6.1.3 - Carboxylic acids and esters Flashcards
Give properties of carboxylic acids
- weak acids
- soluble up to 4 carbons
- as carbon no. increases, solubility decreases because non-polar chain has greater effect on overall molecule polarity
- dicarboxylic acids dissolve readily in water and are solids at room temp
Give the carboxylic acid derivatives and their functional groups
ester R-COOR
acyl chloride R-COCl
acid anhydride R-COOC(R)O
amide R-CONH2
How to name an ester
–thyl from alcohol
–oate from carboxylic acid
How to make an ester in a lab
- use equal volumes of carboxylic acid and alcohol then add a few drops conc H2SO4
- place tube in 80°C water for 5 mins
- pour into beaker with Na2CO3 (aq) (neutralises any remaining acid)
Uses of esters
- perfumes
- flavourings
Preparing acyl chlorides
carboxylic acid + SOCl2 -> acyl chloride + SO2 + HCl
Esterification of carboxylic acids
carboxylic acid + alcohol -> ester + H2O
Esterification of acyl chloride (irreversible)
acyl chloride + alcohol -> ester + HCl
Acyl chloride/acid anhydride + phenol
ester + HCl
Why are acid anhydrides often used instead of acyl chlorides?
react in same way but don’t produce toxic products and reactions are typically more controlled
Making an acid anhydride
2 carboxylic acids -> acid anhydride + H2O
Acyl chloride -> carboxylic acid
acyl chloride + H2O -> carboxylic acid
Forming a primary amide
acyl chloride + 2NH3 -> primary amide + NH4Cl
Forming a secondary amide
acyl chloride + primary amine -> secondary amide + CH3NH3+Cl-
Ester hydrolysis
ester + H2O ⇌ carboxylic acid + alcohol
- heated under reflux with dilute H+
ester + base -> carboxylate salt + alcohol
- heated under reflux with OH- ions
