Cyclopentyne is a

cycloalkyne In organic chemistry, a cycloalkyne is the cyclic analog (chemistry), analog of an alkyne (). A cycloalkyne consists of a closed Ring (chemistry), ring of carbon atoms containing one or more triple bonds. Cycloalkynes have a general formula Becau ...

containing five

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

atoms in the ring. Due to the ideal

bond angle Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that deter ...

of 180° at each atom of the

alkyne \ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...

but the structural requirement that the bonds form a ring, this chemical is a highly strained structure, and the triple bond is highly reactive. The triple bond easily undergoes both +2and +2

cycloaddition In organic chemistry, a cycloaddition is a chemical reaction in which "two or more Unsaturated hydrocarbon, unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of th ...

reactions. Unlike benzyne, which undergoes a +2addition with loss of

stereochemistry Stereochemistry, a subdiscipline of chemistry, studies the spatial arrangement of atoms that form the structure of molecules and their manipulation. The study of stereochemistry focuses on the relationships between stereoisomers, which are defined ...

at the alkene partner, cyclopentyne reacts with alkenes with retention of geometry of the partner, an example of the relevance of

orbital symmetry In chemistry, molecular symmetry describes the symmetry present in molecules and the classification of these molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can be used to predict or explai ...

even for highly reactive structures. The structure can also form a

π complex Pi () is a mathematical constant equal to a circle's circumference divided by its diameter. Pi, π or Π may also refer to: Language and typography * Pi (letter), the 17th letter of the Greek alphabet * Pi characters, uncommon characters in t ...

with

lithium Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...

cations, which affects the cycloaddition reactivity. It can even interact strongly enough with

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

species to form a novel type of

metallacycle In organometallic chemistry, a metallacycle is a derivative of a carbocyclic compound wherein a metal has replaced at least one carbon center; this is to some extent similar to heterocycles. Metallacycles appear frequently as reactive intermediates ...

References

{{reflist Reactive intermediates 5 Five-membered rings Hydrocarbons