Chapter 26 - Carbonyls and carboxylic acids Flashcards
What is the carbonyl functional group?
C=O
What is the aldehyde group? (-al)
CHO
What is the ketone group? (-one)
CO
What product is made when you oxidise an aldehyde?
Carboxylic acid
How do you oxidise an aldehyde?
Reflux with acidified dichromate ions and sulfuric acid
What is the reactivity of aldehydes and ketones influenced by?
The nature of the carbon - oxygen double bond
What reaction can carbonyl groups undergo?
Nucleophilic addition
How does a nucleophile react with a carbonyl?
The nucleophile is attracted to and attacks the slightly positive carbon atom, resulting in addition across the C=O bond
What happens when you reduce an aldehyde?
A primary alcohol is made
What happens when you reduce a ketone?
A secondary alcohol is made
What do you use in the reduction of a carbonyl?
NaBH4, water and heat
How are oxidation agents represented in an equation?
[O]
How are reduction agents represented in an equation?
[H]
What is produced when an aldehyde is reduced using HCN?
A hydroxynitrile (with a CN triple bond)
What is HCN?
Hydrogen cyanide is a poisonous liquid which can is used as a means of increasing the length of the carbon chain
What are the two catalysts in a HCN reduction reaction?
H2SO4 and NaCN
What is used to detect the presence of the carbonyl functional group?
Brady’s reagent (clear to orange)
What can be used to distinguish between an aldehyde and a ketone after identifying a carbonyl group?
Tollen’s reagent (solution of silver nitrate in aqueous ammonia) which forms a silver mirror precipitate with the presence of an aldehyde group
What is a carboxyl functional group?
A carbonyl group and a hydroxyl group
Which carbon atom is a carboxyl group designated to?
Carbon-1
Describe the solubility of carboxylic acids
- C=O and O-H bonds are polar and so they dissolve in water
- As the number of carbon atoms increases, the solubility decreases (non-polar chain has a greater effect on the overall polarity of the molecule)
What kind of acid is a carboxylic acid?
Weak acids
What reactions do carboxylic acids take part in?
Neutralisation (with bases/ alkalis, metal oxides, carbonates) and redox (with metals)
What happens to the suffix of a carboxylic acid when it reacts?
-ic acid becomes -ate (carboxylic to carboxylate)
What happens when a carboxylic acid reacts with metals in a redox reaction?
A carboxylate salt and hydrogen gas is produced (metal disappears and effervescence produced)
What happens when a carboxylic acid reacts with a metal oxide?
A salt and water is produced
What happens when a carboxylic acid reacts with an alkali?
A salt and water is produced (H+ + OH- > H2O)
What happens when a carboxylic acid reacts with a carbonate?
A salt, water and carbon dioxide is produced
What is a derivative of a carboxylic acid?
A compound that can be hydrolysed to form the parent carboxylic acid
What is present in carboxylic acid derivatives?
An acyl group (common sequence of atoms in their sequence)
Give some examples of carboxylic acid derivatives
Esters, acyl chlorides, acid anhydrides and amides
What happens when a carboxylic acid becomes an ester?
The hydrogen of OH is removed and replaced by another element (eg. Cl/ Br)
What happens when two carboxylic acids react?
They form an acid anhydride aswell as H2O
What is esterification?
The reaction between alcohol and a carboxylic acid to form an ester and water
What is required for esterification to occur?
Warm temperatures and concentrated H2SO4 (catalyst)
How can you change an ester into a carboxylic acid?
Acid hydrolysis by heating an ester under reflux with dilute aqueous acid
What are the products of acid hydrolysis?
A carboxylic acid and an alcohol
