Cycloalkanes are alkanes that have the chain ends joined together, forming a cycle. They have two fewer hydrogens than the alkane from which they are derived, which is why their molecular formula is CnH2n . They are named using the prefix cyclo followed by the name of the alkane.

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[1] Cyclopropane

[2] Cyclobutane

[3] Cyclopentane

[4] Cyclohexane

It is common to represent molecules indicating only their skeleton. Each vertex represents a carbon bonded to two hydrogens.

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The IUPAC rules for naming cycloalkanes are very similar to those studied for alkanes.

Rule 1.- In cycloalkanes with a single substituent, the cycle is taken as the main chain of the molecule. Cycle numbering is unnecessary.

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[4] Ethylcyclobutane

[5] Isopropylcyclohexane

[5] Methylcyclopentane

If the side chain is complex, it can be taken as the main chain of the molecule and the cycle as a substituent. Cycloalkanes as substituents are named by changing the ending –ane to –yl.

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[7] Cyclopropyl

[8] Cyclobutyl

[9] Cyclopentyl



Rule 2.- If the cycloalkane has two substituents, they are named in alphabetical order. The cycle is numbered starting with the substituent that comes before it in the name.


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[11] 3-Cyclopropyl-2-methyloctane

[12] 1-Cyclopentyl-3-methylhexane

Rule 3.- If the ring has three or more substituents, they are named in alphabetical order. The numbering of the cycle is done in such a way that the lowest locants are given to the substituents.


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[14] 1-Bromo-2-ethyl-4-methylcyclopentane

[15] 2-Bromo-1-chloro-3-methylcyclopentane

In case of obtaining the same locants when numbering starting with different positions, the alphabetical order is taken into account.

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[16] 1-Ethyl-3-methylcyclopentane

[17] 1-Bromo-3-chlorocyclohexane