裂解

物料与用量

• Liquid paraffin — five or six drops on mineral wool; about 0.5 cm of the tube occupied
• Aluminium oxide — one microspatula
• Bromine water, 0.01 mol dm⁻³ — half-fill the receiving well; about 3 cm³ available per group
• Mineral wool — a small plug
• Ethanol or industrial denatured alcohol — microburner fuel

仪器装置

• Two microscale well plates with ported lids
• 10 cm³ gas syringe
• Straight narrow-bore glass tube and two L-shaped glass tubes
• Short lengths of silicone tubing
• Dropping pipette
• Ethanol microburner
• Eye protection

实验步骤

1. Connect the gas syringe to the inlet well and half-fill the receiving well with bromine water before joining the two wells through the glass reaction tube.
2. Place mineral wool two to three centimetres into the inlet end of the straight tube, add five or six drops of liquid paraffin, and place one microspatula of aluminium oxide at the opposite end.
3. Assemble the tube horizontally with the paraffin nearest the gas-syringe end and the catalyst nearest the bromine-water end.
4. Heat the aluminium oxide strongly first while depressing the syringe very slowly, then flick the heat over the paraffin so its vapour passes across the hot catalyst.
5. Continue the slow gas flow until the bromine-water colour no longer changes or the paraffin is exhausted, then stop heating and allow all glassware to cool before dismantling.

关键控制条件

• Wear eye protection throughout setup, heating and dismantling; the narrow glass tubes can break while tubing is fitted.
• Keep the ethanol microburner upright and closed except as instructed; its vapour is highly flammable.
• Maintain a slow positive gas flow to reduce suck-back of bromine water into the hot tube.
• The product mixture shows unsaturation by bromine-water decolourisation.