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A-level Chemistry: 3.3.8 Aldehydes and Ketones

Chemistry27 CardsCreated 2 months ago

This set of flashcards focuses on carbonyl compounds, specifically aldehydes and ketones. It covers their structures, reactivity with oxidizing agents, and common tests (Tollens’ and Fehling’s) used to identify aldehydes.

Name 2 carbonyl compounds

Aldehydes and ketones

(both contain carbonyl functional group C=O)

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Key Terms

Term
Definition

Name 2 carbonyl compounds

Aldehydes and ketones

(both contain carbonyl functional group C=O)

Draw an aldehyde

Draw a ketone

State which compound reacts with oxidising agents: aldehydes or ketones. Include the product formed.

React with aldehydes to produce carboxylic acids

Name 2 reagents you can use to test for aldehydes

  • Tollens’ reagent

  • Fehling’s solution

What is Tollens’ reagent?

Colourless solution of silver nitrate dissolved in aqueous ammonia

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TermDefinition

Name 2 carbonyl compounds

Aldehydes and ketones

(both contain carbonyl functional group C=O)

Draw an aldehyde

Draw a ketone

State which compound reacts with oxidising agents: aldehydes or ketones. Include the product formed.

React with aldehydes to produce carboxylic acids

Name 2 reagents you can use to test for aldehydes

  • Tollens’ reagent

  • Fehling’s solution

What is Tollens’ reagent?

Colourless solution of silver nitrate dissolved in aqueous ammonia

Describe what happens when Tollens’ reagent is heated in a test tube with an aldehyde

  • Ag+ ions in Tollens’ reagent are reduced to Ag atoms

  • Silver mirror forms

What is Fehling’s solution?

Blue solution of copper(II) ions dissolved in sodium hydroxide

Describe what happens to Fehling’s solution when it’s heated with an aldehyde

Copper(II) ions are reduced to brick-red precipitate of copper(I) oxide

When primary alcohols are oxidised, what products are produced?

Aldehydes and carboxylic acids

(Can use reducing agent to reverse these reactions)

When secondary alcohols are oxidised, what product is produced?

Ketones

(Can use reducing agent to reverse these reactions)

State a reducing agent you can use to reduce aldehydes and ketones

NaBH4 dissolved in water with methanol

In equations, what does the [H] stand for?

Hydrogen from reducing agent

Write an equation showing the reduction of an aldehyde to a primary alcohol. Draw molecules in displayed formula.

Write an equation showing the reduction of a ketone to a secondary alcohol. Draw molecules in displayed formula.

Draw the reaction mechanism for the reduction of an aldehyde to a primary alcohol. Include the name of the reaction mechanism.

Nucleophilic addition

H- ion acts a nucleophile and adds on δ+ on carbon atom

When potassium cyanide reacts with carbonyl compounds, what products are produced?

Hydroxynitriles (molecules with CN and OH)

What type of reaction mechanism occurs when potassium cyanide reacts with carbonyl compounds?

Nucleophilic addition reaction

When potassium cyanide reacts with carbonyl compounds, why it is considered a nucleophilic addition reaction?

∵ nucleophile attacks the molecule & add itself as an extra group

Write an equation for when potassium cyanide dissociates in water


KCN → K+ + CN-

Draw the reaction mechanism for when potassium cyanide reacts with a ketone

Write the overall equation for when potassium cyanide reacts with aldehydes

Write the overall equation for when potassium cyanide reacts with ketones

When you react potassium cyanide with an unsymmetrical ketone or any aldehyde (expect methanal), what will you produce?

Mixture of enantiomers

Describe how potassium cyanide is hazardous

  • Potassium cyanide = irritant & extremely dangerous if ingested or inhaled

  • Can react with moisture to produce hydrogen cyanide = highly toxic gas

State what you can do to reduce the risks of potassium cyanide

Wear gloves, safety goggles and lab coat & perform experiment in fun cupboard

Write the overall equation for the addition of hydrogen cyanide to an aldehyde

RCHO + HCN → RCH(OH)CN