carboxylic acids and esters
- Created by: Lucybarrow444
- Created on: 08-10-19 14:04
what is the structure of carboxylic acid and ester
RCOOH. carboxyllic acid
esters RCOOR
how do you form an ester
Carboxylic acids and alcohols react, in the presence of an acid catalyst, to give esters.
the reaction is reversible and water is always the by-product
carboxylic acid and alcohol will determine the ester made. e.g. butanol + ethanoic acid will make butylethanoate and water.
what happens when reacting with carbonates with ca
will liberate CO2 from carbonates. form salt, water and CO2
how strong are carboxylic acids
weak
what are the physical properties of carboxylic aci
- OH bond in carboxyllic acids form hydrogen bonding and so they have relatively high MP and BP than other similar sized alkanes
- COOH group is very soluble in water due to hydrogen bonding but the hydrocarbon chain of a carboxyllic acid is non-polar and is insoluble. short chain carboxyllic acuds dissolve easily but longer ones is less soluble because the hydrocarbon chain is longer the sollubility of COOH is cancelled out by the insolubility of the hydrocarbon chain
- they have very distinguished melting points and so can be used to distinguish between different carboxylic acids
what are the common uses of esters
solvents
plasticiser (makes plastic more flexible)
perfumes
food flavourings (like pear drops)
what can esters be hydrolysed in and what do they
Esters can be hydrolysed in acid to form carboxyllic acids and alcohol
alkaline conditions to form a salt of carboxyllic acids and alcohol. this will leave the equilibrium to the right as there are less carboxyllic acids to form esters again.
what can vegetable oils and animal fats be hydroly
Vegetable oils and animal fats can be hydrolysed in alkaline conditions to give soap (salts of long-chain carboxylic acids) and glycerol.
what is biodiesel
Biodiesel is a mixture of methyl esters of long-chain carboxylic acids.
how is biodiesel produced
Biodiesel is produced by reacting vegetable oils with methanol in the presence of a catalyst.
why is there an increased use of biofuels
- to conserve crude oil supplies
- to reduce the amount of CO2 released to atmosphere
base hydrolysis
Vegetable oils and animal fats can be hydrolysed in alkaline conditions to give soap (salts of long-chain carboxylic acids) and glycerol.
has to be refluxed
the carboxyllic acid salts dissociate in water
RCOONa --> RCOO- + Na+
how does soap work
Hydrophobic ends of soap molecule all attach to the oil. Hydrophilic ends stick out into the water. This causes a drop of oil to form
These drops of oil are suspended in the water. This is how soap cleans a surface - it causes drops of grease and dirt to be pulled off it and suspended in water. These drops are washed away when you rinse with more water.
how can you identify an ester
Students could identify an ester by measuring its boiling point, followed by hydrolysis to form the carboxylic acid, which is purified by recrystallisation, and determine its melting point.
how could you m are an ester
Students could make esters by reacting alcohols with carboxylic acids, purifying the product using a separating funnel and by distillation.
how are Biodiesel made
fatty acids formed from hydrolysis of triesters are used to create a new ester with methanoic acid
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