An alicyclic compound is an organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 that is both aliphatic

Aliphatic compound

In organic chemistry, aliphatic compounds are acyclic or cyclic, non-aromatic carbon compounds.Thus, aliphatic compounds are opposite to aromatic compounds.- Structure :...

 and cyclic

Cyclic compound

In chemistry, a cyclic compound is a compound in which a series of atoms is connected to form a loop or ring.While the vast majority of cyclic compounds are organic, a few inorganic substances form cyclic compounds as well, including sulfur, silanes, phosphanes, phosphoric acid, and triboric acid. ...

. They contain one or more all-carbon rings which may be either saturated

Saturation (chemistry)

In chemistry, saturation has six different meanings, all based on reaching a maximum capacity...

 or unsaturated, but do not have aromatic

Aromaticity

In organic chemistry, Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. The earliest use of the term was in an article by August...

 character. Alicyclic compounds may or may not have aliphatic side chains attached.

The simplest alicyclic compounds are the monocyclic cycloalkane

Cycloalkane

Cycloalkanes are types of alkanes that have one or more rings of carbon atoms in the chemical structure of their molecules. Alkanes are types of organic hydrocarbon compounds that have only single chemical bonds in their chemical structure...

s: cyclopropane

Cyclopropane

Cyclopropane is a cycloalkane molecule with the molecular formula C3H6, consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms...

, cyclobutane

Cyclobutane

Cyclobutane is an organic compound with the formula 4. Cyclobutane is a colourless gas and commercially available as a liquefied gas. Derivatives of cyclobutane are called cyclobutanes...

, cyclopentane

Cyclopentane

Cyclopentane is a highly flammable alicyclic hydrocarbon with chemical formula 510 and CAS number 287-92-3, consisting of a ring of five carbon atoms each bonded with two hydrogen atoms above and below the plane. It occurs as a colorless liquid with a petrol-like odor. Its melting point is −94 °C...

, cyclohexane

Cyclohexane

Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which being intermediates used in the production of nylon...

, cycloheptane

Cycloheptane

Cycloheptane is a cycloalkane with the molecular formula C7H14. Cycloheptane is used as a nonpolar solvent for the chemical industry and as an intermediate in the manufacture of chemicals and pharmaceutical drugs. It may be derived by Clemmensen reduction from cycloheptanone. Cycloheptane vapour is...

, cyclooctane

Cyclooctane

Cyclooctane is a cycloalkane with the molecular formula 8. It is a simple colourless hydrocarbon, but it is often a reference compound for saturated eight-membered ring compounds in general.- Conformation :...

, cyclononane

Cyclononane

Cyclononane is an alicyclic hydrocarbon consisting of a ring of nine carbon atoms. Its molecular formula is C9H18. Its empirical formula is CH2....

, cyclodecane

Cyclodecane

Cyclodecane is a cycloalkane with the chemical formula C10H20....

, cycloundecane

Cycloundecane

Cycloundecane is a saturated cyclic organic compound with eleven carbon atoms forming a ring. It is classed as an alkane because it has only carbon and hydrogen and these elements are configured with C-H and C-C such that there is a chain of carbon atoms with hydrogens attached to them...

, cyclododecane

Cyclododecane

Cyclododecane is an organic compound with the chemical formula C12H24.Cyclododecane is mainly used as an intermediate in production of flame retardants, detergents, and other chemicals....

, and so on. Bicyclic

Bicyclic molecule

A bicyclic molecule is a molecule that features two fused rings. Bicyclic molecules occur widely in organic and inorganic compounds.Fusion of the rings can occur in three ways:...

 alkanes include bicycloundecane

Bicycloundecane

Bicycloundecane is an organic compound with molecular formula C11H20. It is essentially the spherical form of the ring cycloundecane. In cycloundecane, the eleven carbon atoms are joined together in a chain that meets at the ends to form a ring...

 and decalin. Polycyclic

Polycyclic compound

In organic chemistry, a polycyclic compound is a cyclic compound with more than one hydrocarbon loop or ring structures . In general, the term includes all polycyclic aromatic compounds, including the polycyclic aromatic hydrocarbons, the heterocyclic aromatic compounds containing sulfur,...

 alkanes include cubane

Cubane

Cubane is a synthetic hydrocarbon molecule that consists of eight carbon atoms arranged at the corners of a cube, with one hydrogen atom attached to each carbon atom. A solid crystalline substance, cubane is one of the Platonic hydrocarbons. It was first synthesized in 1964 by Philip Eaton, a...

