carboxylic acids and derivatives Flashcards
what is a carboxylic acid
COOH
how do you name carboxylic acids
-oic acid
are they soluble in water
yes, acid group can form hydrogen bonds with water molecules
what intermolecular forces in carboxylic acids
hydrogen bonds in solid state
what are esters
formed from carboxylic acids and alcohols
RCOOR’
naming esters
start with the group that has replaced the hydrogen the acid part
what physical properties do esters have
volatile, pleasant fruit smells
uses of esters
flavourings,
perfumes
solvents
plasticisers
common natural esters
fats
oils
how could you distinguish carboxylic acids from other OH containing compounds
NaHCO3
acids will produce sodium salt water and carbon dioxide
what catalyst is needed for the formation of esters from alcohols and carboxylic acids
concentrated strong acids
H2SO4
what catalyst is needed for the hydrolysis of esters
dilute strong acid
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 catalyst hydrolysis
what is the difference between oil and fat
oils are liquid at room temp
fats are solid that are usually saturated
how do you make biodiesel
NaOH catalyst
lipids + 3CH3Oh -> 3 methyl esters + glycerol
what does transesterification mean
converting one type of ester to another
how is the reaction mixture of biodiesel purified and separated
settling tank or centrifuge- remove remainder with water
add acid to neutralise excess alkali catalyst
solid soap is formed
what is the problem with producing biodiesel
crops that could be used to make food are being used to make fuel
what are carboxylic acid derivatives
molecules that have the acyl group as part of their structure
formed from carboxylic acids
name two acid derivatives and give their functional groups
acyl chlorides RCOCL
acid anhydrides RCOOCR
which factors determine how readily the acylation of a nucleophile by an acid derivative occurs
magnitude of the delta + charge on the carbonyl carbon
how easily the atom being substituted is lost
how good the nucleophile is
what effect does the Cl and O in AC\AA have on the partial charge of the carbonyl carbon
increases the partial + charge by attracting electrons, this means that they react more readily with nucleophiles
are more AC or AA more reactive
AC
what is the name of the mechanism by which Ac and AA nucleophiles
addition-elimination
if the nucleophile is ammonia for the acylation of AC or AA what are the products
an amide
if the nucleophile is a primary amine, what are the products of the acylation of AC or AA
N-substituted amide
if the nucleophile is an alcohol, what are the products of the acylation of Ac or AA
ester
if the nucleophile is water, what are the products of the acylation of AC or AA
carboxylic acid
what is a commercially important acylation reaction
manufacture of asprin
what are the advantages of using ethanoic anhydride as an acylating agent over ethanoyl chloride
cheaper, less corrosive, does not react readily with water, safer
what would you observe in a melting point determination if the sample was not pure
sample melts over a large range
sample’s melting point is below the accepted value
why might the melting point appear different to the true value
temperature of the material in the machine might be different to the temperature shown on the thermometer
when removing flue gases what are the issues
disposal of large amounts of CaSO3 and CO2 is produced
what conditions are needed to form methyl esters from an AA or AC
methanol
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 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
to ensure that as many crystals as possible fall out of solution
how would you separate the crystals from the reaction mixture when purifying by recrystallisation
filter under reduced pressure using a Buchner funnel
