Cycloheptane

Summary

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]

Cycloheptane
Skeletal formula
Ball-and-stick model
Names
Preferred IUPAC name
Cycloheptane
Identifiers
  • 291-64-5 checkY
3D model (JSmol)
  • Interactive image
ChEMBL
  • ChEMBL453194 checkY
ChemSpider
  • 8908 checkY
ECHA InfoCard 100.005.483 Edit this at Wikidata
EC Number
  • 206-030-2
  • 9265
UNII
  • VTZ53P34JA checkY
UN number 2241
  • DTXSID0074269 Edit this at Wikidata
  • InChI=1S/C7H14/c1-2-4-6-7-5-3-1/h1-7H2 checkY
    Key: DMEGYFMYUHOHGS-UHFFFAOYSA-N checkY
  • InChI=1/C7H14/c1-2-4-6-7-5-3-1/h1-7H2
    Key: DMEGYFMYUHOHGS-UHFFFAOYAF
  • C1CCCCCC1
Properties
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)
negligible
Solubility very soluble in ethanol, ether
soluble in benzene, chloroform
log P 4.0
1.4436
Hazards
GHS labelling:
GHS02: FlammableGHS08: Health hazard
Danger
H225, H304, H412
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).
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Infobox references

ConformationsEdit

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]

ReferencesEdit

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