What primarily influences the properties of alcohols and phenols, and how do alkyl/aryl groups modify these properties?

The properties of alcohols and phenols are primarily influenced by the presence of the hydroxyl (-OH) group. The polar nature of the hydroxyl group imparts hydrogen bonding capabilities, affecting boiling points and solubility. Alkyl or aryl groups attached to the hydroxyl-bearing carbon significantly modify these properties. In alcohols, alkyl groups increase hydrophobicity, reducing solubility in water. Longer alkyl chains enhance van der Waals forces, raising boiling points. Phenols exhibit greater acidity due to resonance stabilization of the phenoxide ion. Substituents on the phenol ring influence acidity and reactivity. Overall, the nature and size of substituents play a crucial role in shaping the physical and chemical properties of alcohols and phenols.