Carboxylic Acids and Esters
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What is the functional group of a carboxylic acid?
COOH
How are carboxylic acids formed?
Oxidation of primary alcohols under reflux.
Describe the kind of acids carboxylic acids are.
Weak acids that slightly dissociate when in solution forming a H+ ion and a carboxylate ion RCOO-.
What do carboxylic acids form when they react with carbonates?
A carboxylate salt, water and carbon dioxide.
Describe the solubility of carboxylic acids.
Small chain carboxylic acids are able to form hydrogen bonds with water molecules between the lone pair on the oxygen atom and the S+ on the hydrogen atom. This makes them soluble in water.
How are esters formed?
Carboxylic acids react with alcohols in the presence of a strong catalyst to form esters. This is called esterification and is done under reflux.
What are esters used in?
Perfumes and food flavouring.
Describe esters.
Low boiling points and make good solvents for other polar molecules. Volatile.
What is biodiesel?
An ester produced from vegetable oils and methanol in the presence of a strong acid catalyst.
What is ester hydrolysis?
Reverse reaction to esterification where esters are converted back into alcohols and carboxylic acids. This is done by adding water but can be carried out under different conditions to produce different products.
What do u form when an ester reacts with a base (e.g. NaOH) ?
Carboxylate salt and an alcohol
What is the production of a carboxylate salt called?
Saponification
What are carboxylate salts commonly used as? Why?
Soaps since they have both hydrophobic and hydrophilic properties.
When are acid anhydrides formed?
When water is removed from 2 carboxylic acids.
What is formed when an acyl chloride reacts with a water?
Carboxylic acid
What is formed when an acyl chloride reacts with an alcohol?
Ester
What is formed when an acyl chloride reacts with ammonia?
Amide
What is formed when an acyl chloride reacts with amine?
N-substituted amide.
What is aspirin?
An ester produced from salicylic acid and ethanoic anhydride.
Why isn’t ethanoyl chloride used in the production of aspirin?
It is expensive and produces harmful HCl fumes as part of the reaction. Thus ethanoic anhydride is much safer.
How do you distinguish carboxylic acids from other -OH containing compounds?
Add NaHCO3. Acids will produce sodium salt, water and carbon dioxide. Effervescence due to carbon dioxide formation. Bubble gas through limewater which turns cloudy to confirm it is carbon dioxide.
What catalyst is needed for the formation of esters from alcohols and carboxylic acids?
Concentrated strong acid e.g. H2SO4
What catalyst is needed for the hydrolysis of esters?
Dilute strong acid e.g. H2SO4
What is an alternative method of hydrolysis?
Base hydrolysis