Carboxylic Acids and Their Derivatives | 羧酸及其衍生物

📚 Carboxylic Acids and Their Derivatives | 羧酸及其衍生物

Carboxylic acids are a homologous series containing the carboxyl functional group, -COOH. Their derivatives, including acyl chlorides, acid anhydrides, esters and amides, share the acyl group RCO- but differ in the group attached to the carbonyl carbon. These compounds are central to organic synthesis, biological chemistry and industrial polymer production.

羧酸是含有羧基官能团 -COOH 的同系物。它们的衍生物包括酰氯、酸酐、酯和酰胺，都含有共同的酰基 RCO-，但羰基碳上连接的基团不同。这些化合物在有机合成、生物化学和工业聚合物生产中处于核心地位。

1. Structure and Nomenclature | 结构与命名

The carboxyl group consists of a carbonyl group (C=O) bonded directly to a hydroxyl group (-OH). The carbon atom is sp² hybridised, so the functional group is planar and the C=O and C-O bonds show partial double-bond character due to electron delocalisation.

羧基由直接与羟基 (-OH) 相连的羰基 (C=O) 组成。该碳原子为 sp² 杂化，因此官能团为平面结构；由于电子离域，C=O 和 C-O 键都具有一定的双键性质。

In IUPAC nomenclature, the longest chain containing the -COOH group is selected and the suffix -oic acid is used. The carboxyl carbon is always position 1, so no locant is needed, e.g. methanoic acid HCOOH and ethanoic acid CH₃COOH.

在 IUPAC 命名中，选择含 -COOH 的最长碳链，后缀使用 -oic acid（中文为酸）。羧基碳总是编号为 1，因此无需标明位置，例如甲酸 HCOOH 和乙酸 CH₃COOH。

Dicarboxylic acids such as ethanedioic acid HOOC-COOH and propanedioic acid HOOC-CH₂-COOH contain two carboxyl groups and are named with -dioic acid.

二元羧酸如乙二酸 HOOC-COOH 和丙二酸 HOOC-CH₂-COOH 含有两个羧基，命名时使用 -dioic acid（中文为二酸）。

2. Physical Properties and Solubility | 物理性质与溶解性

Carboxylic acids have unusually high boiling points for their molecular mass because two acid molecules can form a hydrogen-bonded dimer. This dimer involves two O-H···O interactions between the carbonyl oxygen of one molecule and the hydroxyl hydrogen of another.

羧酸的沸点相对其分子质量异常高，因为两个酸分子可以通过氢键形成二聚体。该二聚体包含一个分子的羰基氧与另一个分子的羟基氢之间的两个 O-H···O 相互作用。

Short-chain carboxylic acids such as methanoic and ethanoic acid are fully miscible with water

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