6.1.3 - Carboxylic acids and esters Flashcards
Give the 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 do you name an ester?
–thyl from alcohol
–oate from carboxylic acid
How can you 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)
Name 2 uses of esters
- perfumes
- flavourings
Describe how to prepare an acyl chloride
carboxylic acid + SOCl2 -> acyl chloride + SO2 + HCl
Describe the esterification of carboxylic acids
carboxylic acid + alcohol -> ester + H2O
Describe the esterification of acyl chloride (irreversible)
acyl chloride + alcohol -> ester + HCl
What are the products of: 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
How do you make an acid anhydride?
2 carboxylic acids -> acid anhydride + H2O
How to convert an acyl chloride -> carboxylic acid?
acyl chloride + H2O -> carboxylic acid
How can you form a primary amide?
acyl chloride + 2NH3 -> primary amide + NH4Cl
How do you form a secondary amide?
acyl chloride + primary amine -> secondary amide + CH3NH3+Cl-
Describe how esters can be hydrolysed
ester + H2O ⇌ carboxylic acid + alcohol
- hot (aq) acid catalyst
ester + base -> carboxylate salt + alcohol
- hot (aq) alkali reagent
Describe the reaction of an acid anhydride with an alcohol
acid anhydride + alcohol -> ester + carboxylic acid
