Alifatiskt

Alifatiskt is a term used in organic chemistry to describe compounds that are non-aromatic. The category includes molecules in which the carbon skeleton forms open chains or non-aromatic rings. It contrasts with aromatic compounds, which contain one or more benzene-like rings with delocalized pi electrons. Aliphatic compounds can be saturated (alkanes), unsaturated (alkenes, alkynes), or non-aromatic cyclic structures (cycloalkanes) and may contain heteroatoms.

Common examples include methane, ethane, and butane (alkanes); ethene and propene (alkenes); acetylene (alkyne); cyclohexane (cycloalkane); and non-aromatic heterocycles such as piperidine. These illustrate the diversity of aliphatic structures, from simple linear chains to ring-containing systems that are not aromatic.

Properties of aliphatic compounds are often governed by size, shape, and branching. They are typically nonpolar or weakly polar, with boiling and melting points that rise with molecular weight; branching tends to lower boiling points. Reactivity varies: alkanes undergo free-radical halogenation and combustion; alkenes and alkynes participate in numerous addition reactions; cycloalkanes undergo reactions similar to their acyclic counterparts, with potential ring strain influencing outcomes. Functional groups appended to the aliphatic skeleton define specific reactivity patterns.

Occurrence and applications are broad. Aliphatic compounds are major components of fuels and solvents, and serve as building blocks in the petrochemical industry. They provide precursors for polymers, lubricants, and various industrial chemicals, forming a foundational category in organic synthesis and materials science.

Note that in modern chemistry, the term aliphatic is used less as a strict category and more as an umbrella label for non-aromatic hydrocarbon-like character, with chemists often naming specific classes such as alkanes, alkenes, or cycloalkanes instead.