Cyclopropanes are a family of

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s containing the cyclopropyl group. The parent is

cyclopropane Cyclopropane is the cycloalkane with the molecular formula (CH2)3, consisting of three methylene groups (CH2) linked to each other to form a triangular ring. The small size of the ring creates substantial ring strain in the structure. Cyclopropane ...

().

Synthesis and reactions

Most cyclopropanes are not prepared from the parent cyclopropane, which is somewhat inert. Instead, yclopropyl groups are often prepared by cyclization of 1,3-difunctional

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in whi ...

s. An example of the former,

cyclopropyl cyanide Cyclopropyl cyanide is an organic compound consisting of a nitrile group as a substituent on a cyclopropane ring. It is the smallest cyclic compound containing a nitrile. Structure The structure of cyclopropyl cyanide has been determined by a va ...

is prepared by the reaction of 4- chlorobutyronitrile with a

strong base In chemistry, there are three definitions in common use of the word "base": '' Arrhenius bases'', '' Brønsted bases'', and '' Lewis bases''. All definitions agree that bases are substances that react with acids, as originally proposed by G. ...

. Phenylcyclopropane is produced analogously from the 1,3-dibromide. A second major route to cyclopropanes entails addition of methylene (or its substituted derivatives) to an

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

, a process called

cyclopropanation In organic chemistry, cyclopropanation refers to any chemical process which generates cyclopropane () Ring (chemistry), rings. It is an important process in modern chemistry as many useful compounds bear this motif; for example pyrethroid insectic ...

. Substituted cyclopropanes undergo the reactions associated with the cyclopropyl ring or the substituents. Vinylcyclopropanes are a special case as they undergo

vinylcyclopropane rearrangement The vinylcyclopropane rearrangement or vinylcyclopropane-cyclopentene rearrangement is a ring expansion reaction, converting a vinyl-substituted cyclopropane ring into a cyclopentene ring. Cyclopropyl groups adjacent to vinyl groups can undergo ri ...

Simple substituted cyclopropanes

* Chlorocyclopropane * Cyclopropane carboxylic acid * Cyclopropyl amine *

Cyclopropyl cyanide Cyclopropyl cyanide is an organic compound consisting of a nitrile group as a substituent on a cyclopropane ring. It is the smallest cyclic compound containing a nitrile. Structure The structure of cyclopropyl cyanide has been determined by a va ...

* Cyclopropanol

Applications and occurrence

Cyclopropane derivatives are numerous. Many

biomolecule A biomolecule or biological molecule is loosely defined as a molecule produced by a living organism and essential to one or more typically biological processes. Biomolecules include large macromolecules such as proteins, carbohydrates, lipids ...

s and

pharmaceutical drug Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the ...

s feature the cyclopropane ring. Famous example is aminocyclopropane carboxylic acid, which is the precursor to

ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...

, a plant hormone. The

pyrethroid A pyrethroid is an organic compound similar to the natural pyrethrins, which are produced by the flowers of pyrethrums (''Chrysanthemum cinerariaefolium'' and ''Chrysanthemum coccineum, C. coccineum''). Pyrethroids are used as commercial and hou ...

s are the basis of many

insecticide Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...

s. Several

cyclopropane fatty acid Cyclopropane fatty acids (CPA) are a subgroup of fatty acids that contain a cyclopropane group. Although they are usually rare, the seed oil from lychee contains nearly 40% CPAs in the form of triglycerides. Biosynthesis CPAs are derived from u ...

s are known. : left, 122 px, 1-Aminocyclopropane-1-carboxylic acid plays an important role in the biosynthesis of the plant hormone ethylene.

References

{{Cycloalkanes *