Part 1 – Testing for Alcohols

• Add 1ml of Ethanol to a clean, dry test tube

• Very carefully add a small piece of metallic Sodium

• Record your observations in a suitable table

In the presence of a functional alcohol group the Sodium will react, the student will observe the metal Sodium fizzing with bubbles of Hydrogen gas being released

2C₂H₅OH + 2Na → CH₃CH₂Ona + H₂

Part 2 – Testing for Aldehyde using Fehling’s solution

• Add 2mls of Fehling's solution A and Fehling's solution B into a clean, dry test tube, and shake to mix. The solution should be a clear dark blue solution

• To a separate test tube add 1ml of Sodium Carbonate solution and some Anti bumping granules, add 5 drops of the prepared solution from step one

• To the same test tube add 1ml of Ethanal

• Warm the test tube gently for around 2 minutes in a beaker that is half filled with hot water

• Gradually bring the beaker of water to boiling and maintain the water bath at this temperature for a few minutes (CLEAPSS advice: stand test tube in a beaker of just boiled water from a kettle, instead of using a Bunsen Burner)

• Using a test tube holder remove the test tube from the water bath. Allow the solution to cool for several minutes and observe and record the results in a suitable table.

• A positive test will give a brick red precipitate

Fehling’s reagent is Copper (II) complex made by adding two solutions together:

Fehling’s solution A – contains Copper (II) Sulfate Fehling’s

solution B – contains Sodium Hydroxide and Potassium Sodium Tartrate

When the mixture is warmed with an aldehyde, the brick red precipitate is Copper (I) Oxide which is formed as the Copper (II) is reduced to Copper (I)

CH₃CHO+ 2Cu²⁺ + SOH^- → CH₃COO^- + CU₂O + 3H₂0
(Fehling’s A)         (Fehling’s B)   (insoluble ppt)

Part 3 – Test for an Alkene (a test for unsaturation)

• Add 2 drops of Cyclohexene to a test tube

• Add 1ml of Bromine water to the same test tube and shake the contents to mix well

• Observe and record results in a suitable table

• A positive result will see the Bromine water change from the orange/red colour to colourless

An unsaturated organic molecule contains a C=C double bond. When Bromine water is added the double bond opens up and a dibromide is formed

C₆H₁₀ + Br₂ → C₆H₁₀Br₂

Part 4 – Testing for Carboxylic Acid

• Add 2 drops of Cyclohexene to a test tube

• Place a spatula of Sodium Hydrogen Carbonate in a boiling tube

• Add 2mls of dilute Ethanoic Acid to the same boiling tube

• Observe and record your results

Students will observe bubbles in the solution as carbon dioxide is formed as the Ethanoic Acid reacts with the Sodium Hydrogen Carbonate

CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

Part 5 – Testing for a Haloalkane

• To a clean, dry test tube add 1ml of Sodium Hydroxide solution

• Using a pipette add 5 drops of 1-Bromobutane

• Warm the test tube by placing in a beaker filled with warm water (around 60⁰C) and leave for a few minutes

• Acidify the solution by adding 2mls of dilute Nitric Acid, followed by 1ml of Silver Nitrate solution

• Observe and record your results in a suitable table

With a positive result students will observe the formation of a very pale cream precipitate when the Sodium Hydroxide is added, the halogen (Br) atom from the Haloalkane is displaced as a Halide ion

C₄H₉Br + NaOH → C₄H₉OH + NaBr

As an ionic equation:

C₄H₉Br + OH^- → C₄H₉OH + Br^-

Acidifying this reaction ensures that any unreacted Hydroxide ions do not react with the Silver ions to give a confusing result with precipitate

Addition of Silver Nitrate allows the Halogen ion (Br¯) to react with the Silver ion to form an insoluble Silver Bromide precipitate

AgNO₃ + NaBr → AgBr + NaNO₃