Cycloheptatriene

Cycloheptatriene

Names
Preferred IUPAC name Cyclohepta-1,3,5-triene
Other names 1,3,5-Cycloheptatriene 1H-[7]Annulene CHT
Identifiers
CAS Number	544-25-2 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:37519 Y
ChemSpider	10534 Y
ECHA InfoCard	100.008.061
InChI InChI=1S/C7H8/c1-2-4-6-7-5-3-1/h1-6H,7H2 Y Key: CHVJITGCYZJHLR-UHFFFAOYSA-N Y InChI=1/C7H8/c1-2-4-6-7-5-3-1/h1-6H,7H2 Key: CHVJITGCYZJHLR-UHFFFAOYAI
SMILES C1=C\C/C=C\C=C1
Properties
Chemical formula	C7H8
Molar mass	92.14 g·mol−1
Density	0.888 g/mL at 25 °C
Melting point	−80 °C (−112 °F; 193 K)
Boiling point	116 °C (241 °F; 389 K)
Solubility in water	Insoluble in water
Hazards
R-phrases (outdated)	R10 R11 R21 R23/24/25 R36/37/38
S-phrases (outdated)	S9 S16 S23 S28A S33 S36/37 S45
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Cycloheptatriene (CHT) 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 methylene bridge (-CH₂-) with respect to the other atoms; however the related tropylium is.

Albert Ladenburg 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 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.

Removal of a hydride ion from the methylene bridge 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 of CHT are known, such as Cr(CO)₃(C₇H₈). Many metal complexes of cycloheptatriene are known. One example is cycloheptatrienemolybdenum tricarbonyl.