carboxylic acids and derivatives Flashcards
(39 cards)
carboxylic acids solubility in water and trend
The smaller carboxylic (up to C4) acids dissolve in water in all proportions but after this the solubility rapidly reduces. They dissolve because they can hydrogen bond to the water molecules.
acidity of carboxylic acids
The carboxylic acid are only weak acids
in water and only slightly dissociate, but
they are strong enough to displace
carbon dioxide from carbonates.
trend in strength of carboxylic acids
Increasing chain length pushes
electron density on to the COOion, making it more negative and
less stable. This make the acid
less strong.
what atom makes a carboxylic acid stronger and why
chlorine - Electronegative chlorine atoms withdraw electron density from the COOion, making it less negative and more stable. This make the acid more strong.
Salt formation reactions of carboxylic acids
acid + metal (Na) = salt + hydrogen
2CH3COOH + 2Na = 2CH3COO- Na+ + H2
acid + alkali (NaOH) = salt + water
CH3COOH + NaOH = CH3COO- Na+ + H2O
acid + carbonate (Na2CO3) = salt + water + CO2
2CH3COOH + Na2CO3 = 2CH3COO- Na+ + H2O + CO2
how to test for carboxylic acids
The effervescence caused by the production of CO2
with carboxylic acids with solid Na2CO3 or
aqueous NaHCO3 can be used as a functional
group test for carboxylic acids
which carboxylic acid is an exception and CAN be oxidised
methanoic acid - Carboxylic acids cannot be oxidised by using
oxidising agents but methanoic acid is an
exception as its structure has effectively an
aldehyde group
esterification reaction and conditions
carboxylic acid + alcohol = ester + water
heating under reflux and H2SO4 catalyst
what type of reaction is esterification
reversible
naming esters
The bit ending in –yl comes from
the alcohol that has formed it
and is next to the single bonded
oxygen.
The bit ending in –anoate
comes from the carboxylic
acid and includes the C in
the C=O bond
esterification reaction equation for ethanoic acid and ethanol
CH3COOH + CH3CH2OH =(reversible)= CH3COOCH2CH3 + H2O
uses of esters
perfumes, flavourings
how to reverse esterification reagents conditions and reaction name
hydrolysis,
dilute HCl, heat under reflux
other reaction to reverse esterification reagents conditions etc
hydrolysis with dilute sodium hydroxide
heat under reflux
problem with acid hydrolysis of esters
reversible so doesnt give a good yield
why is hydrolysis with NaOH not reversible
carboxylic acid salt produced is an anion, resistant to attack from nucleophiles such as alcohols so not reversible
what is formed when you hydrolise fats and vegetable oils
propane-123-triol (glycerol)
long chain carboxylic (fatty) acids
uses of glycerol and why
used in cosmetics, food and glues as it can hydrogen bond so is soluble in water
use of long chain fatty acids and why
soap
polar COO- end is hydrophilic and mixes with water
non-polar hydrocarbon end is hydrophobic and mixes with grease
this enables grease and water to mix
how to make biodiesel reagent and conditions
react vegetable oil/fat with methanol in the presence of a strong alkali catalyst
are acyl chlorides more reactive than carbox acids and why
yes, because Cl and -OCOCH3 are good leaving groups
reaction of acyl chloride with water info
forms carboxylic acid and produces steamy white HCl fumes (mostly gives HCl fumes not carbox acid)
room temp, water
general equation for acyl chloride + water
RCOCl + H2O = RCOOH + HCl
what mechanism do acyl chlorides and acid anhydrides do
nucleophilic addition-elimination
