📚 Naming Organic Compounds | 有机化合物的命名
IUPAC nomenclature provides a systematic way to name organic molecules, ensuring that each compound has a unique and universally understood name. For A-Level Chemistry students, mastering these rules is essential for accurately identifying and communicating chemical structures.
IUPAC 命名法为有机分子提供了一套系统命名方式，确保每个化合物拥有唯一且通用的名称。对 A-Level 化学学生来说，掌握这些规则是准确识别和交流化学结构的关键。
1. Introduction to IUPAC Nomenclature | IUPAC命名法简介
The International Union of Pure and Applied Chemistry (IUPAC) developed a set of rules that link a name to a specific molecular structure. The core of an IUPAC name consists of a root (indicating the longest carbon chain), a suffix (showing the principal functional group), and prefixes (for substituents and lower-priority groups). Numbers (locants) are used to indicate the positions of multiple bonds and substituents.
国际纯粹与应用化学联合会（IUPAC）制定了一套将名称与特定分子结构联系起来的规则。IUPAC 名称的核心由母体（表示最长碳链）、后缀（指示主要官能团）和前缀（取代基及低优先级基团）构成，并使用数字（位次）标注重键和取代基的位置。
Understanding this basic framework allows chemists to interpret the name and deduce the structure, and vice versa. The system is hierarchical: the functional group with the highest priority determines the suffix, while others become prefixes.
理解这一基本框架后，化学家可以从名称推断结构，反之亦然。该系统分层次：优先级最高的官能团决定后缀，其余则作为前缀。
2. Naming Alkanes | 烷烃的命名
Alkanes are saturated hydrocarbons with the general formula CₙH₂ₙ₊₂. Their names end in '-ane'. The longest continuous carbon chain provides the stem (e.g., meth- for 1, eth- for 2, prop- for 3, but- for 4, pent- for 5, hex- for 6, hept- for 7, oct- for 8, non- for 9, dec- for 10).
烷烃是通式为 CₙH₂ₙ₊₂ 的饱和烃，名称以“-ane”结尾。最长的连续碳链提供词干（如 meth- 表示 1、eth- 表示 2、prop- 表示 3、but- 表示 4、pent- 表示 5、hex- 表示 6、hept- 表示 7、oct- 表示 8、non- 表示 9、dec- 表示 10）。
If there are branched substituents (alkyl groups), identify and name them (methyl, ethyl, propyl, etc.). Number the chain from the end that gives the substituent the lowest possible locant. When two or more identical substituents are present, use multiplying prefixes (di-, tri-, tetra-) and list locants separated by commas. The substituents are arranged alphabetically (ignoring multipliers) before the parent name.
若有支链取代基（烷基），需识别并命名它们（甲基、乙基、丙基等）。从能使取代基获得最小编号的一端给碳链编号。当存在两个或多个相同取代基时，使用倍乘前缀（二、三、四），并用逗号分隔位次。取代基按字母顺序排列（忽略倍乘前缀）置于母体名称前。
For example, 2,3-dimethylpentane has a five-carbon parent chain with methyl groups on carbons 2 and 3.
例如，2,3-二甲基戊烷的母链为五个碳，在 2 和 3 号碳上有甲基。
3. Naming Alkenes and Alkynes | 烯烃和炔烃的命名
Alkenes contain a carbon-carbon double bond (C=C) and use the suffix '-ene'; alkynes have a triple bond (C≡C) and end in '-yne' uble or triple bond is placed immediately before the suffix (e.g., but-2-ene, pent-1-yne).
烯烃含有碳碳双键 (C=C)，使用后缀“-ene”；炔烃含有三键 (C≡C)，以“-yne”结尾。主链必须包含重键，且编号应使重键获得最小编号。双键或三键的位次紧邻后缀放置（如 but-2-ene、pent-1-yne）。
When the molecule contains both a double bond and a triple bond, the suffix becomes '-enyne', with the double bond given the lower number if possible. When numbering, the double bond takes priority over the triple bond only if there is no choice that gives both lowest numbers; otherwise, number to give the set of locants the lowest sum.
