Carboxylic acids and derivitives Flashcards
what is the suffix for carboxylic acids
-oic acid
can be en or an
what is the carboxylic acid functional group
COOH
describe the solubility of carboxylic acids
Carboxylic acids are more soluble in water than their equivilent aldehyde or alcohol because they can form multiple hydrogen bonds with water.
via the H in their OH and from the lone pairs of e⁻ from their =O
state and explain the trend in solubility along the homologuous series
water solubility decreases as the number of carbon atoms in the chain increases as hydrocarbons can only form london forces not hydrogen bonds.
What are the reactions of carboxylic acid
- As an H⁺ donor (as an acid)
- to make esters
what is the strength of a carboxylic acid
it is a weak acid
what type of acid reactions do carboxylic acids undergo
- redox reactions with metals
- neutralisation reactions with bases ( alkalis, oxides, carbonates)
what does acid reactions of carboxylic acids produce
carboxylic acids from carboxylate salts which are ionic compounds.
The complex anion is named after the carboxylic acid e.g. methanoic acid forms methanoate salts.
what do redox reactions of carboxylic acids with salts produce
carboxylate salt + hydrogen
what do neutralisation reactions with carboxylic acids and metal oxides produce
carboxylate salt + water
what do neutralisation reactions with carboxylic acids and alkalis produce
carboxylate salt + water
what do neutralisation reactions with carboxylic acids and carbonates produce
carboxylate salt + CO₂ + water
How do carboxylic acids react to form esters
The reaction between carboxylic acid and an alcohol gives an ester. A catalytic amount of H⁺ from a strong acid (e.g. H₂SO₄) is required.
It is an equilibrium reaction so to produce more of the ester the water which is also produced in the reaction should be removed, to push equilibrium to the right.
what is the functional group of esters
COOC
Describe the solubility of esters
Esters contain a permenant dipole between C=O but a limited ability to form hydrogen bonds with water. They are held together by permenant dipole-dipole interactions.
Esters are therefore insoluble in water.
describe how esters are named
The name comes from the alcohol and the acid which forms the ester.
The format is:
(carbon chain in the alcohol)yl (carbon chain in the acid)**oate)
why is the reaction of a carboxylic acid and an alcohol not always favoured and what is the alternative(s)
The reaction of an acid and an alcohol is an equilibrium and therefore a 100% yeild cannot be obtained.
The reactions of acid anhydride or acyl chlorides with alcohols provide a better alternative.
describe how an acid anhydride is formed
an acid anhydride is formed when two acids react and eliminate water
describe the process of making ethyl propanoate
- add 2cm³ of ethanol and 2cm³ of propanoic acid into a boiling tube
- add drops of sulfuric acid
- place boiling tube in an 80℃ water bath and leave for 5mins.
- pour the boiling tube into a beaker containing NaOH to neutralise the acid
define hydrolysis
hydrolysis is the chemical breakdown of a compoind in the presence of water or in aqueous solutions.
define esterificaiton
esterification is the reaction of an alcohol with a carboxylic acid to form an ester
What is the acid hydrolysis of an ester
acid hydrolysis of an ester is the opposite of esterification
Describe what is carried out in acid hydrolysis esters
The ester is heated under reflux with dilute aqueous acid.
The ester is broken down by water, with the acid acting as a catalyst.
This is reversable
Describe what is carried out in alkali hydrolysis of esters
Alkali hydrolysis is irreversible.
The acid is heated under reflux with NaOH (or aqueous hydroxide ions)
This produces a carboxylate salt and an alcohol
How do you regain the carboxylic acid from a carboxylate salt
add a strong acid
How do you from acyl chlorides
add SOCl₂ to their parent carboxylic acid.
The reaction shoudl be carried out in a fume cupboard as it priduces SO₂ and HCl as gases which are harmful
what are the reactions of acyl chlorides
- with alcohols to form esters
- with phenols to form esters
- with water to form carboxylic acids
- with ammonia and amines to form amides.
is a catalyst required for the reaction of acyl chlorides or acid anhydrides with phenols to form esters
No, they are more reactive than carboxylic acids
why are acyl chlorides so useful
they are very reactive and can easily be converted into esters, carboxylic acids, amides with good yeilds.
They react with nucleophiles by losing the chloride ion whilst retaining the C=O.
describe the reaction of ammonia and amines reacting with acyl chlorides
ammonia and amines can act as nucleophiles by donating the lone pair of electrons on th enitrogen to an electron deficient species.
The reaction with acyl chlorides forms amides.
Ammonia reacts with acyl chlorides to form a primary amide, here the nirtogen is attached to one carbon atom.
what is the relative reactivity of acid anhydrides to acyl chlorides
acid anhydrides are less reactive than acyl chlorides but react in a similar way to acyl chlorides with alcohol, phenol, water, ammonia, and amines.
