Cycloheptatriene
Encyclopedia
Cycloheptatriene is an organic compound
with the formula
C7H8. This colourless liquid has been of recurring theoretical interest in organic chemistry
. It is a ligand in organometallic chemistry
and as a building block in organic synthesis
. Cycloheptatriene is not aromatic, as reflected by the nonplanarity of the CH2
group with respect to the other atoms.
first generated cycloheptatriene in 1881 by the decomposition of tropine
. The structure was finally proven by the synthesis of Richard Willstätter
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 of benzene
with diazomethane
or the pyrolysis of the adduct of cyclohexene
and dichlorocarbene
. A related classic synthesis for a cycloheptatriene derivatives, the "Buchner ring enlargement, starts with the reaction of benzene
with ethyl diazoacetate
to give the corresponding norcaradiene carboxylic acid
, which at high temperatures rearranges with ring expansion
to the cycloheptatriene carboxylic acid ethyl ester.
ion from the methylene
group 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 reactions. Many metal complexes are known of CHT, such as Cr(CO)3(C7H8).
Cyclooctatetraene
and cycloheptatriene are used as a triplet quencher for rhodamine 6G
dye laser
s.
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...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
C7H8. This colourless liquid has been of recurring theoretical interest in organic chemistry
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
. It is a ligand in organometallic chemistry
Organometallic chemistry
Organometallic chemistry is the study of chemical compounds containing bonds between carbon and a metal. Since many compounds without such bonds are chemically similar, an alternative may be compounds containing metal-element bonds of a largely covalent character...
and as a building block in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
. Cycloheptatriene is not aromatic, as reflected by the nonplanarity of the CH2
Methylene
Methylene is a chemical species in which a carbon atom is bonded to two hydrogen atoms. Three different possibilities present themselves:* the -CH2- substituent group: e.g., dichloromethane ....
group with respect to the other atoms.
Synthesis
Albert LadenburgAlbert Ladenburg
Albert Ladenburg was a German chemist.-Biography:Ladenburg was a member of a well known Jewish family in Mannheim. He was educated at a Realgymnasium at Mannheim and then, after the age of 15, at the technical school of Karlsruhe, where he studied mathematics and modern languages...
first generated cycloheptatriene in 1881 by the decomposition of tropine
Tropine
Tropine is a derivative of tropane containing a hydroxyl group at third carbon. It is also called 3-tropanol.Benzatropine and etybenzatropine are derivatives of tropine. It is also a building block of atropine, a cholinergic drug prototypical of the muscarinic antagonist class.-External Links:*...
. The structure was finally proven by the synthesis of Richard Willstätter
Richard Willstätter
Richard Martin Willstätter was a German organic chemist whose study of the structure of plant pigments, chlorophyll included, won him the 1915 Nobel Prize for Chemistry. Willstätter invented paper chromatography independently of Mikhail Tsvet.-Biography:Willstätter was born in to a Jewish family...
in 1901. This synthesis started from cycloheptanone
Cycloheptanone
Cycloheptanone, 6CO, is a cyclic ketone also referred to as suberone. It is a colourless volatile liquid. Cycloheptanone is used as a precursor for the synthesis of pharmaceuticals.- Synthesis :...
and established the seven membered ring structure of the compound.
Cycloheptatriene can be obtained in the laboratory by photochemical reaction of benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
with diazomethane
Diazomethane
Diazomethane is the chemical compound CH2N2. It is the simplest of diazo compounds. In the pure form at room temperature, it is a extremely sensitive explosive yellow gas, thus it is almost universally used as a solution in diethyl ether...
or the pyrolysis of the adduct of 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...
and dichlorocarbene
Dichlorocarbene
Dichlorocarbene is a carbene commonly encountered in organic chemistry. This reactive intermediate with chemical formula CCl2 is easily available by reaction of chloroform and a base such as potassium t-butoxide or sodium hydroxide dissolved in water...
. A related classic synthesis for a cycloheptatriene derivatives, the "Buchner ring enlargement, starts with the reaction of benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
with ethyl diazoacetate
Ethyl diazoacetate
Ethyl diazoacetate 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 acetate in water....
to give the corresponding norcaradiene carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
, which at high temperatures rearranges with ring expansion
Ring expansion reaction
In chemistry, ring expansion and ring contraction are chemical reactions that increase or decrease, respectively, the number of atoms in a ring of a cyclic compound.- Ring expansion reactions :Examples of ring expansion reactions are:...
to the cycloheptatriene carboxylic acid ethyl ester.
Reactions
Removal of a hydrideHydride
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
ion from the methylene
Methylene
Methylene is a chemical species in which a carbon atom is bonded to two hydrogen atoms. Three different possibilities present themselves:* the -CH2- substituent group: e.g., dichloromethane ....
group 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 reactions. Many metal complexes are known of CHT, such as Cr(CO)3(C7H8).
Cyclooctatetraene
Cyclooctatetraene
1,3,5,7-Cyclooctatetraene is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as [8]annulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature...
and cycloheptatriene are used as a triplet quencher for rhodamine 6G
Rhodamine 6G
Rhodamine 6G is a chemical compound and a dye. It is often used as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with instruments called fluorometers...
dye laser
Dye laser
A dye laser is a laser which 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. The wide bandwidth makes them particularly suitable for tunable lasers and...
s.