Cycloheptatriene (CHT) is an

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 ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

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 interest in

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...

. It is a ligand in

organometallic chemistry Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...

and a building block in

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

. Cycloheptatriene is not

aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...

, as reflected by the nonplanarity of the

methylene bridge In chemistry, a methylene bridge is part of a molecule with formula . The carbon atom is connected by single bonds to two other distinct atoms in the rest of the molecule. A methylene bridge is often called a methylene group or simply methylene, ...

() with respect to the other atoms; however the related

tropylium cation The tropylium ion or cycloheptatrienyl cation is an aromatic species with a formula of 7H7sup>+. Its name derives from the molecule tropine from which cycloheptatriene (tropylidene) was first synthesized in 1881. Salts of the tropylium cation ...

is, rendering the compound relatively suspectible to

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

Synthesis

Albert Ladenburg first generated cycloheptatriene in 1881 by the decomposition of tropine. The structure was finally proven by the synthesis of

Richard Willstätter Richard Martin Willstätter FRS(For) HFRSE (, 13 August 1872 – 3 August 1942) was a German organic chemist whose study of the structure of plant pigments, chlorophyll included, won him the 1915 Nobel Prize for Chemistry. Life Willstätter wa ...

in 1901. This synthesis started from cycloheptanone and established the seven membered ring structure of the compound. Cycloheptatriene can be obtained in the laboratory by

photochemical reaction Organic photochemistry encompasses organic reactions that are induced by the action of light. The absorption of ultraviolet light by organic molecules often leads to reactions. In the earliest days, sunlight was employed, while in more modern times ...

benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...

with

diazomethane Diazomethane is an organic chemical compound with the formula CH2N2, discovered by German chemist Hans von Pechmann in 1894. It is the simplest diazo compound. In the pure form at room temperature, it is an extremely sensitive explosive yellow ga ...

or the pyrolysis of the adduct of

cyclohexene Cyclohexene is a hydrocarbon with the formula . It is a cycloalkene. At room temperature, cyclohexene is a colorless liquid with a sharp odor. Among its uses, it is an chemical intermediate, intermediate in the commercial synthesis of nylon. Prod ...

and

dichlorocarbene Dichlorocarbene is the reactive intermediate with chemical formula CCl2. Although this chemical species has not been isolated, it is a common intermediate in organic chemistry, being generated from chloroform. This bent diamagnetic molecule rapi ...

. A related classic synthesis for cycloheptatriene derivatives, the Buchner ring enlargement, starts with the reaction of

with

ethyl diazoacetate Ethyl diazoacetate (N=N=CHC(O)OC2H5) is a diazo compound and a reagent in organic chemistry. It was discovered by Theodor Curtius in 1883. The compound can be prepared by reaction of the ethyl ester of glycine with sodium nitrite and sodium aceta ...

to give the corresponding norcaradiene ethyl ester, which then undergoes a thermally-allowed electrocyclic ring expansion to give 1,3,5-cycloheptatriene 7-carboxylic acid ethyl ester. TOC_ACS1996v2

File:Chemical_structure_of_heptalene.png, Heptalene – composed of two fused cycloheptatriene rings. File:Azulene struttura.svg, Azulene – composed of fused

cyclopentadiene Cyclopentadiene is an organic compound with the chemical formula, formula C5H6. It is often abbreviated CpH because the cyclopentadienyl anion is abbreviated Cp−. This colorless liquid has a strong and unpleasant odor. At room temperature, ...

and cycloheptatriene rings. File:Pentaheptafulvalene.png, Sesquifulvalene – composed of linked cyclopentadiene and cycloheptatriene rings. File:Elassovalene.svg, Elassovalene – composed of one cycloheptatriene and two fused cyclopentene rings. File:Tropone.png, Tropone – composed of cycloheptatriene ring and

carbonyl group In organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such as aldehydes ...

. File:Tropolone.png, Tropolone – composed of cycloheptatriene ring,

carbonyl In organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double bond, double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such a ...

and hydroxy groups. File:Gamma-thujaplicin.png, Hinokitiol – composed of cycloheptatriene ring,

isopropyl In organic chemistry, a propyl group is a three-carbon alkyl substituent with chemical formula for the linear form. This substituent form is obtained by removing one hydrogen atom attached to the terminal carbon of propane. A propyl substituent ...

and hydroxy groups (

cycloheptatrienolone).

Reactions

Removal of a

hydride In chemistry, a hydride is formally the anion of hydrogen (H−), a hydrogen ion with two electrons. In modern usage, this is typically only used for ionic bonds, but it is sometimes (and has been more frequently in the past) applied to all che ...

ion from the

gives the planar and aromatic cycloheptatriene cation, also called the tropylium ion. A practical route to this cation employs PCl₅ as the oxidant. CHT behaves as a diene in

Diels–Alder reaction In organic chemistry, the Diels–Alder reaction is a chemical reaction between a Conjugated system, conjugated diene and a substituted alkene, commonly termed the Diels–Alder reaction#The dienophile, dienophile, to form a substituted cyclohexe ...

s, for example with

maleic anhydride Maleic anhydride is an organic compound with the formula . It is the acid anhydride of maleic acid. It is a colorless or white solid with an acrid odor. It is produced industrially on a large scale for applications in coatings and polymers. Str ...

: :

Many

metal complex A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or ...

es of cycloheptatriene are known, including Cr(CO)₃(C₇H₈) and cycloheptatrienemolybdenum tricarbonyl.

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 ...

and cycloheptatriene are used as a triplet quencher for rhodamine 6G

dye laser A dye laser is a laser that uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths, often spanning 50 to 100 n ...

References

{{Annulenes Annulenes Seven-membered rings

Synthesis

Reactions

See also

References