Carboxylic acids and esters Flashcards
Solubility of carboxylic acids?
- COOH group = soluble due to H bonding
- hydrocarbon chain = non-polar
- short chain carboxylic acids = soluble
- long chain carboxylic acids = insoluble
Why do carboxylic acids act as acids?
They donate a proton
Carboxylic acids are weak acids. What does this mean?
Equilibrium lies to the left
How is an ester formed?
Carboxylic acid + alcohol
What catalyst is used in esterification?
H2SO4
3 facts about esterification reactions.
- Water is always a product
- Reversible reaction
- catalyst is H2SO4
What is the name of the reaction that allows esters to be turned back into carboxylic acids and alcohols?
Hydrolysis reaction
What is meant by hydrolysis?
Breaking of a bond using water
What are the two types of hydrolysis?
- Acid catalysed hydrolysis
- Base catalysed hydrolysis
Acid hydrolysis of propylethanoate?
propylethanoate + water —> propan-1-ol + ethanoic acid
catalyst = H2SO4
What is an example of an acid catalyst?
HCl
What is an example of base catalyst?
Warm, aqueous NaOH
In which type of hydrolysis results in high yield of product?
Base hydrolysis
Base hydrolysis of propylethanoate?
propylethanoate + water —> propan-1-ol + ethanoic acid
ethnic acid + NaOH —> Sodium ethanoate
catalyst - NaOH
What is the IUPAC name for glycerol?
propane-1,2,3-triol
What is biodiesel?
Mixture of methyl esters
Uses for esters?
- Plasticisers
- Perfumes
- Flavourings
- Solvents for many reactions
What is an example of an acyl chloride?
ethanoyl chloride CH3COCl
What is an example of an acid anhydride?
ethanoic anhydride
Name CH3CH3COCl
propanoyl chloride
Name CH3CH2CH2CH2CH2COCl
hexanoyl chloride
What functional group is formed when an acyl chloride reacts with water?
Carboxylic acid
What functional group is formed when an acyl chloride reacts with an alcohol?
Ester
What functional group is formed when an acyl chloride reacts with ammonia?
Amide
What functional group is formed when an acyl chloride reacts with an amine?
N-substituted amide
suggest why aqueous ethanol is a suitable solvent when heating the coconut oil with KOH
give a safety precaution when heating the mixture. justify choice
reason
- allows to dissolve both oil and KOH
safety precaution
- use water bath for heating mixture
justification
- prevents risk of fire
why are acylation with acid anhydrides more commonly used than acyl chlorides in industry
- cheaper
- less corrosive
- don’t react with water
- safer side product = carboxylic acid
- acyl chloride produces HCl vapours
describe briefly how you would determine melting point of aspirin
- Sample in capillary / melting point tube
- Heat in melting point apparatus
write equation for reaction between butendioic acid and NaOH
2NaOH + HO2CCHCHCO2H → NaO2CCHCHCO2Na + 2H2O
suggest why only one of two E/Z isomers of butendioic acid can readily form acid anhydride when warmed
- both COOH groups must be on the same side
- no rotation about C=C axis
C = ester
D = carboxylic acid
identify reagent in test tube reaction to distinguish between C and D
reagent = NaHCO3
C observation = no observation
D = effervescence
explain why ethanol chloride can readily react with nucleophiles
- Large charge on carbonyl carbon atom due to bonding to O and Cl
- Nucleophiles have electron pairs which can be donated
one advantage using propanol chloride instead of propanoic acid in lab preparation of methyl propanoate from methanol
- faster/bigger yield/no acid catalyst required
Suggest why an excess of sodium hydroxide is used.
to ensure ester reacts completely
equation for reaction between sodium benzoate and hydrochloric acid
C6H5COONa + HCl → C6H5COOH + NaCl
Suggest two reasons why, in an industrial situation, ethanoic anhydride would be preferred to ethanoyl chloride in the production of paracetamol.
Any two from:
* less exothermic reaction
* easier to control
* dangerous gas not evolved
* ethanoic anhydride is a cheaper or more easily recycled reagent.
