2d) - Esters Fats And Oils Flashcards
What is an ester
An ester is a molecule containing an ester link - COO -
What happens in a condensation reaction
In a condensation reaction, two molecules are joined together with the elimination of a small molecule
Which reaction are esters formed by?
Esters are formed by a condensation reaction between an alcohol and a carboxylic acid with concentrated sulphuric acid as a catalyst
Which catalyst is used in the esters experiment
Concentrated sulphuric acid
What is the equation for an ester
Alcohol + carboxylic acid ——> ester + water
How to name an ester
- first part comes from the parent alcohol
- second part comes from the parent carboxylic acid
What is the small molecule eliminated when an ester link is formed
When an ester is link is formed by the reaction between a hydroxyl group and a carboxyl group, the small molecule eliminated is water
What happens in a hydrolysis reaction
In a hydrolysis reaction, a molecule reacts with water to break down into smaller molecules
What is produced when esters are hydrolysed
Esters can be hydrolysed to produce an alcohol and a carboxylic acid
What is the equation for breaking down (hydrolysis) of an ester
Ester + water ——> acid + alcohol
<——
What can esters be used for
Esters are used as flavourings and fragrances as many have pleasant fruity smells. Esters are also used as solvents for non-polar compounds that do not dissolve in water
What is the equipment required for the making esters experiment
- beaker x2
- test tube
- paper towel
- elastic band
- concentrated sulphuric acid
- sodium hydrogen carbonate
How do we know an ester has formed
Ester makes oily/solid layer
Why is a wet paper towel with elastic band used
Acts as a condenser
Why can we not use a Bunsen burner in the esters experiment
Alcohol is flammable so we don’t use a Bunsen burner
Which temperature can water boil to
Water only boils to 100 degrees celcius
What is the role of fats and oils
Fats and oils are an essential part of the diet. They provide the body with energy
What type of source of energy are fats and oils
Fats and oils are a more concentrated source of energy than carbohydrates
How are edible fats and oils formed
Edible fats and edible oils are esters formed from the condensation of glycerol and three carboxylic acid molecules
What is glycerol
Glycerol is a trihydric alcohol it has three alcohol groups the correct name is propan 1,2,3 triol
What are the carboxylic acids in fats and oils known as
The carboxylic acids are known as ‘fatty acids’ and can be saturated or unsaturated straight - chain carboxylic acids, usually with long chains of carbon atoms
Draw the structure of glycerol
Check jotter for answer
Draw the structure of the fatty acids
Check jotter.
What is the mole ratio of fatty acids to glycerol in fats and oils
Fats and oils are formed by the combination of 3 moles of fatty acids to 1 mole of glycerol - a triglyceride
How many ester linkages are in one fat/oil
There are 3 ester linkages in the one molecule
Which of edible fats and oils have a lower melting point
Edible oils have a lower melting point than edible fats
Draw an equation showing the condensation of glycerol and three fatty acids also showing what is produced
Check jotter for answer
What do double binds in fatty acid chains prevent
Double bonds in fatty acid chains prevent oil molecules from packing closely together.
What does a greater number of double bonds present mean
The greater the number of double bonds present, the weaker the Van der waals (LDF) forces
What is the trend between the degree of unsaturation and melting point
The greater the degree of unsaturation , the lower the melting point
How many LDFs do fats have
Fats have higher melting points so more LDF
How many LDFs do oils have
Oil - lower melting point so less LDFs
What is the relationship between double bonds and melting points
Double bonds in fatty acids chains prevent oil molecules form packing closely together, so the greater the number of double bonds present the weaker the Van der waals (LDF) forces of attraction. The greater the degree of unsaturation the lower the melting point
What do unsaturated compounds decolourise quickly
Unsaturated compounds quickly decolourise bromine solution
What do the bromine molecules do to the double bonds in an addition reaction
The bromine molecules add across the carbon - carbon double bonds in an addition reaction
What does the greater the number of double bonds present in a substance indicate
The greater the number of double bonds present in a substance, the more bromine solution can be decolourised
Fats and oils are :
- a concentrated source of energy
- essential for the transport and storage of fat -soluble vitamins in the body
What state are fats at room temp
Fats are solids at room temperature
Why are fats solid at room temperature
Because they have a linear arrangement and can pack closely together it means their London dispersion forces are stronger between the molecules. Because they cab get closer together their interactions are stronger which gives them a higher melting point
What state are oils at room temperature
Liquid
Why are oils liquid at room temperature
Due to the double bonds in oils it is much more difficult to get the molecules to pack closely together which means the London dispersion forces between the molecules are weaker because they can’t interact as strongly which means the melting point will be lower
How can you increase the melting point of an oil
We can increase the melting point of an oil by hardening the oil. This is done by hydrogenation where you add hyrdrogen to the double bond breaking apart the double bond making it more saturated which in turn increases the melting point
Can an alkali being added in a reaction produce an ester
No alkalis break up esters
