Cycloalkane Foundations

Cycloalkane

A saturated hydrocarbon in which carbon atoms are connected to form a ring.

Alicyclic Compound

A cyclic organic compound that behaves like an aliphatic rather than an aromatic compound; cycloalkanes are alicyclic compounds.

Cycloalkane Ring

A closed carbon chain formed when the two ends of a carbon chain are connected.

Saturated Cycloalkane

A cycloalkane containing only carbon-carbon single bonds and carbon-hydrogen bonds.

General Formula of a Monocyclic Cycloalkane

CₙH₂ₙ, where n is the number of carbon atoms in a saturated compound containing one ring.

Why do monocyclic cycloalkanes have the formula CₙH₂ₙ instead of CₙH₂ₙ₊₂?

Closing an acyclic alkane chain into one ring forms an additional C–C bond and results in two fewer hydrogen atoms.

Cycloalkane Naming Principle

Add the prefix cyclo- to the name of the corresponding alkane having the same number of carbon atoms.

cyclo-

The prefix indicating that the carbon skeleton forms a ring.

Cyclopropane

A three-carbon cycloalkane with molecular formula C₃H₆.

Cyclobutane

A four-carbon cycloalkane with molecular formula C₄H₈.

Cyclopentane

A five-carbon cycloalkane with molecular formula C₅H₁₀.

Cyclohexane

A six-carbon cycloalkane with molecular formula C₆H₁₂.

Polygon Representation of a Cycloalkane

A skeletal representation in which the polygon vertices represent carbon atoms and its edges represent carbon-carbon bonds.

Carbon Representation in a Cycloalkane Polygon

Each corner or vertex represents one carbon atom.

Hydrogen Representation in a Cycloalkane Polygon

Hydrogens bonded to carbon are normally omitted and are understood to complete carbon's valence of four.

Ring Size

The number of atoms forming the ring; for a simple cycloalkane, it equals the number of carbon vertices in its polygon representation.

Cyclopropane Ring Representation

Triangle

Cyclobutane Ring Representation

Square

Cyclopentane Ring Representation

Pentagon

Cyclohexane Ring Representation

Hexagon

Cycloalkane vs. Open-Chain Alkane

A cycloalkane contains a closed carbon ring, whereas an open-chain alkane has carbon-chain ends that are not connected.