Aldehydes and Ketones Flashcards

Aldehydes and Ketones

A-Level AQA Chemistry

This pack of flashcards covers the chemistry of carbonyls, differentiating between aldehydes and ketones, their solubility, reactions, and tests like Fehling's solution and Tollen's reagent. It includes the oxidation of alcohols, reduction of carbonyls, nucleophilic addition mechanisms, and the use of catalytic hydrogenation and hydrogen cyanide addition, complete with conditions and observations.

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What are carbonyls?	Compounds with a C=O bond, can be aldehydes or ketones.
Describe the difference between aldehydes and ketones.	Aldehydes have the C=O bond at the end of the chain with an H attached, while ketones have the C=O bond in the middle of the chain.
How do smaller carbonyls behave in water?	They are soluble in water because they can form hydrogen bonds with water.
What is the difference between the C=O bond in carbonyls and the C=C bond in alkenes?	The C=O bond is stronger and does not undergo addition reactions easily, while the C=C bond in alkenes attracts electrophiles.
Describe the oxidation of aldehydes.	Aldehydes can be oxidized to carboxylic acids using potassium dichromate (VI) solution and dilute sulfuric acid under reflux.
What are Fehling's solution and Tollen's reagent used for?	They are used as tests for the presence of aldehyde groups.
Define primary alcohol.	An alcohol where the -OH group is attached to a carbon atom that is only bonded to one other carbon atom.
What happens when alcohols are oxidized?	Primary alcohols can be oxidized to aldehydes and then to carboxylic acids, while secondary alcohols can be oxidized to ketones, and tertiary alcohols cannot be oxidized.
Describe the intermolecular forces in carbonyls.	Carbonyls cannot hydrogen bond to themselves, but are attracted by permanent dipole forces.
Describe Tollens' Reagent.	Tollens' Reagent is formed by mixing aqueous ammonia and silver nitrate. It is used to test for aldehydes.
What is the observation when Tollens' Reagent reacts with aldehydes?	With aldehydes, a silver mirror forms coating the inside of the test tube.
What is Fehling's solution used for?	Fehling's solution is used to test for aldehydes. It contains blue Cu2+ ions.
How does Fehling's solution react with aldehydes?	Aldehydes are oxidized by Fehling's solution into a carboxylic acid. The copper (II) ions are reduced to copper(I) oxide.
What happens when aldehydes are reduced using NaBH4 or LiAIH4?	Aldehydes are reduced to primary alcohols.
What happens when ketones are reduced using NaBH4 or LiAIH4?	Ketones are reduced to secondary alcohols.
What is catalytic hydrogenation used for?	Catalytic hydrogenation is another method to reduce carbonyls.
What are the conditions for catalytic hydrogenation?	Catalytic hydrogenation requires high pressure and a hydrogen and nickel catalyst.
Describe the reaction of addition of hydrogen cyanide to carbonyls.	The reaction involves the addition of hydrogen cyanide to carbonyl compounds to form hydroxynitriles.
What reagent is used in the addition of hydrogen cyanide to carbonyls?	Sodium cyanide (NaCN) and dilute sulfuric acid are used as reagents.
What are the conditions required for the addition of hydrogen cyanide to carbonyls?	The reaction occurs at room temperature and pressure.
Explain the mechanism involved in the addition of hydrogen cyanide to carbonyls.	The mechanism is nucleophilic addition, where the nucleophilic CN- ion attacks the carbonyl carbon.
How are hydroxynitriles named?	In the naming of hydroxynitriles, the CN group becomes part of the main chain and is numbered as carbon number 1.
Why is HCN difficult to use for this reaction?	HCN is a toxic gas that is difficult to contain.
What is the result of the addition of HCN to unsymmetrical aldehydes and ketones?	The formation of a racemate occurs, resulting in equal chances of both enantiomers forming.

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