cycloalkane

Also known as cyclanes or polymethylenes, cycloalkanes are alkanes with a ring rather than a chain connectivity. Each ring position is equivalent (unless the ring is substituted) and each carbon atom is bonded to two hydrogen atoms.

The simplest cycloalkane is cyclopropane:

 
  H       H
   \     /
H - C - C - H
     \ /
      C
     / \
    H   H

The general formula of cycloalkanes is C_nH_2n.

Closely related are the cycloalkenes, which contain a double bond between carbon atoms (C=C). The simplest is cyclopropene:

H       H
 \     /  
  C = C 
   \ /
    C
   / \
  H   H

Cycloalkanes and cycloalkenes generally behave similarly to straight-chain alkanes and alkenes.

It should be noted that, unlike benzene rings, cycloalkane rings are not planar. The optimal geometry for each carbon atom in a cycloalkane is tetrahedral, so the rings adopt a "puckered" shape, most importantly the "chair" shape of cyclohexane.