卤素加成

物料与用量

• Potassium bromate(V), 0.1 mol dm⁻³ — 10 drops
• Potassium bromide, 0.2 mol dm⁻³ — 20 drops
• Hydrochloric acid, 1 mol dm⁻³ — five drops
• Hexane — enough to half-fill the preparation well
• Cyclohexene — three drops
• Prepared bromine-in-hexane solution — three drops

仪器装置

• 24-well plastic plate
• Standard plastic pipettes used as micro separating funnels
• Plastic Petri dish
• Eye protection

实验步骤

1. Combine ten drops of bromate solution, 20 drops of bromide solution and five drops of hydrochloric acid in one well; leave for five minutes for bromine formation.
2. Add hexane until the well is about half-full, draw the liquid into a plastic pipette, invert it and mix gently until bromine transfers into the upper hexane layer.
3. Separate the lower aqueous layer and place the bromine-containing hexane layer in a clean well.
4. Place three drops of bromine-in-hexane solution in a test well, add three drops of cyclohexene, and record the rapid loss of bromine colour.

后处理与分离

1. Do not isolate or handle the small-scale addition product in this diagnostic method.
2. Decontaminate remaining bromine solution using the disposal procedure specified by the source and local laboratory rules.

关键控制条件

• Use a well-ventilated laboratory, eye protection and suitable gloves; bromine and hexane are hazardous and hexane is highly flammable.
• Keep liquids contained in the plastic pipette during extraction and invert gently so solvent is not expelled.
• Bromine decolourisation detects unsaturation; product analysis is listed separately.