6.1.2 Carbonyl compounds Flashcards
(15 cards)
What reagent is used to oxidise aldehydes to carboxylic acids?
Potassium dichromate (K2Cr2O7) in dilute sulfuric acid (H2SO4); [O] used in equations.
What is the role of [O] in redox reactions involving aldehydes?
It represents an oxidising agent, used to show the gain of oxygen or loss of hydrogen in reactions.
What type of reaction occurs when NaBH4 is used with carbonyl compounds?
Nucleophilic addition, reducing aldehydes and ketones to alcohols.
What is the nucleophile in the reaction between NaBH4 and carbonyl compounds?
Hydride ion (H–).
What occurs after the nucleophilic addition of NaBH4 to a carbonyl compound?
Protonation of the organic intermediate by water (H2O).
What is the role of HCN in reactions with aldehydes and ketones?
It forms hydroxynitriles through nucleophilic addition.
What is the initial nucleophile in the reaction between HCN and a carbonyl compound?
Cyanide ion (CN–).
What happens in the second stage of the reaction between HCN and a carbonyl compound?
Protonation by water (H2O) or H+.
What does 2,4-dinitrophenylhydrazine (2,4-DNPH) test for?
The presence of a carbonyl group in an organic compound.
How can a carbonyl compound be identified after reaction with 2,4-DNPH?
By measuring the melting point of the derivative formed.
What is Tollens’ reagent composed of?
Tollens’ reagent formed by mixing aqueous ammonia and silver nitrate
What does Tollens’ reagent test for?
The presence of an aldehyde group.
How does Tollens’ reagent distinguish between aldehydes and ketones?
Aldehydes are oxidised to carboxylic acids, reducing silver ions (Ag+) to metallic silver (Ag).
What observable result indicates a positive Tollens’ test?
A silver mirror forms on the inner surface of the test tube.
In equations involving Tollens’ reagent, what symbol can be used to represent the oxidising agent?
[O] is acceptable.