当分子中同时存在双键和三键时，后缀变为“-enyne”，并尽可能使双键编号更小。编号时，只有在无法使两类键都获得最小位次时，双键才优先于三键；否则应使位次总和尽可能小。
4. Naming Cyclic Hydrocarbons | 环烃的命名
Cycloalkanes, cycloalkenes, and cycloalkynes are named by adding the prefix 'cyclo-' to the corresponding open-chain name. For instance, a six-membered saturated ring is cyclohexane. Numbering begins at one point of the ring and proceeds to give substituents the lowest possible numbers. If there is only one substituent, no locant is needed.
环烷烃、环烯烃和环炔烃的命名是在相应开链名称前加上前缀“cyclo-”。例如，六元饱和环为环己烷。编号从环上某一点开始，使取代基获得尽可能小的位次。若只有一个取代基，则无需标位次。
When a ring contains a double or triple bond, the multiple bond is always given locants 1 and 2, and numbering continues to give substituents the lowest numbers. If a functional group with higher priority is present, the ring may become a substituent with the name ending in '-yl' (e.g., cyclohexyl).
当环含有双键或三键时，重键始终占据位次 1 和 2，然后继续编号使取代基位次最小。若存在更高优先级的官能团，环可作为取代基，名称以“-yl”结尾（如 cyclohexyl）。
5. Functional Group Priority | 官能团优先级
The principal functional group determines the suffix of the name, according to a strict priority order. The highest-priority group within a molecule must be expressed as the suffix, while all others become prefixes. The following table summarises the priority commonly tested at A-Level:
主要官能团按照严格的优先次序决定名称的后缀。分子中优先级最高的基团必须以后缀形式出现，其余则作为前缀。下表总结 A-Level 常考优先级：
| Priority | Functional Group | Suffix | Prefix |
|---|---|---|---|
| Highest | Carboxylic acid -COOH | -oic acid | carboxy- |
| Ester -COOR | -oate | alkoxycarbonyl- | |
| Amide -CONH₂ | -amide | carbamoyl- | |
| Nitrile -CN | -nitrile | cyano- | |
| Aldehyde -CHO | -al | formyl- | |
| Ketone >C=O | -one | oxo- | |
| Alcohol -OH | -ol | hydroxy- | |
| Amine -NH₂ | -amine | amino- | |
| Alkene >C=C< | -ene | - | |
| Lowest | Halogen -X | - | fluoro-, chloro-, bromo-, iodo- |
Note that the carboxyl group always receives the lowest locant unless a higher priority group is present. When constructing a name, the suffix is derived from the highest-priority group, and all other groups become prefixes in alphabetical order.
注意，除非存在更高优先级基团，羧基始终获得最小编号。构建名称时，后缀来自优先级最高的基团，其他所有基团按字母顺序变为前缀。
6. Naming Haloalkanes | 卤代烷的命名
Halogen substituents (F, Cl, Br, I) are treated as prefixes: fluoro-, chloro-, bromo-, and iodo-. The parent chain is numbered to give the lowest possible set of numbers to the halogen(s). If a choice exists, the carbon bearing the halogen with higher atomic mass takes precedence. Like alkyl groups, halogens are listed alphabetically when multiple different halogens are present.
卤素取代基（F、Cl、Br、I）作为前缀使用：fluoro-、chloro-、bromo-、iodo-。母链编号应使卤素获得尽可能低的位次集合。若有选择，原子质量更大的卤素优先。当存在多种不同卤素时，按字母顺序排列。
For example, 2-bromo-1-chloropropane indicates a three-carbon chain with bromine on C2 and chlorine on C1. Note that 'bromo' comes before 'chloro' alphabetically.
例如，2-bromo-1-chloropropane 表示一条三碳链，溴在 C2，氯在 C1。注意字母顺序中“bromo”在“chloro”之前。
7. Naming Alcohols and Ethers | 醇和醚的命名
Alcohols contain the hydroxyl group -OH. The suffix is '-ol', and the parent chain must include the carbon attached to the OH group. Number the chain to give the carbon with the OH group the lowest possible locant, placed immediately before the suffix (e.g., propan-2-ol). If higher-priority groups are present, OH becomes the prefix 'hydroxy-'.
