Cycloheptane

Cycloheptane
Names
	Preferred IUPAC name Cycloheptane
Identifiers
CAS Number	291-64-5 ;
3D model (JSmol)	Interactive image;
ChEMBL	ChEMBL453194 ;
ChemSpider	8908 ;
ECHA InfoCard	100.005.483
EC Number	206-030-2;
PubChem CID	9265;
UNII	VTZ53P34JA ;
UN number	2241
CompTox Dashboard (EPA)	DTXSID0074269 ;
	InChI InChI=1S/C7H14/c1-2-4-6-7-5-3-1/h1-7H2 Key: DMEGYFMYUHOHGS-UHFFFAOYSA-N ; InChI=1/C7H14/c1-2-4-6-7-5-3-1/h1-7H2 Key: DMEGYFMYUHOHGS-UHFFFAOYAF;
	SMILES C1CCCCCC1;
Properties
Chemical formula	C7H14
Molar mass	98.189 g·mol−1
Appearance	colorless oily liquid
Density	0.8110 g/cm3
Melting point	−12 °C (10 °F; 261 K)
Boiling point	118.4 °C (245.1 °F; 391.5 K)
Solubility in water	negligible
Solubility	very soluble in ethanol, ether ; soluble in benzene, chloroform
log P	4.0
Refractive index (nD)	1.4436
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H304, H412
Precautionary statements	P210, P233, P240, P241, P242, P243, P273, P280, P301+P310, P303+P361+P353, P331, P370+P378, P403+P235, P405, P501
NFPA 704 (fire diamond)	1 3 0
Flash point	6 °C (43 °F; 279 K)
Related compounds
Related cycloalkanes	Cyclohexane Cyclooctane
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Cycloheptane is a cycloalkane with the molecular formula C₇H₁₄. Cycloheptane is used as a nonpolar solvent for the chemical industry and as an intermediate in the manufacture of chemicals and pharmaceutical drugs. It may be derived by Clemmensen reduction from cycloheptanone. Cycloheptane vapour is irritating to the eyes and may cause respiratory depression if inhaled in large quantity.^[1]

Conformations

Cycloheptane is not a flat molecule, because that would give C-C-C bond angles much greater than the tetrahedral angle of around 109.5°. Instead it is puckered and three-dimensional. One can ask the question of what conformations would have the same angle everywhere (near 109.5°) and all bond lengths equal. If we think of an open chain of seven bonds, there are five dihedral angles that can be chosen, for the sequences (1,2,3,4), (2,3,4,5), and so on. The last bond though should end where the first began, and should form the correct angle with the first bond. This imposes four constraints, but we have five dihedral angles to play with, so there is one degree of freedom. It turns out that there are two continua of solutions. One is a circular series of fourteen "boat" conformations interspersed with "twist-boat" conformations, and the other is a circular series of fourteen "chair" conformations interspersed with "twist-chair" conformations. The boat and chair conformations have mirror symmetry, while the twist-boat and twist-chair have two-fold rotational symmetry. Conformations between boat and twist-boat or between chair and twist-chair have no symmetry. The passage along the continuum boat→twist-boat→boat→twist-boat→boat constitutes a pseudorotation, as does chair→twist-chair→chair→twist-chair→chair.

Actually in cycloheptane the conformations will not have exactly equal bond angles and lengths everywhere, because they do not have a seven-fold rotation or improper rotation. This contrasts with the chair form of cyclohexane in which all the bond angles and lengths are equal due to symmetry.

Below are depicted the boat and chair conformations.^[2]

Boat
Chair

References

^ Mackay, Donald (2006). Handbook of Physical-chemical Properties and Environmental Fate for Organic Chemicals. CRC Press. ISBN 978-1566706872.
^ Bocian, D. F.; Pickett, H. M.; Rounds, T. C.; Strauss, H. L. (1975). "Conformations of cycloheptane". Journal of the American Chemical Society. 97 (4): 687–695. doi:10.1021/ja00837a001. ISSN 0002-7863.

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[hpcp-1] Mackay, Donald (2006). Handbook of Physical-chemical Properties and Environmental Fate for Organic Chemicals. CRC Press. ISBN 978-1566706872.

[:0-2] Bocian, D. F.; Pickett, H. M.; Rounds, T. C.; Strauss, H. L. (1975). "Conformations of cycloheptane". Journal of the American Chemical Society. 97 (4): 687–695. doi:10.1021/ja00837a001. ISSN 0002-7863.

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