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Cyclononatetraene is an
Cyclononatetraenyl cation is an 8π system. Its intermediacy is implicated in the solvolysis of 1. The facile solvolysis of 1 suggests that the cation is stabilized. Computation and experimental evidence suggest that C9H9+ is a rare example of a ground state species that exhibits
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...
with the formula C9H10. It was first prepared in 1969 by protonation of the corresponding aromatic anion (described below). It is unstable and isomerizes with a half-life of 50 minutes at room temperature to 3a,7a-dihydro-1''H-''indene via a thermal 6π disrotatory electrocyclic ring closing. Upon exposure to ultraviolet light, it undergoes a photochemical 8π electrocyclic ring closing to give bicyclo .1.0ona-2,4,6-triene.
Cyclononatetraenyl anion
Cyclononatetraenyl anion is a 10π aromatic system. Two isomers of the cyclononatetraenyl anion are known: the ''trans'',''cis'',''cis'',''cis'' isomer (" Pac-Man"-shaped) and the all-''cis'' isomer (a convexenneagon
In geometry, a nonagon () or enneagon () is a nine-sided polygon or 9-gon.
The name ''nonagon'' is a prefix hybrid formation, from Latin (''nonus'', "ninth" + ''gonon''), used equivalently, attested already in the 16th century in French ''nonogo ...
). The former is less stable and isomerizes to the latter upon warming from –40 °C to room temperature.
The all-''cis'' isomer of C9H9− can be prepared by treatment of 9-chlorobicyclo .1.0ona-2,4,6-triene (1) with lithium or potassium metal. Despite the ring strain resulting from having C–C–C bond angles of 140° instead of the ideal 120° for sp2 carbon, this species is believed to be planar and to possess ''D''9h symmetry. The lithium salt was found to be react with cyclopentadiene to give lithium cyclopentadienide, showing that cyclononatetraene is a weaker acid than cyclopentadiene.
Cyclononatetraenyl cation
Cyclononatetraenyl cation is an 8π system. Its intermediacy is implicated in the solvolysis of 1. The facile solvolysis of 1 suggests that the cation is stabilized. Computation and experimental evidence suggest that C9H9+ is a rare example of a ground state species that exhibits Möbius aromaticity
In organic chemistry, Möbius aromaticity is a special type of aromaticity believed to exist in a number of organic molecules. In terms of molecular orbital theory these compounds have in common a monocyclic array of molecular orbitals in which th ...
.''Topology in Chemistry: Designing Möbius Molecules'' Herges, R. Chem. Rev.; (Review); 2006; 106(12); 4820-4842.
See also
* Cyclopentadiene *Cyclooctatetraene
1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as nnulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of ...
* Cycloheptatriene
Cycloheptatriene (CHT) is an organic compound with the formula C7H8. It is a closed ring of seven carbon atoms joined by three double bonds (as the name implies) and four single bonds. This colourless liquid has been of recurring theoretical inter ...
* Azonine
References
{{Cycloalkenes Cycloalkenes Annulenes Non-benzenoid aromatic carbocycles Nine-membered rings