醇含有羟基 -OH。后缀为“-ol”，母链必须包含连接 OH 的碳。编号应使带有 OH 的碳获得最小编号，该位次紧邻后缀之前（如 propan-2-ol）。若存在更高优先级基团，OH 作为前缀“hydroxy-”。
Ethers have the functional group -O- linking two carbon chains. They are named by identifying the two alkyl groups (in alphabetical order) followed by the word 'ether' (e.g., ethyl methyl ether). In IUPAC, the larger chain becomes the parent name, and the smaller chain with the oxygen is treated as an alkoxy substituent (methoxy-, ethoxy-). E.g., methoxyethane.
醚具有连接两条碳链的官能团 -O-。其命名是识别两个烷基（按字母顺序）后加“ether”（如 ethyl methyl ether）。在 IUPAC 体系中，较长的链作母体，较短的链连同氧作为烷氧基取代基（如 methoxy-, ethoxy-），例如甲氧基乙烷（methoxyethane）。
8. Naming Aldehydes and Ketones | 醛和酮的命名
Aldehydes contain the carbonyl group at the end of a carbon chain: -CHO. The suffix is '-al', and the carbonyl carbon is always C1, so no locant is needed for the aldehyde group itself. The longest chain bearing the -CHO group is the parent. If the aldehyde is attached to a ring, the suffix '-carbaldehyde' is used.
醛含有位于碳链末端的羰基 -CHO。后缀为“-al”，羰基碳始终是 C1，因此醛基本身不需要位次。带有 -CHO 的最长碳链为母体。若醛基连接在环上，则使用后缀“-carbaldehyde”。
Ketones have a carbonyl group (C=O) bonded to two carbon atoms. The suffix is '-one' re the suffix (e.g., pentan-2-one). When the ketone is not the principal group, the prefix 'oxo-' is used, with a locant.
酮的羰基 (C=O) 与两个碳原子相连。后缀为“-one”，编号应使羰基碳获得最小编号，并置于后缀前（如 pentan-2-one）。若酮基不是主官能团，则使用前缀“oxo-”并标位次。
9. Naming Carboxylic Acids and Derivatives | 羧酸及其衍生物的命名
Carboxylic acids (-COOH) take the suffix '-oic acid'. The carbonyl carbon is always C1, so no locant is used for the carboxyl group. For diacids, the suffix is '-dioic acid'. If the -COOH group is attached to a ring, the name ends in '-carboxylic acid'.
羧酸 (-COOH) 使用后缀“-oic acid”。羰基碳始终为 C1，因此羧基无需位次。对于二元酸，后缀为“-dioic acid”。若 -COOH 连接在环上，则名称以“-carboxylic acid”结尾。
Esters are derived from carboxylic acids and alcohols. The alkyl group from the alcohol is named first, followed by the carboxylate part derived from the acid: the acid name changes from '-oic acid' to '-oate'. For example, ethyl ethanoate is formed from ethanol and ethanoic acid.
酯由羧酸和醇生成。先命名来自醇的烷基，再命名来自酸的羧酸根部分：酸名由“-oic acid”变为“-oate”。例如，乙酸乙酯 (ethyl ethanoate) 由乙醇和乙酸形成。
Acid chlorides change '-oic acid' to '-oyl chloride' (e.g., ethanoyl chloride), and acid anhydrides replace 'acid' with 'anhydride' (e.g., ethanoic anhydride). Amides replace '-oic acid' with '-amide' (e.g., ethanamide).
酰氯将“-oic acid”变为“-oyl chloride”（如 ethanoyl chloride），酸酐将“acid”改为“anhydride”（如 ethanoic anhydride）。酰胺则将“-oic acid”变为“-amide”（如 ethanamide）。
10. Naming Amines and Amides | 胺和酰胺的命名
Amines are derivatives of ammonia where one or more hydrogens are replaced by alkyl or aryl groups. Primary amines are named by adding the suffix '-amine' to the alkyl group name (e.g., ethylamine, C₂H₅NH₂). When the amine is not the principal group, the prefix 'amino-' is used with a locant.
