Alcohols and phenols are key players in organic chemistry, sporting the iconic hydroxyl group. These compounds come in various flavors, from simple primary alcohols to complex phenols with multiple substituents. Naming them can be tricky, but IUPAC rules provide a clear roadmap.

Mastering alcohol and phenol nomenclature is crucial for understanding their structure and reactivity. The position of the hydroxyl group and other substituents greatly influences a compound's properties. This knowledge forms the foundation for exploring more complex organic molecules and their reactions.

Naming Alcohols

IUPAC naming of alcohols

• Identify the longest continuous carbon chain that includes the carbon bonded to the hydroxyl group (-OH)
  • When multiple longest chains exist, select the one with the greatest number of substituents (ethanol)
• Number the carbon atoms in the chain consecutively, starting from the end nearest to the hydroxyl group
• Categorize the alcohol as primary (1°), secondary (2°), or tertiary (3°) based on the number of carbon atoms directly attached to the carbon bonded to the hydroxyl group
  • Primary (1°) has one carbon attached (1-propanol)
  • Secondary (2°) has two carbons attached (2-butanol)
  • Tertiary (3°) has three carbons attached (2-methyl-2-propanol)
• Append the suffix "-ol" to the end of the name to signify the presence of a hydroxyl group
• Specify the location of the hydroxyl group by including the number of the carbon atom to which it is bonded
• Name any substituents and indicate their positions using the appropriate numbers
• Construct the name in the following sequence: substituents in alphabetical order, number denoting hydroxyl position, base name of the longest carbon chain, and "-ol" suffix (3-methyl-1-butanol)
• IUPAC nomenclature rules ensure consistent and unambiguous naming of organic compounds

Hydroxyl group positioning in alcohols

• Locate the longest carbon chain that contains the hydroxyl group
• Number the carbon atoms in the chain consecutively, beginning from the end that results in the hydroxyl group having the lowest possible number
  • If the hydroxyl group is equidistant from both ends, start numbering from the end that assigns the lowest numbers to the substituents (2,3-dimethyl-2-butanol)
• Assign numbers to the hydroxyl group and any substituents to indicate their positions on the carbon chain
• When multiple hydroxyl groups are present, use the suffixes "-diol", "-triol", etc., and specify their locations using numbers (1,2-ethanediol)
• If the compound contains a hydroxyl group and a higher-priority functional group (carboxylic acid, aldehyde), use the suffix corresponding to the higher-priority group and denote the hydroxyl group as a substituent with the prefix "hydroxy-" (3-hydroxybutanoic acid)
• Consider isomerism when naming alcohols, as different structural arrangements can lead to distinct compounds

Naming Phenols

Phenol nomenclature vs aromatics

• Identify the benzene ring with the hydroxyl group directly attached
• If the hydroxyl group is the only substituent, simply name the compound "phenol"
• When substituents are present, number the carbon atoms on the benzene ring
  • Begin numbering from the carbon bonded to the hydroxyl group and proceed clockwise or counterclockwise, whichever assigns the lowest numbers to the substituents (3-methylphenol)
• Name the substituents and indicate their positions using the appropriate numbers
• Arrange the name as follows: numbers indicating substituent positions, substituent names in alphabetical order, and "phenol" (2-chloro-4-methylphenol)
• If the compound contains a higher-priority functional group (carboxylic acid, aldehyde), use the suffix for that group and denote the hydroxyl group as a substituent with the prefix "hydroxy-" (4-hydroxybenzoic acid)
• Understand the concept of aromaticity and its impact on the properties and reactivity of phenols

Functional Groups and Organic Acids

• Alcohols and phenols are important functional groups in organic chemistry
• The hydroxyl group (-OH) is the defining feature of both alcohols and phenols
• Organic acids, such as carboxylic acids, contain a carboxyl group (-COOH) and exhibit different properties compared to alcohols and phenols
• Understanding the relationship between functional groups helps in predicting chemical behavior and reactivity