional groups can be moved around.
What similar chemical compounds exhibit isomerism?
Esters, aldehydes, ketones, alcohols, and carboxylic acids.
Which molecules can’t have positional isomers, and why?
Aldehydes and carboxylic acids, because the functional group must always be on the end carbon.
What is functional group isomerism?
Molecules that contain different functional groups.
