Test de Beilstein pour les Halogènes

Détection des atomes d'halogène dans les composés organiques par le test de flamme au fil de cuivre

Qualitative Analysis Beginner (Middle School) 25 min ~$5,00

Objectif

Déterminer si un composé organique contient des atomes d'halogène (Cl, Br, I) à l'aide du test de Beilstein au fil de cuivre.

Contexte

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).

Avertissements de sécurité

  • 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

EPI requis

goggles gloves lab_coat

Matériaux

  • 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)

Équipement

Bunsen burner Watch glasses (6) Forceps

Procédure

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

Résultats attendus

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

Nettoyage

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

Détails

Catégorie
Qualitative Analysis
Difficulté
Beginner (Middle School)
Durée
25 min
Coût estimé
$5,00
Étapes
6
Matériaux
5

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Frequently Asked Questions

What is the objective of Test de Beilstein pour les Halogènes?
Déterminer si un composé organique contient des atomes d'halogène (Cl, Br, I) à l'aide du test de Beilstein au fil de cuivre.
How difficult is Test de Beilstein pour les Halogènes?
This experiment is rated as Beginner (Middle School). It takes approximately 25 minutes to complete.
What safety precautions are needed for Test de Beilstein pour les Halogènes?
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 Test de Beilstein pour les Halogènes?
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 Test de Beilstein pour les Halogènes?
Chloroform produces a vivid green flame (positive). Ethanol produces no green color (negative). Halogen-containing unknowns show green coloration of varying intensity.