13.1
IUPAC Nomenclature of Carboxylic Acids
IUPAC names of carboxylic acids are systematically derived following a few rules discussed below.
For acyclic saturated monocarboxylic acids, the long…
Carboxylic acids are compounds with a –COOH functional group.
For the IUPAC nomenclature of monocarboxylic acids, identify the parent chain containing the –COOH carbon and replace the terminal -e of the corresponding alkane with the suffix -oic acid.
Number the chain from the –COOH end and identify the substituents and their locant values.
Lastly, assemble the name and indicate the stereochemistry.
In the case of unsaturation, the parent name derives from the corresponding alkene or alkyne.
To nomenclate dicarboxylic acids, select the parent chain that includes both the –COOH carbons and number from the end that gives the lowest locant to the substituents. Here, retain the terminal -e of the parent hydrocarbon and add the suffix -dioic acid.
If the –COOH group is bonded to a ring, -carboxylic acid is suffixed to the parent name, and the numbering begins from the ring carbon bearing the –COOH group.
In the presence of multiple –COOH groups, prefixes di- or tri- are used.
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Q1: How do you name a monocarboxylic acid using IUPAC nomenclature?
Identify the longest carbon chain containing the –COOH group as the parent chain. Replace the terminal -e of the corresponding alkane with the suffix -oic acid. Number the chain starting from the –COOH carbon, identify substituents and their positions, then assemble the complete name with stereochemistry if needed.
Q2: What is the difference between naming monocarboxylic and dicarboxylic acids?
For dicarboxylic acids, select the parent chain including both –COOH carbons and number to give substituents the lowest locants. Retain the terminal -e of the parent hydrocarbon and add the suffix -dioic acid, unlike monocarboxylic acids where the terminal -e is replaced with -oic acid.
Q3: How are unsaturated carboxylic acids named?
Unsaturated carboxylic acids derive their parent name from the corresponding alkene or alkyne. The position of the double or triple bond is indicated by a locant prefixed to the parent name. Stereochemistry around double bonds is shown using cis/trans or E/Z notation prefixed to the parent name.
Q4: What priority do carboxylic acid groups have over other functional groups?
The –COOH group has the highest priority among functional groups. All other groups like –CHO, –CO–, –OH, –OR, –NH2, and halogens are treated as substituents when a carboxylic acid is present and are named as prefixes to the parent name.
Q5: How are cyclic carboxylic acids named?
When a –COOH group is bonded directly to a cycloalkane or aromatic ring, the suffix -carboxylic acid is added to the parent ring name. The ring carbon bearing the –COOH group is numbered as carbon-1, unlike acyclic carboxylic acids where numbering starts from the carboxylic acid carbon.
Q6: What naming convention is used for compounds with three or more carboxylic acid groups?
Compounds with multiple –COOH groups use prefixes di- or tri- to indicate the number of carboxylic acid groups. Sometimes one carboxylic acid is treated as the main functional group while others are named as substituents using prefixes like carboxymethyl- to the parent name.
Q7: Why is numbering direction important when naming dicarboxylic acids?
When naming dicarboxylic acids, the parent chain must be numbered from the end that gives substituents the lowest locant values. This ensures the most systematic and unambiguous name, following IUPAC rules for locant assignment and maintaining consistency in nomenclature across all carboxylic acid structures.