How can alcohols be defined?

Alcohols can be defined as a homologous series of alkanols. This means they share a common structural feature, specifically the presence of one or more hydroxyl (-OH) functional groups attached to a carbon atom. The term "homologous series" indicates that alcohols follow a predictable pattern in their physical and chemical properties as the number of carbon atoms increases.

As you progress through the series, you can observe a gradual change in the boiling points, solubility, and reactivity due to the increasing length of the carbon chain and the influence of the hydroxyl group. Each member of the series differs from the next by a constant unit, generally a -CH2- group, which reinforces the idea of a homologous series.

The other options do not accurately define alcohols: carbohydrates refer to a different group of organic compounds, mainly sugars and starches; alkanes are a separate class of hydrocarbons that only contain single bonds between carbon atoms and lack the -OH functional group; and aromatic compounds contain a specific cyclic structure with delocalized electrons, such as benzene, which does not apply to alcohols. Hence, defining alcohols as a homologous series of alkanols is precise and encompassing of their chemical nature