阿司匹林（乙酰水杨酸）的合成

制备世界上最常用的药物之一

Organic Synthesis Advanced (University) 90 分钟 ~$15.00

目标

通过乙酸酐对水杨酸的酰化反应合成阿司匹林（乙酰水杨酸），并通过熔点测定评估纯度。

背景

Aspirin synthesis is a classic organic chemistry experiment. Salicylic acid reacts with acetic anhydride in the presence of a phosphoric acid catalyst to form acetylsalicylic acid and acetic acid. The product is purified by recrystallization and verified by melting point (135°C for pure aspirin).

安全警告

  • Acetic anhydride is corrosive and has a pungent odor — work in fume hood
  • Phosphoric acid is corrosive
  • Do not consume the synthesized aspirin
  • Wear gloves and goggles

所需PPE

goggles gloves lab_coat

材料

  • Salicylic acid (2 g)
  • Acetic anhydride (5 mL)
    Corrosive, pungent
  • Phosphoric acid (H₃PO₄) (5 drops)
    85%, catalyst
  • Distilled water (100 mL)
    Ice-cold for crystallization
  • Ethanol (10 mL)
    For recrystallization

设备

Erlenmeyer flask (125 mL) Hot water bath (beaker) Buchner funnel Filter flask Vacuum pump Melting point apparatus Thermometer Ice bath

步骤

1

Weigh 2.0 g of salicylic acid into the Erlenmeyer flask. Record the exact mass.

3 分钟
2

In a fume hood, add 5 mL of acetic anhydride and 5 drops of phosphoric acid catalyst.

3 分钟 Acetic anhydride is corrosive and pungent
3

Heat the flask in a water bath at 70-80°C for 15 minutes, swirling occasionally.

15 分钟
4

Remove from heat and carefully add 20 mL of cold water to decompose excess acetic anhydride.

3 分钟 Exothermic — add water slowly
5

Cool the flask in an ice bath until crystals form. Scratch the flask wall with a glass rod to initiate crystallization.

10 分钟
6

Collect the crude product by vacuum filtration using the Buchner funnel. Wash with cold water.

10 分钟
7

Recrystallize: dissolve the crude product in 5 mL warm ethanol, add 15 mL warm water, then cool slowly in ice bath.

15 分钟
8

Collect purified crystals by vacuum filtration. Dry and determine the melting point.

10 分钟
9

Calculate the percent yield. Pure aspirin melts at 135°C.

5 分钟

预期结果

White needle-like crystals with a melting point of 134-136°C (pure aspirin is 135°C). Typical yield is 70-90%. A depressed or broad melting range indicates impurities (likely unreacted salicylic acid).

清理

Dispose of organic waste in designated containers. Do not consume the product. Rinse all glassware.

详情

类别
Organic Synthesis
难度
Advanced (University)
时长
90 分钟
预估费用
$15.00
步骤数
9
材料
5

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Frequently Asked Questions

What is the objective of 阿司匹林（乙酰水杨酸）的合成?
通过乙酸酐对水杨酸的酰化反应合成阿司匹林（乙酰水杨酸），并通过熔点测定评估纯度。
How difficult is 阿司匹林（乙酰水杨酸）的合成?
This experiment is rated as Advanced (University). It takes approximately 90 minutes to complete.
What safety precautions are needed for 阿司匹林（乙酰水杨酸）的合成?
Key safety precautions include: Acetic anhydride is corrosive and has a pungent odor — work in fume hood; Phosphoric acid is corrosive; Do not consume the synthesized aspirin.
What materials are needed for 阿司匹林（乙酰水杨酸）的合成?
The main materials required are: Salicylic acid, Acetic anhydride, Phosphoric acid (H₃PO₄), Distilled water, Ethanol.
What results should I expect from 阿司匹林（乙酰水杨酸）的合成?
White needle-like crystals with a melting point of 134-136°C (pure aspirin is 135°C). Typical yield is 70-90%. A depressed or broad melting range indicates impurities (likely unreacted salicylic acid).