CP6 Testing for Organic Functional Groups

• What are organic functional groups?

  Specific groups of atoms
• Organic functional groups determine the chemical properties and reactivity
• What is the formula for an alkene functional group?

  -C=C-
• What is an example of a molecule with an alcohol functional group?

  Ethanol
• What is the formula for a ketone functional group?

  -C(=O)-
• Alkenes react with bromine in an addition
• Bromine water decolourises when reacted with an alkene.
• What is the chemical equation for the reaction of an alkene with bromine?

  C=C + Br_2 → Br-C-C-Br</latex>
• Match the functional group with its example:

  Alcohol ↔️ Ethanol

  Aldehyde ↔️ Formaldehyde

  Ketone ↔️ Acetone

  Carboxylic acid ↔️ Acetic acid
• Steps in the test for alkenes

  1️⃣ Add bromine water

  2️⃣ Observe decolourisation

  3️⃣ Note the addition reaction
• Alkenes react with bromine in an addition reaction.
• What reagent is used to test for alkenes?

  Bromine water
• Alkenes are tested using bromine water.
• The reaction between alkenes and bromine water is an addition reaction.
• The bromine water changes from orange to colourless when it reacts with an alkene.
• The chemical equation for the reaction between alkenes and bromine water is $C =$$C +$$Br_{2(aq)} → Br - C - C - Br$
• Alcohols can be tested using oxidizing agents such as potassium dichromate or potassium permanganate.
• Potassium dichromate turns orange to green when it reacts with alcohols.
• Aldehydes react with Tollens' reagent to form a silver mirror.
• Fehling's solution forms a red precipitate with aldehydes.
• Functional groups determine the chemical properties and reactivity of organic molecules.
• The test for alkenes uses bromine water.
• The double bond in alkenes reacts with bromine water to decolourise it.
• What is the purpose of understanding functional groups in organic chemistry?

  Predict compound behavior
• What is the example of an alcohol listed in the table?

  Ethanol
• The test for alkenes involves reaction with bromine water
• Bromine water decolourises in the presence of an alkene due to an addition reaction.
• What is the chemical equation for the reaction of an alkene with bromine water?

  $C =$$C +$$Br_{2(aq)} → Br - C - C - Br$
• Alcohols can be oxidized using potassium dichromate, which changes from orange to green.
• Ethanol, when oxidized by potassium dichromate, first forms acetaldehyde
• What functional group is present in both aldehydes and ketones?

  Carbonyl
• Match the reagent with its observation and reaction for aldehydes and ketones:

  Tollens' reagent ↔️ Silver mirror formation ||| Oxidation of aldehydes to carboxylic acids

  Fehling's solution ↔️ Red precipitate formation ||| Oxidation of aldehydes to carboxylic acids

  Brady's reagent ↔️ Yellow/orange precipitate formation ||| Formation of hydrazones
• Carboxylic acids produce carbon dioxide gas when reacted with carbonates.
• Bubbling or effervescence in the reaction of a carboxylic acid with a carbonate indicates the release of carbon dioxide
• What is the chemical equation for the reaction of a carboxylic acid with sodium carbonate?

  2R - COOH + Na_{2}CO_{3} → 2R - COONa + CO_{2} + H_{2}O</latex>
• Ethanoic acid produces carbon dioxide gas when reacted with sodium carbonate.
• What gas is produced when carboxylic acids react with carbonates?

  Carbon dioxide
• When carboxylic acids react with carbonates, the observation is bubbling or effervescence
• Ethanoic acid reacts with sodium carbonate to produce carbon dioxide gas.
• What reagent is used to test for amines?

  Hydrochloric acid