Back to AI Flashcard MakerChemistry /OCR A-Level Chemistry: Chapter 26 - Carbonyls and Carboxylic Acids

OCR A-Level Chemistry: Chapter 26 - Carbonyls and Carboxylic Acids

Chemistry17 CardsCreated 2 months ago

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

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Key Terms

Term
Definition

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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TermDefinition

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 few drops of sulphuric acid
A yellow/orange precipitate indicates carbonyl presence

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

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
Orange solution to green
Ketone present
No change to solution

Why is potassium cyanide used instead of hydrogen cyanide?

It’s safer

Name the four carboxylic acid derivatives

Ester
Acyl chloride
Acid anhydride
Amide

What is the suffix for an acyl chloride?


-oyl 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


Describe esterification


Alcohol + carboxylic acid with conc sulfurated acid

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