10: Carboxylic Acids And Their Derivatives Flashcards
Why do carboxylic acids have quite high boiling points
They can form hydrogen bonds
Why is the boiling point of a carboxylic acid higher than an alcohol
- The O-H bond in a carboxylic acid is even more polar than in an alcohol because of the adjacent C=O group.
- Carboxylics acids have a molecular structure that enables them to form more hydrogen bonds than simple alcohols
Are carboxylic acids soluble in water
Yes, especially smaller carboxylic acids
Why does the solubility of a carboxylic acid decrease when the molecule gets bigger
Only the O-H group can form hydgrogen bonds with water so if the rest of the molecule is large and non-polar then it will be less soluble
How to prepare a carboxylic acid
Oxidation of a primary alcohol or and aldehyde
What are the reagents and conditions for oxidation of a primary alcohol or aldehyde
Acidified potassium dichromate, heat and under reflux
Write alcohols, carboxylic acids and phenols in order of acidity
Alcohol (not acidic)
Phenols (very weakly acidic)
Carboxylic acids (weakly acidic)
What does carboxylic acid + metal produce
Salt + hydrogen
What does carboxylic acid + carbonate produce
Salt + carbon dioxide + water
What does carboxylic acid + alkali produce
Salt + water
What does carboxylic acid + ammonia produce
Ammonium salt
Can esters form hydrogen bonds
No
How to produce an ester
Carboxylic acid + alcohol —> ester + water
What is a condensation reaction
Two molecules are joined together to make a larger product molecule but a small molecule is eliminated in the process
What conditions are needed for esterification
Concentrated sulphuric acid catalyst and heat.
Works best with reflux
What is an acid anhydride
Compound formed by dehydration of carboxylic acids.
What is the general formula for acid anhydrides
R-COOCO-R
How is an acid anhydride formed
two carboxylic acids bond together and eliminate the OH from one and the H from the -OH from the other carboxylic acid to form an acid anhydride and water
What does acid anhydride + alcohol form
ester + carboxylic acid
What are the advantages of using anhydrides rather than carboxylic acids for producing esters
Anhydrides are more reactive which means:
Milder conditions can be used,
The reaction is irreversible which means that a higher percentage yield can be achieved
What does hydrolysis of an ester produce
carboxylic acid and alcohol
Why would you not just use water for hydrolysis of an ester and what can you use instead
It is extremely slow,
An acid or a base
Base is usually preferred
What does base catalysed hydrolysis of ester produce
Alcohol and the salt of the carboxylic acid (due to the alkaline conditions)
What are the conditions for base catalysed hydrolysis of esters
Aqueous NaOH and under reflux
How to convert the salt formed from the base - catalysed hydrolysis of an ester back into a carboxylic acid
Neutralise with aqueous acid to convert the salt into the carboxylic acid
Distil off the carboxylic acid
What are the conditions for acid catalysed hydrolysis of esters
Reflux the ester with aqueous HCl
What is the general form of an acyl chloride
RCOCl
How to name acyl chlorides
Add the ending -oyl chloride
eg. CH₃COCl is ethanoyl chloride
What is added to a carboxylic to form an acyl chloride
thionyl chloride, SOCl₂
Advantages of using acyl chlorides instead of esterifying the carboxylic acid
The reaction occurs rapidly, without a catalyst and without heating
Generally high yield
Can be used to esterify phenols
How can acyl chlorides be converted into carboxylic acids
Reacting with water
How can acyl chlorides react with Aromatic compounds
Friedel-Crafts
In the presence of a halogen carrier catalyst, the acyl group of an acyl chloride can substitute into an aromatic ring
What does acyl chloride + ammonia produce
Amides
