Carboxylic acids, esters & fats/oils Flashcards
How can carboxylic acids be identified?
the presence of the carboxyl group (-COOH) and the -oic ending.
What can carboxylic acids react with bases e.g. alkalis to form (neutralisation)?
salts e.g. sodium ethanoate
What can carboxylic acids be reduced to ?
aldehydes and alcohols
What does a reduction reaction involve?
a gain of hydrogen or loss of oxygen which results in a decrease in the oxygen to hydrogen ratio
What are esters made by?
a condensation reaction
What is a condensation reaction?
where 2 small molecules join together to make a larger and water
What is the reaction which produces esters?
esterification
What is the equation for the formation of an ester?
alcohol+ carboxylic acid > ester + water
What do all esters contain?
the ester link
What is the reverse reaction of condensation?
hydrolysis
What are esters (naming)?
alkyl alkanoates
What are the properties of esters?
Esters are immiscible with water (because water is polar whereas esters are non-polar).
Esters are sweet-smelling and volatile (low boiling point)
What are the uses of esters?
flavourings for food
perfumes
solvents for non-polar substances
Describe the experimental set up for making esters?
Hot water bath (used as contents are flammable)
test tube containing alcohol and acid + conc sulphuric acid as a catalyst.
wet paper towel as a condenser (reflux (reflow) cuts down evaporation)
cotton wool
sodium hydrogen carbonate solution (neutralises acids & stops the reaction. Separates ester (oily layer)
What does the equilibrium mixture contain?
carboxylic acid/ alcohol/ ester/ water
What are fats and oils?
esters
What is the alcohol in fats/oils?
glycerol
What is the systematic name for glycerol?
propan-1,2,3-triol
What does glycerol have?
3 hydroxyl groups
Glycerol has 3 hydroxyl groups but what does this mean for fats/oils?
3 ester links
What is the ratio to form one fat/oil?
1 glycerol : 3 fatty acid molecules
What is a fatty acid?
very long hydrocarbon chain with a carboxyl group
What is the reaction called when glycerol + fatty acids > lipids?
condensation
What is the reaction called when fats> glycerol +fatty acids?
hydrolysis
What are fats/oils also called?
triglycerides
lipids
What are all fats and oils (saturated or unsaturated) classified as?
Animal Vegetable Marine (fish oils) high energy foods provide essential fatty acids contain some vitamins (dissolved in the fats/oils)
What are the 2 groups fatty acids are divided into?
saturated fatty acids (e.g stearic acid (C17H35COOH) found in animal fats)
Unsaturated fatty acids (e.g. oleic acid (C17H33COOH) found in vegetable oils)
What do unsaturated have that allows them decolourise bromine water?
C=C
What are the differences between fats and oils?
Fats are solids whereas oils are liquid.
Solid fats have saturated chains whereas liquid oils have unsaturated chains.
Why do saturated fats and unsaturated oils have different melting points?
The saturated, regularly shaped fat molecules pack closely and have lots of London dispersion forces between them > higher m.pt.
Unsaturated oil molecules have irregular shapes (caused by C=C). They pack loosely and have fewer London dispersion forces > lower m.pt.
How can oil become fats?
By hydrogenation/ adding hydrogen
When oils harden and become fats what happens?
they become saturated and m.pt is raised. margarine is an example of this
When oils are hardened what are the fats formed called?
hydrogenated fats
What does too much saturated fats/ animal in our diet cause?
heart disease
