Carboxylic Acid Derivatives Flashcards
What is a derivative of a carboxylic acid?
A compound that can be hydrolysed to form the parent carboxylic acid.
What group is present in carboxylic acids?
Acyl group.
What does an acyl group look like?
An R group bonded to a carbonyl group (C=O) with a functional group attached to the C.
What are 4 derivatives of carboxylic acids?
Ester, acyl chloride, acid anhydride, amide.
How do you name an ester? Example?
Remove the -oic acid suffix from the parent carboxylic acid and replace it with -oate. The alkyl chain attached to the COO group is then added as the first name.
- E.g. methyl ethanoate.
How do you name an acyl chloride? Example?
Remove the -oic acid suffix from the parent carboxylic acid and replace it with -oyl chloride.
- Propanoyl chloride.
How is an acid anhydride formed? Example?
By the removal of water from two carboxylic acid molecules.
- Ethanoic anhydride + H2O.
What 2 products are formed of an acid anydride and a carboxylic acid?
Acid anhydride + H2O.
What is esterification?
The reaction of an alcohol with a carboxylic acid to form an ester.
How is an alcohol prepared to an ester?
The alcohol is warmed with a carboxylic acid with a small amount of conc H2SO4, which acts as a catalyst.
What is the equation of esterification?
Carboxylic acid + Alcohol = Ester + H20 (conc H2SO4 as a catalyst).
What do esters smell like?
Sweet/fruity smells.
How do you make an ester in a laboratory?
- Pour an equal volume of alcohol and carboxylic acid into a boiling tube.
- Add a few drops of c.H2SO4.
- Place boiling tube in a beaker of hot water at 80C.
- Leave boiling tube in water for 5 minutes.
- Pour the contents of the boiling tube into a beaker with aqueous sodium carbonate.
- The NaCO3 is a weak base so neutralises the carboxylic acid in the mixture so removes the smell so the smell of the ester is more distinctive.
What 2 things can ester by hydrolysed by?
- Acid.
- Alkali.
What is hydrolysis?
The chemical breakdown of a compound in the presence of water or in an aqueous solution.
What is acid hydrolysis of an ester the opposite of?
Esterification.
How do you carry out the acid hydrolysis of an ester?
- The ester is heated under reflux with dilute aqueous acid.
- The ester is broken down by water, with the acid acting as a catalyst.
What is the equation for the acid hydrolysis of an ester?
Ester + Water = Carboxylic Acid + Alcohol.
What is alkaline hydrolysis?
Also known as saponification and is irreversible. The ester is heated under reflux with aqueous OH- ions.
What is the equation for the alkaline hydrolysis of an ester?
Ester + OH- = Carboxylate ion + Alcohol.
What is an example of an esterification reaction?
Propanoic acid + Ethanol = Ethyl propanoate + Water.
What is an example of an acid hydrolysis reaction of an ester?
Methyl 2-hydroxybenzoate + Water = 2-hydroxybenzoic acid + Methanol.
What is an example of an alkaline hydrolysis reaction of an ester?
Methyl ethanoate + OH- (aq) = Ethanoate ion + Methanol.
What is the hydroxide ion is a compound in alkaline hydrolysis of an ester? Example?
Metal ester is formed.
- E.g. Sodium ethanoate: CH3COO-Na+.
How are acyl chlorides prepared?
Directly from their parent carboxylic acid by reaction with thionyl chloride, SOCl2. SO2 and HCl are evolved as gases, leaving just the acyl chloride.
Where should acyl chloride reactions be carried out? Why?
In a fume cupboard as the products are harmful.
What is an example of a reaction of an acyl chloride being prepared?
Propanoic acid + SOCl2 = Propanoyl chloride + SO2 (g) + HCl (g).
What is the equation of the reaction of an acyl chloride being prepared?
Carboxylic acid + SOCl2 = Acyl chloride + SO2 (g) + HCl (g).
