📚 Esters for Edexcel IGCSE Chemistry | Edexcel IGCSE 化学：酯 考点精讲
Esters are an important family of organic compounds widely found in nature and used in everyday products. In IGCSE Edexcel Chemistry, you need to understand how esters form, name them, describe their properties and know their uses. This revision guide covers all essential concepts you must master for the exam.
酯是一类重要的有机化合物，广泛存在于自然界和日常用品中。在 IGCSE Edexcel 化学课程中，你需要了解酯的形成方式、命名方法、性质以及它们的用途。本复习指南涵盖考试必须掌握的所有核心概念。
1. What Are Esters? | 什么是酯？
Esters are organic compounds formed when a carboxylic acid reacts with an alcohol. They have the general formula R–COO–R', where R and R' are alkyl groups (such as —CH₃ or —C₂H₅). Esters are well known for their pleasant, fruity smells and are responsible for the aromas of many fruits.
酯是由羧酸和醇反应生成的有机化合物。它们的通式为 R–COO–R'，其中 R 和 R' 是烷基（如 —CH₃ 或 —C₂H₅）。酯以其令人愉悦的水果香味而闻名，是许多水果香气的来源。
Unlike carboxylic acids, esters are neutral compounds and do not ionise to release H⁺ ions. They are covalent molecules with relatively low boiling points compared to acids of similar molecular mass.
与羧酸不同，酯是中性化合物，不会电离出 H⁺ 离子。它们是共价分子，与相对分子质量相近的羧酸相比沸点较低。
2. The Ester Functional Group | 酯的官能团
The functional group of an ester is –COO– ) attached to an oxygen atom that is also bonded to another carbon chain. This linking group gives esters their characteristic chemical behaviour.
酯的官能团是 –COO–。它由一个羰基（C=O）和一个氧原子连接而成，该氧原子又与另一个碳链键合。这一连接基团赋予了酯独特的化学性质。
unctional group in structural formulas. In a displayed formula, the ester group appears as —C(=O)—O—. Do not confuse it with the carboxyl group —COOH.
在结构式中识别该官能团至关重要。在展示式中，酯基表现为 —C(=O)—O—。不要将其与羧基 —COOH 混淆。
3. Esterification Reaction | 酯化反应
The formation of an ester from a carboxylic acid and an alcohol is called esterification (or condensation). It is a reversible reaction, represented by:
由羧酸和醇生成酯的反应称为酯化反应（或缩合反应）。这是一个可逆反应，可用下式表示：
Carboxylic acid + Alcohol ⇌ Ester + Water
For example, ethanoic acid reacts with ethanol to form ethyl ethanoate and water:
例如，乙酸与乙醇反应生成乙酸乙酯和水：
CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O
In this condensation reaction, a small molecule (water) is eliminated as the ester bond forms. The reaction is slow at room temperature and requires heating under reflux with a catalyst.
在此缩合反应中，一个小分子（水）被脱除，同时形成酯键。室温下反应很慢，需要加热回流并使用催化剂。
4. Conditions for Esterification | 酯化反应的条件
The esterification reaction is catalysed by a strong acid, typically concentrated sulfuric acid (H₂SO₄). This acid
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