Alcohols can be named using common names, which is a straightforward method especially useful for simple alcohols. This naming convention involves stating the name of the alkyl group attached to the hydroxyl (–OH) group, followed by the word "alcohol." For example, an alcohol with a methyl group is called methyl alcohol, one with a propyl group is propyl alcohol, and one with a hexyl group is hexyl alcohol. This approach emphasizes the alkyl portion of the molecule first, making it easy to identify the structure based on the alkyl chain length and the presence of the alcohol functional group.
14. Compounds with Oxygen or Sulfur
Naming Alcohols (Common Names)
14. Compounds with Oxygen or Sulfur
Naming Alcohols (Common Names): Videos & Practice Problems
Topic summary
Naming Alcohols (Common Names) focuses on a simple pattern used for many small or simple alcohols. The common name is written as the alkyl group name followed by the word alcohol. In other words, identify the carbon group attached to the hydroxyl-containing carbon framework, convert that carbon portion into its alkyl name, and then place alcohol after it.
To apply this correctly, first recognize the structure of the alkyl group. A straight-chain carbon group gives names such as butyl, propyl, or hexyl, while branched groups must keep their correct common alkyl names, such as isobutyl. If the OH group is attached to a ring, use the prefix cyclo, count the carbons in the ring, name the ring as a cycloalkyl group, and then add alcohol. This makes common alcohol naming a matter of identifying whether the attached group is straight-chain, branched, or cyclic and then writing alkyl name + alcohol.
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Concept
Naming Alcohols (Common Names) Concept 1
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38sNaming Alcohols (Common Names) Concept 1 Video Summary
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Example
Naming Alcohols (Common Names) Example 1
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45sNaming Alcohols (Common Names) Example 1 Video Summary
When naming alcohols using their common names, the key step is to identify the length of the alkyl group attached to the hydroxyl (–OH) group. For example, if the alcohol has a straight chain of four carbon atoms, the alkyl group is called "butyl." Since the compound contains an –OH group, the name ends with "alcohol." Therefore, a four-carbon straight-chain alcohol is commonly named butyl alcohol. This approach simplifies naming by focusing on the alkyl group and appending "alcohol" to indicate the presence of the hydroxyl functional group.
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Problem
Provide common name for the following alcohol compound.
A
2-methyl-1-propanol.
B
Tert-butyl alcohol.
C
Isobutyl alcohol.
D
Propyl alcohol.
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Problem
What is the common name for this alcohol?
A
Pentyl alcohol.
B
Cyclohexyl alcohol.
C
Cyclopropyl alcohol.
D
Cyclopentyl alcohol.
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The basic rule for naming simple alcohols using common names is to first identify the alkyl group attached to the hydroxyl (OH) group and then add the word "alcohol" after it. This means the name consists of the alkyl group name followed by "alcohol." For example, if the alkyl group is methyl, the common name is methyl alcohol; if it is propyl, the name is propyl alcohol. This naming system is straightforward and focuses on recognizing the carbon chain or group bonded to the OH group before appending "alcohol." It is mainly used for simple alcohols and is different from the IUPAC system, which uses the suffix "-ol."
When the hydroxyl group is attached to a branched alkyl group, the common name still follows the pattern of alkyl name + "alcohol," but the alkyl group name reflects the branching. For example, a four-carbon branched alkyl group might be named "isobutyl," so the alcohol would be called isobutyl alcohol. The key is to recognize the branching pattern in the carbon skeleton and use the appropriate alkyl group name that describes the structure. This helps distinguish it from straight-chain alkyl groups like butyl alcohol. Understanding the structure of the carbon framework is essential to correctly naming branched alcohols using common names.
When the hydroxyl group is attached to a ring structure, the common name includes the prefix "cyclo" to indicate the ring, followed by the name of the ring and then "alcohol." For example, if the ring is a five-carbon ring, the name would be cyclopentyl alcohol. The ring is treated as the alkyl group, and the carbons in the ring are counted to determine the ring name. This naming method emphasizes recognizing the ring as the alkyl portion and then adding "alcohol" to indicate the presence of the hydroxyl group. This approach is useful for naming cyclic alcohols in a simple and clear way.
The main difference between common names and IUPAC names for alcohols lies in their naming conventions. Common names are formed by naming the alkyl group attached to the hydroxyl group followed by the word "alcohol" (e.g., methyl alcohol, propyl alcohol). This system is simpler and often used for simple alcohols. In contrast, IUPAC names use the parent hydrocarbon chain and replace the terminal hydrogen with the suffix "-ol" to indicate the alcohol functional group (e.g., methanol, propanol). IUPAC names also include numbering to indicate the position of the hydroxyl group if necessary. While common names focus on the alkyl group, IUPAC names provide a systematic and standardized way to name all alcohols, including complex ones.
Recognizing the carbon skeleton before naming an alcohol using common names is important because the alkyl group name depends on the structure of the carbon framework attached to the hydroxyl group. Whether the carbon chain is straight, branched, or part of a ring affects the alkyl name used. For example, a straight four-carbon chain is called butyl, while a branched four-carbon chain might be isobutyl. If the alcohol is attached to a ring, the prefix "cyclo" is added. Correctly identifying the carbon skeleton ensures the proper alkyl name is chosen, which is essential for accurately naming the alcohol in the common naming system. This step helps avoid confusion and ensures clarity in communication.