Why are acyl chloride very useful in chemistry (2)?
- They are very reactive.
- Useful in organic synthesis as they can be easily converted into carboxylic acid derivatives, such as esters and amides, with good yields.
What do acyl chlorides react with? Form?
With nucleophiles by losing the chloride ion whilst retaining the C=O double bond.
What 2 things to acyl chlorides react with to form esters?
- Alcohols.
- Phenols.
What do acyl chlorides react with to form carboxylic acids?
Water.
What do acyl chlorides react with to form amides?
Ammonia and amines.
What is the equation of acyl chlorides with alcohols to form esters?
Acyl chloride + Alcohols = Esters + HCl.
What is an example of an equation of acyl chlorides with alcohols to form esters?
Ethanoyl chloride + Propan-1-ol = Propyl ethanoate + HCl.
What is the equation of acyl chlorides with phenols to form esters?
Acyl chloride + Phenol = Phenyl ester + HCl.
Why are acyl chlorides used to form esters with phenols?
Because carboxylic acids are not reactive enough to form esters with phenols. Acyl chlorides and acid anhydrides are both more reactive than carboxylic acids and react with phenols to produce phenyl esters. Neither reactions needs a catalyst.
What is an example of an equation of acyl chlorides with phenols to form esters?
Ethanoyl chloride + Phenol = Phenyl ethanoate + HCl.
What is the equation of acyl chlorides with water to form carboxylic acids? Type of reaction?
Acyl chloride + Water = Carboxylic acid + HCl.
- Reacts vigorously.
What is an example of an equation of acyl chlorides with water to form carboxylic acids?
Ethanoyl chloride + Water = Ethanoic acid + HCl.
What is observed when ethanoyl chloride reacts with water?
Steamy fumes of HCl are observed.
How does ammonia and amines react with acyl chlorides?
Ammonia and amines can act as nucleophiles by donating the lone pair of electrons on the nitrogen atom to an electron-deficient species.
What is formed when ammonia reacts with acyl chlorides?
A primary amide.
How can you identify a primary amide?
In the primary amide the nitrogen atom is attached to one carbon.
What is the equation when ammonia reacts with acyl chlorides to form primary amides?
Acyl chloride + Ammonia = Primary amide + Ammonium chloride.
What is an example of a reaction when ammonia reacts with acyl chlorides to form primary amides?
Ethanoyl chloride + 2NH3 = Ethanamide + NH4Cl.
What is formed when primary amines react with acyl chlorides?
A secondary amide.
How can you identify a secondary amide?
In the secondary amide the nitrogen atom is attached to two carbon.
What is the equation when a primary amine reacts with acyl chlorides to form secondary amides?
Acyl chloride + Primary amine = Secondary amide + Ammonium chloride.
What is an example of a reaction when a primary amine reacts with acyl chlorides to form secondary amides?
Ethanoyl chloride + Methylamine = N-methanamide + methylammonium ion.
What is the equation for an acid anhydride and phenol?
Acid anhydride + Phenol = Phenyl ester + Carboxylic Acid.
What is an example of a reaction for an acid anhydride and a phenol?
Ethanoic anhydride + Phenol = Phenyl ethanoate + Ethanoic acid.
What is the difference in reactivity between acid anhydrides and acyl chlorides? Useful?
Acid anhydrides are less reactive than acyl chlorides and are useful in laboratory experiments where acyl chlorides may be too reactive.
What is the mechanism of nucleophilic addition - elimination? (2)?
- Addition: lone pair of electrons from nucleophile is attracted and donated to the positive carbon in the C=O group of the acyl chloride. A dative covalent bond is formed between the nucleophile and the carbonyl carbon atom. The Pi bond of the C=O group breaks, forming a negatively charged intermediate.
- Elimination: lone pair of electrons on the oxygen reforms the C=O double bond, causing a chloride ion to be removed. A proton is also then lost to complete the elimination.
