C18H36

C18H36 is a hydrocarbon composed of 18 carbon atoms and 36 hydrogen atoms. It is a saturated monocyclic hydrocarbon, meaning it has a single carbon ring and no carbon–carbon double bonds, which gives it a degree of unsaturation of 1.

As a member of the cycloalkanes, C18H36 denotes a family of isomeric structures. The simplest representative is cyclooctadecane, in which all 18 carbons form one ring. However, many monocyclic isomers are possible in which the ring contains fewer than 18 carbons and the remaining carbons appear as alkyl substituents attached to the ring. The specific arrangement influences physical properties such as melting and boiling behavior, density, and branching.

Occurrence and production: These compounds occur within complex petroleum mixtures and refined products as part of the heavier hydrocarbon fractions. They can be produced by cyclization reactions during petrochemical processing and by rearrangement or isomerization of alkanes, with separation typically achieved by distillation or chromatography.

Properties and uses: They are nonpolar and poorly soluble in water, generally existing as liquids or waxy solids depending on the exact isomer. Their applications are mostly in fuels, lubricants, or as reference standards in analytical chemistry. Their chemical reactivity is low due to the saturated nature of the C–C bonds, and they are flammable.

Molar mass and naming: The approximate molar mass is 252.5 g/mol. The IUPAC name for the fully cyclized form is cyclooctadecane; other isomers may be described as substituted cycloalkanes, reflecting different ring sizes and alkyl substituents.

In summary, C18H36 designates a monocyclic, saturated hydrocarbon family with 18 carbons, exemplified by cyclooctadecane, with numerous possible isomers and practical relevance to petroleum chemistry.