cycloalkane

Cycloalkanes are saturated hydrocarbons that contain one or more rings of carbon atoms. The monocyclic cycloalkanes have the general formula CnH2n, where n is the number of carbon atoms in the ring. Common examples include cyclopropane, cyclobutane, cyclopentane and cyclohexane. They are nonpolar and predominantly unreactive relative to many other hydrocarbons, with all carbon atoms in an sp3 hybridization state.

Structure and conformations play a key role in cycloalkane chemistry. Small rings experience angle strain because the ideal tetrahedral bond angle is 109.5 degrees, but cyclopropane and cyclobutane force smaller angles. Cyclohexane, in contrast, adopts a chair conformation that minimizes strain and achieves favorable staggered arrangements of bonds. This variation in ring strain influences boiling points, reactivity, and stability across the series.

Nomenclature generally treats the ring as the parent structure, using cyclo- as a prefix. Substituents are numbered to give the lowest possible set of locants. If multiple rings or fused rings are present, more specialized naming (such as bicyclic or polycyclic system names) is used.

Reactivity of cycloalkanes is dominated by typical alkane-like chemistry: they undergo free-radical halogenation, hydrogenation of double bonds in cycloalkenes, combustion, and certain ring-opening reactions under strong conditions. Ring strain in the smallest rings can lead to enhanced reactivity, whereas larger rings tend to be more thermodynamically stable.

Applications include use as nonpolar solvents and starting materials in organic synthesis. Cycloalkanes also occur as components of crude oil and serve as building blocks for more complex molecules in pharmaceuticals, polymers, and industrial chemistry.