Which type of hydrocarbon compounds contain at least one double or triple bond between two adjacent carbon atoms?

Unsaturated hydrocarbons are characterized by the presence of at least one double bond or triple bond between adjacent carbon atoms. This structural feature distinguishes them from saturated hydrocarbons, which contain only single bonds between carbon atoms and are saturated with hydrogen atoms. Unsaturated hydrocarbons can include alkenes (which have at least one double bond) and alkynes (which contain a triple bond).

In contrast, aromatic compounds are a specific class of unsaturated hydrocarbons that feature a ring structure with delocalized pi electrons, contributing to their unique stability and chemical properties. Aliphatic compounds, while they can be saturated or unsaturated, refer more broadly to hydrocarbons that are not aromatic and may include both saturated and unsaturated forms.

Therefore, the defining characteristic of unsaturated hydrocarbons is their capacity to form double or triple bonds, making them an essential classification in the study of organic chemistry, particularly when learning about the reactivity and properties of different hydrocarbon types.