3.3.8.3 Tests for Aldehydes and Ketones

• Where is the carbonyl group located in aldehydes?

  At the end of the chain
• Aldehydes are more reactive than ketones due to the position of the carbonyl group


  True
• Ketones react with Tollens' reagent to form a silver mirror

  False
• Ketones react with Fehling's solution to form a precipitate

  False
• Aldehydes and ketones are both carbonyl compounds.


  True
• Match the compound with its type:

  Acetaldehyde ↔️ Aldehyde

  Acetone ↔️ Ketone
• Steps of the reaction between Tollens' reagent and an aldehyde

  1️⃣ Tollens' reagent reacts with the aldehyde

  2️⃣ The aldehyde is oxidized to a carboxylic acid

  3️⃣ Silver ions (Ag⁺) are reduced to metallic silver (Ag)

  4️⃣ A silver mirror forms on the test tube
• What precipitate is formed when Fehling's solution reacts with an aldehyde?

  Red-orange precipitate
• What type of precipitate is formed when Brady's reagent reacts with an aldehyde or ketone?

  Yellow-orange precipitate
• How can you identify a ketone based on chemical test results?

  Forms yellow-orange precipitate with Brady's only
• What is Tollens' reagent used for?

  To distinguish aldehydes
• What is Fehling's solution composed of?

  Copper(II) sulfate and NaOH
• Why are aldehydes more reactive than ketones?

  Carbonyl group at the end
• In aldehydes, the carbonyl group is located at the end of the chain
• Aldehydes are more susceptible to oxidation due to the carbonyl group being at the end
• Why do ketones not react with Tollens' reagent?

  Lack of easily oxidizable hydrogen
• Ketones react with Fehling's solution to form a red-orange precipitate.

  False
• Brady's reagent can detect both aldehydes and ketones.


  True
• Aldehydes and ketones are both carbonyl compounds, meaning they contain a carbon-oxygen double bond
• The general formula for aldehydes is RCHO
• Steps in the reaction of Tollens' reagent with an aldehyde

  1️⃣ Silver ions in Tollens' reagent are reduced

  2️⃣ Metallic silver forms a silver mirror

  3️⃣ The aldehyde is oxidized to a carboxylic acid
• When Fehling's solution reacts with an aldehyde, a red/orange precipitate of copper(I) oxide is formed.
• Why is the carbonyl group in aldehydes more reactive compared to ketones?

  It is at the end of the chain
• What is the general formula for ketones?

  $R_{1}COR_{2}$
• What is Tollens' reagent prepared from?

  Silver nitrate and ammonia
• Fehling's solution is composed of copper(II) sulfate and sodium hydroxide
• Brady's reagent is also known as 2,4-dinitrophenylhydrazine
• Match the reagent with the observed reaction with aldehydes:

  Tollens' Reagent ↔️ Forms a silver mirror

  Fehling's Solution ↔️ Forms a red-orange precipitate

  Brady's Reagent ↔️ Forms a yellow-orange precipitate