Alkanes Cycloalkanes 十十 small three-and four-membered rings are reactive and behave like alkenes. Such cyclic structures are highly strained since it is impossible for the carbon atoms to adopt their preferred tetrahedral shape.Alkanes & Cycloalkanes ™small three- and four-membered rings are reactive and behave like alkenes. ™Such cyclic structures are highly strained since it is impossible for the carbon atoms to adopt their preferred tetrahedral shape