carboxylic acids and derivatives Flashcards
functional group and naming of carboxylic acids
COOH functional group ending, end in -oic acid, e.g. ethanoic acid
acidity of carboxylic acids
carboxylic acids are weak acids and only partially dissociate in water.
solubility of carboxylic acids in water
as the acid gets larger, solubility decreases. the acids can only dissolve as they can form hydrogen bonds with the water
salt reactions of a carboxylic acid
acid + metal -> salt + hydrogen
acid + alkali -> salt + water
acid + carbonate -> salt + water + carbon dioxide
test for carboxylic acids
add sodium carbonate
effervescence caused due to production of carbon dioxide
esterification
carboxylic acids react with alcohols in the presence of a strong acid catalyst to form esters and water in a condensation reaction
functional group and naming of an ester
COO in the middle of the molecule, the start of the name comes from the alcohol and the second part comes from the carboxylic acid e.g. propanoic acid + ethanol -> ethyl propanoate + water
3 uses of esters
flavourings and perfumes as esters are sweet smelling compounds.
solvents as they are effective at dissolving other organic substances and have a low boiling point.
plasticisers as they enhance flexibility of plastics.
3 methods of synthesising esters
carboxylic acid + alcohol, under reflux with an acid catalyst
acyl chloride + alcohol, at room temp also produces hydrochloric gas
acid anhydrides + alcohols, warm temp also produce a carboxylic acid
2 methods of hydrolysing esters
acid hydrolysis: the ester is heated under reflux with a dilute acid to produce a carboxylic acid and an alcohol.
base hydrolysis: the ester is heated under reflux with a dilute bases to produce a carboxylate salt and an alcohol
differences between fats and oils
fats contain saturated fatty acid chains. no double bonds means there are no kinks in the hydrocarbon chain to allow for tight packing. there are stronger intermolecular forces so are solid at room temp.
oils contain unsaturated fatty acid chains. double bonds causes kinks in the chain preventing close packing of the oil, so they remain liquid due to weak intermolecular forces.
soap
produced when fats and oils are hydrolysed with a strong alkali solution. this reaction breaks the ester bonds in the triglyceride and form glycerol and acid metal salts. the salts make up the soap.
e.g.
fat + sodium hydroxide -> glycerol + sodium salt (soap)
soap has hydrophilic heads which can interact with water but they have hydrophobic tails which interact with the grease.
biodiesel
biodiesel is produced by reacting vegetable oils with methanol in the presence of a potassium hydroxide catalyst. this forms glycerol and methyl esters of fatty acids. CH3OCOR
why is biodiesel used
biodiesel is considered a renewable fuel as it is derived from plant based oils that can be replenished quickly unlike fossil fuels.
acyl chlorides
functional group - COCl
derived from carboxylic acids.
-oyl chloride to the end of the name e.g. methanoyl chloride.
reactions of acyl chloride
(nucelophilic addition elimination)
very reactive due to the polar C=O bond and the -cl is readily displaced.
vigorous reaction with water to reform the carboxylic acid and HCl gas
vigorous reaction at room temp to form an ester and HCl gas
violent reaction at room temp with conc amonia forming a primary amide + HCL gas
violent reaction at room temp with primary amines to form secondary amides and HCL gas
acid anhydride
similar reactivity to acyl chloride. often produce carboxylic acids instead of HCl
duplicate the structure of the carboxylic acid with a joining oxygen
amides
RCONH2 functional group, NH2 instead on the -OH of a carboxylic acid
