Cyclobutane is a cycloalkane and organic compound with the formula (CH2)4. Cyclobutane is a colorless gas that is commercially available as a liquefied gas. The derivatives of cyclobutane are called cyclobutane. Cyclobutane itself has no commercial or biological interest, but more complex derivatives are important in biology and biotechnology.

The bond angles between carbon atoms are significantly strained and thus have lower bond energies compared to related straight-chain or unstrained hydrocarbons such as hydrocarbons. butane or cyclohexane. Therefore, cyclobutane is unstable above about 500 °C.

The four carbon atoms in cyclobutane are not coplanar; instead, the rings typically adopt a folded or "pleated" configuration. [2] This means that the C-C-C angle is less than 90°. One of the carbon atoms is at a 25° angle to the plane formed by the other three carbon atoms. In this way, some shadowing interactions are reduced. This configuration is also known as a "butterfly". The equivalent folded conformations are interconverted:

Despite the inherent stress, cyclobutane sequences do occur in nature. An unusual example is pentacycline,[3] which is a ladder consisting of 5 fused cyclobutane units. The estimated strain of this compound is 3 times that of cyclobutane. This compound is found in bacteria that perform the anammox process, and it forms part of a tight and very dense membrane that is believed to protect the organism from the toxic hydroxylamine and hydrazine involved in the conversion of nitrite Nitrogen and water are produced from ions and ammonia. [4] Some related fenestranes are also found in nature. [citation needed]