Carboxylic Acids and Derivatives Flashcards
what is a carboxylic acid functional group
-COOH (C=O and C-OH)
how do you name carboxylic acids
-oic acid
are carboxylic acids soluble in water? why? what influences?
yes
acid group can form hydrogen bonds with water molecules
what are intermolecular forces in carboxylic acids
hydrogen bonds in solid states - very strong
what are esters
formed from carboxylic acids and alcohols
ester general formula
RCOOR’ (C=O, C-O-C)
how do you name esters
start with group that replaced the hydrogen, then the acid
e.g. propyl (from alcohol) ethanoate (from carboxylic acid)
what characteristic physical properties do esters have
volatile, pleasant fruity smells e.g. apple, pear drops
what are some uses of esters
long chain: flavourings and perfumes
short chain: solvents
also plasticisers
what are some common natural esters
fats and oils
equation for equilibrium by ethanoic acid
CH3COOH <—> CH3COO- + H+
what happens to the negative charge on the ethanoate ion in terms of electrons
electrons delocalise so the negative charge is shared across the whole of the carboxylate group
how could you distinguish carboxylic acids from other -OH containing compounds
add NaHCO3, acids will produce sodium salt, water and carbon dioxide
write an equation for the reaction of ethanoic acid with NaOH
CH3COOH + NaOH –> H2O + CH3COO-Na+
write an equation for the reaction of ethanoic acid with Na2CO3
2CH3COOH + Na2CO3 –> 2CH3COO-Na+ + H2O + CO2
what catalyst is needed for the formation of esters from alcohols and carboxylic acids
concentrated strong acid e.g. H2SO4
what catalyst is needed for the hydrolysis of esters
dilute strong acid e.g. H2SO4
what is an alternative method of hydrolysis
base hydrolysis
what are the advantages of base hydrolysis
reaction goes to completion due to neutralisation by base - more product in the mixture than acid catalysed hydrolysis
which alcohol forms esters that make up animal and vegetable oils
glycerol / propane-1,2,3-triol
what is the difference between oil and fat
oils are liquid at room temperature, fats are solid
fats are usually saturated, oils are not
what are the products of hydrolysing fats and oils
propane-1,2,3-triol and sodium salts of the acids that make up the ester (hydrolysed with NaOH)
what are the uses of propane-1,2,3-triol and sodium salts
soaps and cleaning products
what does the long hydrocarbon chain of carboxylate ion do
mixes with grease
what does the COO- group do
mixes with water
how does the carboxylate ion with a long carbon chain make a good cleaning agent
means that grease can be removed from water
what is the systematic name of glycerol
propane-1,2,3-triol
what are some common used of glycerol
- used in the pharmaceutical and cosmetic preparation
- solvent in many medicine
- solvent in food industry
- plasticising various materials like sheets and gaskets, cellophane and paper
how do you make biodiesel
NaOH catalyst, 60 degrees celsius
lipids (fats/oils - esters) + 3CH3OH –> 3methylesters + glycerol
what does transesterification mean
converting one type of ester to another
what kind of crops is biodiesel made from
rapeseed oil or soybean oil
how is the reaction mixture of biodiesel purified and separated
selling tank or centrifuge, remove remainder with water
add acid to neutralise excess alkali catalyst
solid soap is formed - easy to remove
how is the reaction mixture of biodiesel purified and separated
selling tank or centrifuge, remove remainder with water
add acid to neutralise excess alkali catalyst
solid soap is formed - easy to remove
what is the problem with producing biodiesel
crops that could be used to make food are being used to make fuel - are resources being best used
what are carboxylic acid derivatives
molecules that have the acyl group as part of their structure, formed from carboxylic acids
name 2 acid derivatives and give their functional groups
acyl chlorides: ROCOCl
acid anhydrides: RCOOCR / (RCO)2O
which factors determine how readily the acylation of a nucleophile by an acid derivative occurs
- magnitude of the delta + charge on the carbonyl carbon, which depends on the electronegativity of the atom/group being substituted
- how easily the atom/group being substituted is lost
- how good the nucleophile is (how readily will it donate electrons)
what effect do the Cl and O atoms in acyl chlorides/acid anhydrides have on the partial charge of the carbonyl carbon
increase the partial + charge by attracting electrons
this means that they react more readily with nucleophiles
are acyl chlorides or acid anhydrides more reactive
acyl chlorides
what is the name of the mechanism by which acyl chlorides and acid anhydrides acylate nucleophiles
addition-elimination
if the nucleophile is ammonia for acylation of acyl chlorides or acid anhydrides, what is the product of reaction
an amide
if the nucleophile is a primary amine, what are the products of the acylation of acyl chlorides or acid anhydrides
N-substituted amide
if the nucleophile is an alcohol, what are the products of acylation of acyl chlorides or acid anhydrides
an ester
if the nucleophile is water, what are the products of the acylation of acyl chlorides or acid anhydrides
carboxylic acid (hydrolyses ester linkage)
what is the name of the acylation of acyl chlorides/acid anhydrides with water as a nucleophile
hydrolysis
what is a commercially important acylation reaction
manufacture of aspirin
what are the advantages of using ethanoic anhydride as an acylating agent over ethanoyl chloride
it is cheaper, less corrosive and does nor react as readily with water
it is safer, as ethanoic acid is produced, rather than HCl which is corrosive
what would you observe in a melting point determination if the sample was not pure
sample melts over a range
sample’s melting point is below accepted value due to impurities disrupting structure
why might the melting point appear different to the true value
temperature of material in the machine might be different to the temperature shown on the thermometer - apparatus error
when removing flue gases, what are the issues
disposal of large amounts of CaSO3 and CO2 is produced
what condition are needed to form methyl esters from an acid anhydride or acyl chloride
react w methanol and heat gently under reflux
when purifying by recrystallisation, why is the minimum volume of hot solvent used
so that a saturated solution is created, so that as many crystals will fall out of solution as possible when it is cooled
why is the solution filtered hot when purifying by recrystallisation
to remove insoluble impurities and ensure that the crystals do not form in the filter paper
why is the solution cooled in an ice bath when purifying by recrystallisation
remove soluble impurities
how would you separate the crystals from the reaction mixture when purifying by recrystallisation
filter under reduced pressure using a Buchner funnel
why might percentage yield be below 100% for recrystallisation
- product is lost during filtration, drying and weighing - spills, not all transferred from one apparatus to another
- product is left dissolved in solution - some does not crystallise, sample still wet
