Cycloheptatriene

Cycloheptatriene
IUPAC name 1,3,5-cycloheptatriene
Other names CHT
Identifiers
CAS number	544-25-2 Y
ChemSpider	10534 Y
ChEBI	CHEBI:37519 Y
Jmol-3D images	Image 1
SMILES C1=C\C/C=C\C=C1
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
Properties
Molecular formula	C7H8
Molar mass	92.14 g mol−1
Density	0.888 g/mL at 25 °C
Melting point	-80 °C, 193 K, -112 °F
Boiling point	116 °C, 389 K, 241 °F
Solubility in water	Insoluble in water
Hazards
R-phrases	R10 R11 R21 R23/24/25 R36/37/38
S-phrases	S9 S16 S23 S28A S33 S36/37 S45
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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 CH₂ group with respect to the other atoms.

Synthesis

Albert Ladenburg first generated cycloheptatriene in 1881 by the decomposition of tropine.^[1][2] 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.^[3]

Cycloheptatriene can be obtained in the laboratory by photochemical reaction of benzene with diazomethane or the pyrolysis of the adduct of cyclohexene and dichlorocarbene.^[4] 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.^[5][6]

Reactions

Removal of a hydride 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.^[7] CHT behaves as a diene in Diels–Alder reactions. Many metal complexes are known of CHT, such as Cr(CO)₃(C₇H₈). ^[8]

Cyclooctatetraene and cycloheptatriene are used as a triplet quencher for rhodamine 6G dye lasers.^[9][10]

See also

• Cyclopentadiene
• Cyclooctatetraene
• Benzene

References

1. ^ A. Ladenburg (1883). "Die Constitution des Atropins". Justus Liebig's Annalen der Chemie 217 (1): 74–149. doi:10.1002/jlac.18832170107. 
2. ^ A. Ladenburg (1881). "Die Zerlegung des Tropines". Berichte der Deutschen chemischen Gesellschaft 14 (2): 2126–2131. doi:10.1002/cber.188101402127. http://gallica.bnf.fr/ark:/12148/bpt6k906939/f537.chemindefer. 
3. ^ R. Willstätter (1901). "Synthesen in der Tropingruppe. I. Synthese des Tropilidens". Justus Liebig's Annalen der Chemie 317 (2): 204–265. doi:10.1002/jlac.19013170206. 
4. ^ H.E. Winberg (1959). "Synthesis of Cycloheptatriene". Journal of Organic Chemistry 24 (2): 264–265. doi:10.1021/jo01084a635. 
5. ^ Buchner, et al., Ber., 18, 2377 (1885);
6. ^ For a variation: Studies on the Polymethylbenzenes. IX. Addition of Ethyl Diazoacetate to Durene Lee Irvin Smith, Pliny O. Tawney J. Am. Chem. Soc.; 1934; 56(10); 2167-2169. doi:10.1021/ja01325a054
7. ^ Conrow, K. (1973). "Tropylium Fluoroborate". Organic Syntheses, Collected Volume 5,: 1138. http://www.orgsyn.org/orgsyn/pdfs/CV5P1138.pdf. 
8. ^ James H. Rigby, Kevin R. Fales (2004), "7α-ACETOXY-(1Hβ, 6Hβ)-BICYCLO[4.4.1UNDECA-2,4,8-TRIENE VIA CHROMIUM-MEDIATED HIGHER ORDER CYCLOADDITION"], Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV10P0001 ; Coll. Vol. 10: 1 
9. ^ Tomi Nath Das, K. Indira Priyadarsini (1994). "Triplet of Cyclooctatetraene : Reactivity and Properties". Journal of Chemical Society Faraday Transaction 90 (7): 963–968. doi:10.1039/ft9949000963. 
10. ^ R. Pappalardo, H. Samelson, and A. Lempicki (1970). "Long Pulse Laser Emission From Rhodamine 6G Using Cyclooctatetraene". Applied Physics Letters 16 (7): 267–269. doi:10.1063/1.1653190. 

External links