3.8: Cicloalcanos
Cycloalkanes are saturated cyclic hydrocarbons with carbon atoms arranged in the form of rings. They have two fewer hydrogen atoms than the corresponding acyclic alkane; therefore, their general formula is CnH2n. The structural formulas of cycloalkanes are simplified using the line-angle representation. The regular polygons are used to represent the cycloalkane rings, with each side representing a carbon-carbon bond.
The IUPAC nomenclature of cycloalkanes follows similar rules that apply to open-chain alkanes with few minor variations. The prefix “cyclo” is added to the corresponding open-chain name to indicate the presence of a ring. A monosubstituted cycloalkane is named by adding the substituent name before the parent name without specifying the locant. For cycloalkanes with multiple identical or non-identical substituents, the locant values are assigned in such a way that the substituents receive the lowest set of values. If the substituent has more carbon atoms than the ring, the name of the cyclic part is written before the acyclic part. However, as per the updated IUPAC rules,1 irrespective of the carbon atoms, the ring always receives preference, and hence, it is considered the parent.
Bicycloalkanes are formed by fusing two rings that share two carbon atoms known as bridgeheads. They have two fewer hydrogens than the cycloalkanes and hence have the general formula CnH2n-2.
