卤素的贝尔斯坦测试

用铜丝焰色测试检测有机化合物中的卤素原子

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

目标

用贝尔斯坦铜丝测试判断有机化合物是否含有卤素原子（Cl、Br、I）。

背景

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).

安全警告

  • 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

所需PPE

goggles gloves lab_coat

材料

  • 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)

设备

Bunsen burner Watch glasses (6) Forceps

步骤

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 分钟 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 分钟 Chloroform is volatile — use fume hood
3

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

2 分钟
4

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

3 分钟
5

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

10 分钟 Clean wire between samples
6

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

4 分钟

预期结果

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

清理

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

详情

类别
Qualitative Analysis
难度
Beginner (Middle School)
时长
25 分钟
预估费用
$5.00
步骤数
6
材料
5

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Frequently Asked Questions

What is the objective of 卤素的贝尔斯坦测试?
用贝尔斯坦铜丝测试判断有机化合物是否含有卤素原子（Cl、Br、I）。
How difficult is 卤素的贝尔斯坦测试?
This experiment is rated as Beginner (Middle School). It takes approximately 25 minutes to complete.
What safety precautions are needed for 卤素的贝尔斯坦测试?
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 卤素的贝尔斯坦测试?
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 卤素的贝尔斯坦测试?
Chloroform produces a vivid green flame (positive). Ethanol produces no green color (negative). Halogen-containing unknowns show green coloration of varying intensity.