Mastering Edexcel A-Level Chemistry Topic 17: Organic Chemistry II | 掌握爱德思 A-Level 化学专题 17：有机化学 II

📚 Mastering Edexcel A-Level Chemistry Topic 17: Organic Chemistry II | 掌握爱德思 A-Level 化学专题 17：有机化学 II

Welcome to this TutorHao revision guide for Edexcel A-Level Chemistry Topic 17: Organic Chemistry II. This topic develops the chemistry of carbonyl compounds, carboxylic acids, esters, acyl chlorides, amines, amides, amino acids and organic synthesis. It builds directly on Topic 6 and provides essential techniques for answering longer synthesis and mechanism questions.

欢迎阅读 TutorHao 为爱德思 A-Level 化学专题 17：有机化学 II 编写的复习讲义。本专题深入讲解羰基化合物、羧酸、酯、酰氯、胺、酰胺、氨基酸及有机合成，并在专题 6 的基础上拓展，是应对合成路线与机理长题的关键内容。

1. Overview: Functional Groups in Topic 17 | 概述：专题 17 的官能团

Topic 17 centres on oxygen- and nitrogen-containing organic families: aldehydes, ketones, carboxylic acids, esters, acyl chlorides, amides, amines and amino acids. You must be able to recognise their functional groups, apply IUPAC naming and link reagents to transformations.

专题 17 以含氧和含氮有机物家族为核心：醛、酮、羧酸、酯、酰氯、酰胺、胺和氨基酸。你必须能够识别它们的官能团、运用 IUPAC 命名法并将试剂与转化联系起来。

• Carbonyl group C=O: present in aldehydes and ketones | 羰基 C=O：存在于醛和酮中
• Carboxyl group COOH: present in carboxylic acids | 羧基 COOH：存在于羧酸中
• Ester link COO: present in esters | 酯键 COO：存在于酯中
• Acyl chloride group COCl: present in acyl chlorides | 酰氯基 COCl：存在于酰氯中
• Amine group NH₂: present in primary amines | 氨基 NH₂：存在于伯胺中
• Amide link CONH: present in amides | 酰胺键 CONH：存在于酰胺中

2. Aldehydes and Ketones: Structure and Naming | 醛和酮：结构与命名

Aldehydes have the carbonyl group at the end of a carbon chain, with at least one hydrogen attached, while ketones have the carbonyl group between two carbon atoms. The aldehyde functional group is written as CHO and the ketone group as CO.

醛的羰基位于碳链末端，并且至少连接一个氢原子；酮的羰基则位于两个碳原子之间。醛的官能团写作 CHO，酮的官能团写作 CO。

IUPAC naming uses the suffix -al for aldehydes and -one for ketones. For example, ethanal is CH₃CHO and propanone is CH₃COCH₃.

IUPAC 命名中醛以 -al 结尾，酮以 -one 结尾。例如乙醛是 CH₃CHO，丙酮是 CH₃COCH₃。

Because the carbonyl carbon is trigonal planar and polarised, aldehydes and ketones undergo nucleophilic addition rather than substitution. The δ+ carbon is attacked by nucleophiles such as H⁻ from NaBH₄ or CN⁻ from HCN.

由于羰基碳为平面三角形且具有极性，醛和酮发生亲核加成而非取代反应。带 δ+ 的碳会受到 NaBH₄ 中的 H⁻ 或 HCN 中的 CN⁻ 等亲核试剂的进攻。

Aldehydes and ketones are polar molecules, so they have higher boiling points than alkanes of similar molar mass. However, they cannot form hydrogen bonds with themselves because there is no hydrogen attached to oxygen, so their boiling points are lower than alcohols.

醛和酮是极性分子，因此其沸点高于摩尔质量相近的烷烃。但由于氧上没有连接氢，它们自身不能形成氢键，所以沸点低于相应醇。

3. Nucleophilic Addition Mechanism | 亲核加成机理

The nucleophilic addition mechanism for ethanal with HCN can be shown in three steps: the cyanide ion attacks the δ+ carbon, the C=O bond breaks, and the oxygen gains a hydrogen ion from HCN or water to form 2-hydroxypropanenitrile.

乙醛与 HCN 的亲核加成机理可分三步：氰根离子进攻 δ+ 碳，C=O 键断裂，氧从 HCN 或水中获得氢离子生成 2-羟基丙腈。

CH₃CHO + HCN → CH₃CH(OH)CN

Use curly arrows carefully: the first arrow goes from the lone pair on CN⁻ to the carbonyl carbon; the second arrow goes from the C=O bond to the oxygen atom.

使用弯箭头时要准确：第一个箭头从 CN⁻ 的孤对电子指向羰基碳；第二个箭头从 C=O 键指向氧原子。

In acidic or neutral HCN, the cyanide ion is generated in low concentration, so the reaction is slow unless a base catalyst is present. This is why KCN followed by dilute acid is often used in the laboratory.

在酸性或中性 HCN 中，氰根离子浓度很低，因此反应较慢，除非存在碱催化剂。所以实验室常使用 KCN 再以稀酸处理。

The same nucleophilic addition mechanism applies when NaBH₄ reduces a carbonyl compound. The hydride ion, H⁻, attacks the carbonyl carbon and then the intermediate alkoxide ion is protonated by water.

当 NaBH₄ 还原羰基化合物时，也遵循相同的亲核加成机理。氢负离子 H⁻ 进攻羰基碳，随后中间体烷氧负离子被水质子化。

4. Reduction and Oxidation Reactions | 还原与氧化反应

Sodium borohydride, NaBH₄, in water or methanol reduces aldehydes to primary alcohols and ketones to secondary alcohols. The hydride ion, H⁻, acts as the reducing agent and adds to the carbonyl carbon.

硼氢化钠 NaBH₄ 在水或甲醇中将醛还原为伯醇，将酮还原为仲醇。氢负离子 H⁻ 作为还原剂进攻羰基碳。

Oxidation of aldehydes can be achieved using acidified potassium dichromate(VI), H⁺/Cr₂O₇²⁻, under reflux. Aldehydes are oxidised to carboxylic acids, while ketones resist oxidation because breaking a C-C bond would be required.

醛可在回流条件下被酸化重铬酸钾 H⁺/Cr₂O₇²⁻ 氧化为羧酸；酮则难以被氧化，因为需要断裂 C-C 键。

RCHO + [O] → RCOOH

Fehling’s solution and Tollens’ reagent are used as tests for aldehydes. Fehling’s gives a brick-red precipitate of Cu₂O, and Tollens’ forms a silver mirror on the inside of a test tube.

费林试剂与托伦试剂可用于检验醛。费林试剂产生砖红色 Cu₂O 沉淀，托伦试剂在试管内壁形成银镜。

When using acidified dichromate to distinguish aldehydes from ketones, the colour changes from orange to green for aldehydes because Cr(VI) is reduced to Cr(III). Ket

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