IGCSE CIE Chemistry: Alkenes Exam Tips | IGCSE CIE 化学：烯烃 考点精讲

📚 IGCSE CIE Chemistry: Alkenes Exam Tips | IGCSE CIE 化学：烯烃 考点精讲

Alkenes are a fundamental homologous series of unsaturated hydrocarbons containing at least one carbon-carbon double bond (C=C). In the Cambridge IGCSE Chemistry syllabus, you need to understand their structure, naming, addition reactions, and polymerisation. This article summarises the key exam points to help you ace your test.

烯烃是一类重要的不饱和碳氢化合物同系列，分子中含有至少一个碳碳双键（C=C）。在剑桥 IGCSE 化学大纲中，你需要掌握其结构、命名、加成反应和聚合反应。本文总结关键考点，助你考试夺优。

1. Introduction to Alkenes | 烯烃简介

Alkenes are unsaturated hydrocarbons that contain at least one C=C double bond. They belong to the same homologous series, with each member differing by a CH₂ unit. The simplest alkene is ethene (C₂H₄).

烯烃是不饱和烃，含有至少一个 C=C 双键。它们属于同一类同系列，每相邻成员相差一个 CH₂ 单元。最简单的烯烃是乙烯 (C₂H₄)。

Because of the double bond, alkenes are more reactive than alkanes and undergo addition reactions, making them highly useful as chemical feedstocks.

由于双键的存在，烯烃比烷烃更活泼，可发生加成反应，因此是极具价值的化工原料。

2. General Formula and Functional Group | 通式与官能团

Alkenes have the general formula CₙH₂ₙ. Their functional group is the carbon-carbon double bond, >C=C<, which is responsible for their characteristic reactions.

烯烃的通式为 CₙH₂ₙ。其官能团是碳碳双键 >C=C<，决定了它们的特征反应。

For example, ethene is C₂H₄ and propene is C₃H₆. Note that for every carbon atom in the chain, there are twice as many hydrogen atoms, giving a relatively high carbon-to-hydrogen ratio.

例如，乙烯为 C₂H₄，丙烯为 C₃H₆。注意链中每有一个碳原子，氢原子数为其两倍，因此碳氢比较高。

3. Naming Alkenes | 烯烃的命名

IUPAC naming of alkenes follows these rules: select the longest carbon chain containing the double bond; number the chain so that the double bond gets the lowest possible number; use the suffix -ene. Indicate the position of the double bond by a number before the name.

烯烃的 IUPAC 命名规则：选取包含双键的最长碳链；

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