OCR A-Level Chemistry: Chapter 26 - Carbonyls and Carboxylic Acids
This flashcard set identifies the carbonyl group (C=O), outlines oxidation conditions for aldehydes using acidified potassium dichromate under reflux, and describes the use of Brady’s reagent (2,4-DNPH) to detect carbonyls through crystal formation.
What is the carbonyl functional group?
C=O
Key Terms
What is the carbonyl functional group?
C=O
What is the reaction condition and reactants for oxidation of aldehydes?
In reflux
K2Cr2O7
H2SO4
Outline the detection of a carbonyl using Brady’s reagent
Add 5cm depth of 2,4 DNPH (Brady’s reagent)
Use a pipette to add three drops of unknown
If no crystals form, add a...
Which reagent can distinguish between an aldehyde and a ketone?
Tollen’s reagent
How does Tollen’s reagent distinguish between an aldehyde and a ketone?
Aldehyde group present
Silver mirror produced
Ketone group present
No silver mirror produced
How does Fehling’s reagent distinguish between an aldehyde and ketone?
Aldehyde group present
Brick red precipitate formed
Ketone group present
Stays blue/no change
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| Term | Definition |
|---|---|
What is the carbonyl functional group? | C=O |
What is the reaction condition and reactants for oxidation of aldehydes? | In reflux |
Outline the detection of a carbonyl using Brady’s reagent | Add 5cm depth of 2,4 DNPH (Brady’s reagent) |
Which reagent can distinguish between an aldehyde and a ketone? | Tollen’s reagent |
How does Tollen’s reagent distinguish between an aldehyde and a ketone? | Aldehyde group present |
How does Fehling’s reagent distinguish between an aldehyde and ketone? | Aldehyde group present |
Outline nucleophilic addition with a carbonyl and cyanide ion | Negative charge cyanide Lone pair from C=O to O Lone pair from -CN to C O- lone pair to H on HCN Lone pair in H-C to C in CN OH formed Nitrile formed |
How can acidified potassium dichromate distinguish between aldehydes and ketones? | Aldehyde present |
Why is potassium cyanide used instead of hydrogen cyanide? | It’s safer |
Name the four carboxylic acid derivatives | Ester |
What is the suffix for an acyl chloride? |
|
What is the suffix for an acid anhydride? | -oic anhydride |
When an acid anhydride reacts with a nucleophile, what are the two products? | R-CONu R-COO- |
What is the characteristic mechanism to change an acyl chloride to a carboxylic acid? | Addition-Elimination |
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Outline process of acid hydrolysis of an ester | Ester heated under reflux with dilute aqueous acid Ester broken down by water into carboxylic acid and alcohol |
Outline process of alkaline hydrolysis of an ester | Ester heated under reflux with aqueous hydroxide ions Ester broken down by water into carboxylate ion and alcohol |