酯类
Edexcel 国际普通中等教育证书（IGCSE）化学· 4.38C–4.43C· 18 分钟阅读
1. 酯的结构与官能团★★☆☆☆HL 专属⏱ 3 min
酯键
定义所有酯类的共价官能团，由羧酸与醇反应生成
例:
In ethyl ethanoate, the ester linkage connects the ethyl group from ethanol to the ethanoate group from ethanoic acid
所有酯都符合通式RCOOR'，其中R是来自母体羧酸的烷基（或氢原子），R'是来自母体醇的烷基。展开式必须明确显示所有化学键，包括酯键中的C=O双键与C-O单键。
画出酯官能团的展开式，标出用于连接烷基的未成键位点。
- 1
画出中心碳原子，与一个氧原子形成双键
- 2
从同一个碳原子出发，以单键连接第二个氧原子
- 3
标出两个未成键位点：一个在中心碳原子上（连接来自酸的烷基），另一个在单键连接的氧原子上（连接来自醇的烷基）
Which functional group is present in all esters?
A -OH
B -COOH
C -COO-
D -C=C-
显示答案
C —A is the alcohol functional group, B is the carboxylic acid functional group, D is the alkene functional group.
2. 酯的命名与分子式书写★★★☆☆HL 专属⏱ 5 min
无论母体反应物的大小如何，酯的命名都遵循固定的两部分规则。考试要求你能够从给定反应物推导酯的名称，也能从给定酯的名称识别对应的母体反应物。
写出甲醇与丙酸反应生成的酯的名称，并写出其结构式。
- 1
从母体醇中提取烷基：甲醇 → 甲基
- 2
将母体羧酸的-oic acid后缀替换为-oate：丙酸 → 丙酸酯
- 3
将两部分组合得到酯的名称：丙酸甲酯
- 4
写出结构式：CH₃CH₂COOCH₃
确定生成乙酸丁酯所使用的母体醇与羧酸。
- 1
酯名称的第一部分（丁基）来自醇：丁醇
- 2
酯名称的第二部分（乙酸酯基）来自羧酸：乙酸
Exam tip:
酯的命名顺序与反应物顺序相反：来自醇的基团放在前面，后面接来自酸的-oate（酸酯）后缀。
3. 乙酸乙酯的生成★★★☆☆HL 专属⏱ 4 min
乙酸乙酯是考试中最常考察的酯类，由乙醇与乙酸在浓硫酸催化下发生可逆缩合反应生成，反应同时生成一分子水作为副产物。
写出乙酸乙酯生成反应的完整配平符号方程式，注明催化剂。
- 1
写出反应物的分子式：乙酸（CH₃COOH）和乙醇（C₂H₅OH）
- 2
写出产物的化学式：乙酸乙酯（CH₃COOC₂H₅）和水（H₂O）
- 3
验证原子守恒：方程式两侧均含有4个C原子、10个H原子和3个O原子
- 4
在反应箭头上方标注浓H₂SO₄以表示催化剂
4. 酯的性质与用途★★☆☆☆HL 专属⏱ 2 min
酯具有两项核心物理性质，这两项性质决定了它们的商业用途：它们挥发性极强（室温下极易蒸发），且带有独特的香甜水果气味。
Food flavourings: Used to replicate the taste and smell of fruits like strawberry, banana, and pineapple in processed foods, confectionery and drinks
Perfumes: Their volatility means fragrant ester molecules travel easily through air to reach the nose, making them ideal for scented products
解释为什么酯可用于香水生产。
- 1
酯带有独特宜人的水果香气，正是香水产品所需要的气味
- 2
酯具有挥发性，因此带香气的分子极易蒸发，使用者和周边的人都能闻到气味
5. 乙酸乙酯的实验室制备实操★★★★☆HL 专属⏱ 4 min
🚫 计算器禁用
你需要熟记中学实验室制备少量乙酸乙酯的简易方法，包括核心的安全注意事项。
Add equal volumes of ethanol and ethanoic acid to a boiling tube
Add 3-4 drops of concentrated sulfuric acid catalyst to the mixture
Warm the tube gently in a 60°C hot water bath for 5 minutes (avoid open flames, as ethanol is flammable)
Pour the resulting mixture into a beaker of cold sodium carbonate solution to neutralise unreacted acid and remove impurities
An insoluble, sweet-smelling oily layer of ethyl ethanoate will form on the surface of the solution
写出该实验的一项安全注意事项，并说明其必要性。
- 1
使用热水浴加热，禁止直接用本生灯明火加热
- 2
乙醇属于高度易燃物，明火可能引燃反应混合物
6. 常见陷阱
错误做法:
Naming esters in the same order as reactants (e.g. ethanol + ethanoic acid → ethanoic ethyl ester)
原因:
Ester names reverse the order of parent reactants, with the alcohol-derived group first.
正确做法:
Name the alcohol alkyl group first, followed by the acid-derived -oate suffix.
错误做法:
Drawing the ester linkage with incorrect bonding, e.g. -CO-OH or -O-CO- with missing double bond
原因:
The ester functional group is explicitly -COO- with a C=O double bond adjacent to a C-O single bond.
正确做法:
Show all bonds in displayed formulae, including the C=O double bond in the ester linkage.
错误做法:
Omitting water as a product in esterification balanced equations
原因:
Esterification is a condensation reaction that eliminates one molecule of water per ester molecule formed.
正确做法:
Always include H₂O as a product when writing esterification equations.
错误做法:
Stating dilute sulfuric acid is used as the esterification catalyst
原因:
Only concentrated sulfuric acid acts as an effective catalyst, and also absorbs water to shift equilibrium towards ester products.
正确做法:
Explicitly state 'concentrated sulfuric acid' when naming the catalyst.
错误做法:
Confusing ester uses with carboxylic acid uses (e.g. stating esters are used as cleaning agents)
原因:
Esters have sweet smells and volatility, while carboxylic acids have acidic cleaning properties.
正确做法:
Only recall the two specified uses: food flavourings and perfumes.
7. 速查表
Concept | Key Exam Fact |
|---|---|
Ester functional group | -COO- (ester linkage) |
Ester naming rule | Alkyl (alcohol) + -oate (carboxylic acid) |
Ethyl ethanoate reactants | Ethanol + ethanoic acid |
Esterification catalyst | Concentrated sulfuric acid |
Key ester properties | Volatile, sweet/fruity smell |
Ester uses | Food flavourings, perfumes |
Practical test for ester | Sweet oily layer on sodium carbonate solution |
8. 常见问题
我需要明确写出酯化反应的特定催化剂吗？
是的，你必须明确写出浓硫酸才能拿到全分，不能只笼统写“酸催化剂”。
4CH1考纲包含酯的水解内容吗？
不包含，该子主题仅要求掌握酯的生成、性质、用途与命名。
酯的命名各部分的顺序是什么？
名称的第一部分来自母体醇（烷基），第二部分来自母体羧酸，后缀使用-oate（酸酯）。
深入阅读
下一步
Now you have mastered ester content for Edexcel IGCSE 4CH1 Paper 2C, you are ready to progress to related organic chemistry sub-topics. Esters are a core building block for understanding condensation polymerisation, where ester linkages connect monomer units to form polyesters, a common synthetic material. You should also consolidate your knowledge of alcohols and carboxylic acids, as exam questions frequently combine content from these three sub-topics in longer structured responses. Be sure to practice writing displayed formulae for esters and balanced esterification equations, as these are common high-mark questions on Paper 2C.