, basketane

Basketane

Basketane is a polycyclic alkane with the chemical formula C10H12. The name is taken from its structural similarity to a basket shape. Basketane was first synthesised in 1966, independently by Masamune and Dauben and Whalen.-Further reading:...

, and housane

Housane

Housane, with formula C10H10, is poli cyclic alkane. It was named housane because of its shape.IUPAC name: hexacyclo[5.3.0.02,6.03,10.04,9.05,8]decane...

.

Spiro compound

Spiro compound

A spiro compound is a bicyclic organic compound with rings connected through just one atom. The rings can be different in nature or identical. The connecting atom is also called the spiroatom, most often a quaternary carbon...

s have two or more rings that are connected through only one carbon atom.

An exocyclic group is always shown outside the ring structure, take for instance the exocyclic double bond on the left:

See for an example isotoluene

Isotoluene

The isotoluenes in organic chemistry are the non-aromatic toluene isomers with an exocyclic double bond. They are of some academic interest in relation to aromaticity and isomerisation mechanisms....

.

The placement of double bonds in many alicyclic compounds can be predicted with Bredt's rule

Bredt's Rule

Bredt's rule is an empirical observation in organic chemistry that states that a double bond cannot be placed at the bridgehead of a bridged ring system, unless the rings are large enough...

.

The mode of ring-closing in the formation of many alicyclic compounds can be predicted by Baldwin's rules

Baldwin's rules

Baldwin's Rules in organic chemistry are a series of guidelines outlining the relative favourabilities of ring closure reactions in alicyclic compounds. They were first proposed by Jack Baldwin in 1976...

.

Cycloalkenes

Monocyclic cycloalkene

Cycloalkene

A cycloalkene or cycloolefin is a type of alkene hydrocarbon which contains a closed ring of carbon atoms, but has no aromatic character. Some cycloalkenes, such as cyclobutene and cyclopentene, can be used as monomers to produce polymer chains. Unless the rings are very large, cycloalkenes are...

s are cyclopropene

Cyclopropene

Cyclopropene is an organic compound with the formula 34. It is the simplest isolable cycloalkene. It has a triangular structure. Because the ring is highly strained, cyclopropene is both difficult to prepare and interesting to study. Like cyclopropane, the carbon ring of cyclopropene is planar...

, cyclobutene

Cyclobutene

Cyclobutene is a cycloalkene. It is used in the chemical industry as a monomer for synthesis of some polymers and for a range of chemical syntheses.- External links :*...

, cyclopentene

Cyclopentene

Cyclopentene is a chemical compound with the formula 58. It is a colorless liquid with a petrol-like odor. It is one of the cycloalkenes.Cyclopentene is produced industrially in large amounts...

, cyclohexene

Cyclohexene

Cyclohexene is a hydrocarbon with the formula C6H10. This cycloalkene is a colorless liquid with a sharp smell. It is an intermediate in various industrial processes...

, cycloheptene

Cycloheptene

Cycloheptene is a 7-membered cycloalkene with a flash point of -6 C°. It is a raw material in organic chemistry and a monomer in polymer synthesis. Cycloheptene can exist as either the cis- or the trans-isomer.- trans-Cycloheptene :...

, cyclooctene

Cyclooctene

Cyclooctene is a cycloalkene with an eight-membered ring. It is notable because it is the smallest cycloalkene that can exist as either the cis- or trans-isomer with the cis-isomer more common...

, and so on. Bicyclic alkenes include norbornene

Norbornene

Norbornene or norbornylene or norcamphene is a bridged cyclic hydrocarbon. It is a white solid with a pungent sour odor. The molecule consists of a cyclohexene ring bridged with a methylene group in the para position...

 and norbornadiene

Norbornadiene

Norbornadiene is an organic compound. This bicyclic hydrocarbon is the most stable diolefin derived from the norbornane and norbornene. Norbornadiene is primarily of interest as a ligand in homogeneous catalysis, but it has been heavily studied due to its high reactivity and distinctive...

.