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Esters Revision
• Matching names/structures of esters.
Give examples of:
• saturated and unsaturated hydrocarbons.
• cis–trans (E/Z) isomerism.
• esterification reaction.
HYDROLYSIS OF ESTERSHYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER + WATER CARBOXYLIC ACID + ALCOHOL
The products of hydrolysis depend on the conditions used...
Acidic CH3COOCH3 + H2O CH3COOH + CH3OH
Alkaline CH3COOCH3 + NaOH → CH3COO¯ Na+ + CH3OH
If the hydrolysis takes place under alkaline conditions, the organic product is a water soluble ionic salt
The carboxylic acid can be made by treating the salt with HCl
CH3COO¯ Na+ + HCl → CH3COOH + NaCl
USES OF ESTERSUSES OF ESTERS
Despite being fairly chemically unreactive, esters are useful as ...
• flavourings apple 2-methylbutanoatepear 3-methylbutylethanoatebanana 1-methylbutylethanoatepineapple butylbutanoaterum 2-methylpropylpropanoate
• solvents nail varnish remover - ethyl ethanoate
• plasticisers
© Pearson Education Ltd 2009This document may have been altered from the original
• Describe a triglyceride as a triester of glycerol (propane-1,2,3-triol) and fatty acids.
• Compare the structures of saturated fats, unsaturated fats and fatty acids.
What you should be able to do
NATURALLY OCCURING ESTERS - NATURALLY OCCURING ESTERS - TRIGLYCERIDESTRIGLYCERIDES
• triglycerides are the most common component of edible fats and oils
• they are esters of the alcohol glycerol (propane-1,2,3-triol)
Saponification
• alkaline hydrolysis of triglycerol esters produces soaps• a simple soap is the salt of a fatty acid• as most oils contain a mixture of triglycerols, soaps are not pure• the quality of a soap depends on the oils from which it is made
CH2OH
CHOH
CH2OH
Draw the displayed formula of hexadecanoic acid (palmitic acid)
Draw the skeletal formula of hexadecanoic acid
• Write down the reaction between hexadecanoic acid and propan-1-ol
hexadecanoic acid and propan-1-ol →
propylhexadecanoate + water
C15H31COOH + C3H7OH →
C15H31COOC3H7 + H2O
© Pearson Education Ltd 2009This document may have been altered from the original
Formation of a triglyceride
Skeletal formula of octadec-9-enoic (oleic acid)
Structure of octadeca-9,12-dienoic acid
• Compare the structures of cis and trans isomers of unsaturated fatty acids.
• Compare the link between trans fatty acids, the possible increase in ‘bad’ cholesterol and the resultant increased risk of coronary heart disease and strokes.
• Describe and explain the increased use of esters of fatty acids as biodiesel fuels.
You should be able to:
Cis and trans configurations around a double bond
Skeletal formula of octadec-9-enoic (oleic acid)
Draw the two skeletal formulae of the cis and trans forms of this structure
Structures of cis and trans-octadec-9-enoic acid.
Transesterification for the production of biodiesel
http://www.biodiesel-fuel.co.uk/what-is-biodiesel/
Homework suggestions
• How many C=C bonds are there in a molecule of C17H35COOH?
• How many straight-chain structural isomers are there for this formula?
• Draw and name one pair of cis–trans isomers for this formula.
• Check your fridge. Do your margarines or other fat-containing foods give helpful data about the types of fat they contain?
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