Complex compounds in which a dumbbell shaped molecule is encircled by a macrocycle. They are named after rota (wheel) and axis (axle). Notation with a prefix is used to indicate the number of interlocked components. They have potential use in NANOTECHNOLOGY. Rotaxanes have been made with CYCLODEXTRINS and CYCLIC ETHERS.

Cyclobutanes are saturated hydrocarbons consisting of a four-carbon ring with only carbon-carbon sigma bonds, making up the smallest cycloalkane ring that can adopt a puckered conformation to alleviate angle strain. (25 words)