Beilstein Test for Halogens

Detecting halogen atoms in organic compounds using a copper wire flame test

Qualitative Analysis Beginner (Middle School) 25 min ~$5.00

Objective

Determine whether an organic compound contains halogen atoms (Cl, Br, I) using the Beilstein copper wire test.

Background

The Beilstein test is a simple qualitative test for halogens in organic compounds. A copper wire is heated in a flame to form copper(II) oxide, then dipped in the test substance and returned to the flame. If a halogen is present, volatile copper halide forms and imparts a green or blue-green color to the flame. The test is sensitive but not specific (it does not distinguish between Cl, Br, and I, and can give false positives with some nitrogen compounds).

Safety Warnings

  • Chloroform is toxic — avoid inhalation and skin contact
  • Work in a fume hood when testing volatile organics
  • Hot copper wire can cause burns
  • Keep flammable solvents away from the flame

Required PPE

goggles gloves lab_coat

Materials

  • Copper wire (20 gauge) (15 cm)
    Make a small loop at one end
  • Chloroform (CHCl₃) (2 mL)
    Positive control
  • Ethanol (C₂H₅OH) (2 mL)
    Negative control
  • Unknown organic samples (2 mL each)
    3–4 samples
  • Cork or holder for copper wire (1)

Equipment

Bunsen burner Watch glasses (6) Forceps

Procedure

1

Heat the copper wire loop in the oxidizing zone of the Bunsen burner until it glows red and no green color is visible (this burns off contaminants and forms CuO).

3 min Wire is extremely hot
2

Allow the wire to cool slightly, then dip it into the chloroform (positive control). Return the wire to the flame.

3 min Chloroform is volatile — use fume hood
3

Observe the bright green flame (positive result for halogen). Record the color and intensity.

2 min
4

Clean the wire by heating until green color disappears. Repeat the test with ethanol (negative control). No green color should appear.

3 min
5

Test each unknown sample using the same procedure. Record whether each gives a positive (green) or negative result.

10 min Clean wire between samples
6

Record all results and identify which unknowns likely contain halogen atoms.

4 min

Expected Results

Chloroform produces a vivid green flame (positive). Ethanol produces no green color (negative). Halogen-containing unknowns show green coloration of varying intensity.

Cleanup

Allow copper wire to cool. Store organic waste in halogenated or non-halogenated solvent waste containers as appropriate. Wipe down surfaces.

Details

Category
Qualitative Analysis
Difficulty
Beginner (Middle School)
Duration
25 min
Est. Cost
$5.00
Steps
6
Materials
5

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Frequently Asked Questions

What is the objective of Beilstein Test for Halogens?
Determine whether an organic compound contains halogen atoms (Cl, Br, I) using the Beilstein copper wire test.
How difficult is Beilstein Test for Halogens?
This experiment is rated as Beginner (Middle School). It takes approximately 25 minutes to complete.
What safety precautions are needed for Beilstein Test for Halogens?
Key safety precautions include: Chloroform is toxic — avoid inhalation and skin contact; Work in a fume hood when testing volatile organics; Hot copper wire can cause burns.
What materials are needed for Beilstein Test for Halogens?
The main materials required are: Copper wire (20 gauge), Chloroform (CHCl₃), Ethanol (C₂H₅OH), Unknown organic samples, Cork or holder for copper wire.
What results should I expect from Beilstein Test for Halogens?
Chloroform produces a vivid green flame (positive). Ethanol produces no green color (negative). Halogen-containing unknowns show green coloration of varying intensity.