| what is the functional group of an ester | ester link
-COO- |
| how is an ester formed | when a carboxylic acid molecule reacts with an alcohol molecule in a condensation (esterification) reaction |
| what is the catalyst for an esterification reaction | concentrated sulphuric acid |
| what ester is formed when you react ethanol and propanoic acid | ethyl propanoate |
| what ester is formed when you react butanoic acid and ethanol | ethyl butanoate |
| what are the uses of esters | artificial flavourings
perfumes
solvents for non polar solutes |
| what is a condensation reaction | when two molecules are joined with the elimination of a small molecule - water |
| what do you get when you react an alcohol and a carboxylic acid | an ester and water |
| what is the functional group of an ester | ester linkage
-COO- |
| how is the rate of an esterification reaction increased | by heating the reaction mixture and using concentrated sulphuric acid as a catalyst. |
| are esterification reactions reversible | yes |
| how do you draw an ester | the H from the alcohol and the OH from the carboxylic acid form water
replace these with the ester linkage |
| how do you make esters in a lab | equal quantities of the reactants (alcohol and carboxylic acid) are added to a test tube
concentrated sulphuric acid is added as a catalyst
a wet paper towel is put around the top of the test tube to act as a condenser
the tube is placed into a beaker of hot water/water bath
reaction mixture is poured onto sodium hydrogen carbonate solution to neutralise the concentrated sulphuric acid and any unreacted carboxylic acid |
| what is evidence that an ester has formed when making them in a lab | there is a distinct smell
two layers are formed |
| why are bunsen burners not used when making esters in the lab | alcohols are flammable |
| are esters polar or non polar | non polar |
| what is hydrolysis | large molecules are broken down into smaller molecules by reaction with water
it is the opposite to condensation |
| what do you get upon reacting propyl methanoate with water | propanol
methanoic acid |
| what bond on the ester is broken during hydrolysis | ... |
| what types of hydrolysis are reversible | acid catalysed hydrolysis is reversible
alkali catalysed hydrolysis is not |
| how do you carry out the hydrolysis of esters in a lab | they are heated under reflux: heating the mixture with a condenser attached
this ensures that volatile compounds do not escape and allows the reaction to take place at a higher temperature |
| what is the role of fats and oils in our diets | the provide us with energy
they are essential for the transport of fat soluble vitamins |
| what is the difference between fats and oils | fats are solids and oils are liquids |
| are fats and oils soluble in water | no |
| describe the volatility of fats and oils | they are very volatile as they are esters |
| how are edible fats and oils formed | as they are esters they are formed from the condensation reaction of glycerol with three fatty acid molecules (carboxylic acids)
each molecule of the alcohol condenses with 3 molecules of fatty acid
(R1, R2,k R3 are long carbon chains which can be the same or different) |
| what is another name for glycerol | propane-1,2,3-triol |
| how many OH groups does glycerol have | three
therefore it can form three ester links with fatty acid molecules to form a triglyceride |
| what are fatty acid molecules | saturated or unsaturated straight chain carboxylic acids with usually long chains of carbon atoms. They contain an even number of carbon atoms |
| what kind of fatty acids do fats tend to be formed from | saturated fatty acids |
| what kind of fatty acids do oils tend to be formed from | unsaturated fatty acids |
| is there a higher degree of unsaturation in oils or fats | in oils |
| describe the structure of fats | fats are saturated which means more efficient packing and therefore stronger van der waals interactions
because of this fats have a higher melting point than oils and more energy is required to separate the molecules, so they are solids |
| describe the structure of oils | oils are unsaturated meaning they will have a distorted structure that can't pack as closely and weaker van der waals interactions..
lower melting point than fats, less energy required to separate molecules, so are liquids. |
| what happens during an addition reaction of bromine reacting with unsaturated compounds | bromine molecules add across the carbon-carbon double bond
the greater the number of double bonds of a substance, the more bromine solution can be decolourised |
| what happens when an oil is shaken with bromine water | the brown colour of bromine water is decolourised
this indicates the presence of double bonds in the oil molecules |
| what happens when a fat is dissolved in an organic solvent and then shaken with bromine water | no decolourisation occurs with some fats and onlhy slight or slow decolourisation with others
this indicates that fats may contain no double bonds or fewer double bonds than oils |
| what is meant by monounsaturated | only one carbon to carbon double bond |
| what is meant by polyunsaturated | more than one carbon to carbon double bond |