胺是氨的衍生物，其中一个或多个氢被烷基或芳基取代。伯胺的命名是在烷基名称后加后缀“-amine”（如 ethylamine, C₂H₅NH₂）。当胺不是主官能团时，使用前缀“amino-”并标写位次。
Secondary and tertiary amines are named with the prefix N- to indicate substituents on the nitrogen atom (e.g., N-methylethanamine, CH₃NHCH₂CH₃). The longest carbon chain attached to nitrogen is used as the parent alkane. For diamines, the suffix '-diamine' is used.
仲胺和叔胺的命名用前缀 N- 表示氮原子上的取代基（如 N-methylethanamine, CH₃NHCH₂CH₃）。连接氮的最长碳链作为母体烷烃。对于二胺，使用后缀“-diamine”。
Amides feature the -CONH₂ group. The name ends in '-amide', and the numbering starts from the carbonyl carbon (C1). If substituted on nitrogen, use N-alkyl prefixes (e.g., N-methylethanamide).
酰胺含有 -CONH₂ 基团。名称以“-amide”结尾，编号从羰基碳 (C1) 开始。若氮上有取代，使用 N-烷基前缀（如 N-methylethanamide）。
11. Naming Aromatic Compounds | 芳香族化合物的命名
Many aromatic compounds use 'benzene' as the parent name. Monosubstituted benzenes are named by placing the substituent name before 'benzene' (e.g., chlorobenzene, nitrobenzene). Some common names are retained, like methylbenzene (toluene) and aminobenzene (aniline).
许多芳香族化合物以“苯”为母体命名。单取代苯的命名是将取代基名称置于“苯”之前（如 chlorobenzene, nitrobenzene）。部分常用名被保留，如甲基苯（甲苯，toluene）和氨基苯（苯胺，aniline）。
For disubstituted benzenes, locants 1,2-, 1,3- and 1,4- are used to show the relative positions. Alternatively, ortho- (o-), meta- (m-) and para- (p-) are accepted in many contexts. If the benzene ring is a substituent, it is called 'phenyl'. When a higher-priority functional group is directly attached to the ring, the compound may be named as a derivative of that group (e.g., benzoic acid, C₆H₅COOH).
对于二取代苯，使用 1,2-、1,3- 和 1,4- 表示相对位置。也可接受邻位 (ortho-/o-)、间位 (meta-/m-) 和对位 (para-/p-)。若苯环作为取代基，称为“phenyl”。当一个更高优先级的官能团直接连在环上，则可将该化合物命名为该基团的衍生物（如苯甲酸，benzoic acid, C₆H₅COOH）。
12. Complex Substituents and Branching | 复杂取代基和支链的命名
When side chains themselves contain branches or functional groups, they are named as complex substituents. Their numbering starts from the carbon directly attached to the parent chain. The complex substituent name is placed within parentheses, and prefixes like di-, tri- are still used for multiple identical complex substituents. The parent chain is chosen to give the main functional group the lowest number; if a tie, it should maximise the number of substituents.
当侧链本身含有支链或官能团时，需将其作为复杂取代基命名。其编号从与母链直接相连的碳开始。复杂取代基的名称置于括号中，如果存在多个相同复杂取代基，仍使用二、三等倍乘前缀。母链的选择应使主官能团获得最小编号；若平局，则应使取代基数目最多。
An example is 3-(1-methylethyl)heptane, where the isopropyl group is treated as a complex substituent (1-methylethyl). Alphabetical ordering considers the first letter of the substituent name ignoring the multiplier, but when multiple complex substituents are compared, the name inside the parenthesis is used for alphabetisation, ignoring any di-, tri- outside.
例如 3-(1-methylethyl)heptane，其中异丙基被作为复杂取代基 (1-methylethyl)。字母排序时不考虑倍乘前缀，但在比较多个复杂取代基时，使用括号内的名称进行排序，忽略外部的 di-, tri-。
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