Quadricyclane

Quadricyclane is a strained, multi-cyclic hydrocarbon with potential uses as an additive for rocket propellants as well in solar energy conversion. These uses are limited, however, by the molecule's decomposition at relatively low temperatures (less than 400 °C).

Quadricyclane
Names
IUPAC name
tetracyclo[3.2.0.02,7.04,6]heptane
Other names
quadricyclo[2.2.1.02,6.03.5]heptane, tetracyclo[2.2.1.02,6.03.5]heptane
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.005.450
UNII
Properties
C7H8
Molar mass 92.14 g/mol
Density 0.982 g/cm3
Melting point −44 °C (−47 °F; 229 K)
Boiling point 108 °C (226 °F; 381 K) at 987 hPa
Insoluble
Hazards
R-phrases (outdated) R11 R23
S-phrases (outdated) S16 S29 S33 S45
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

Structure and properties

Quadricyclane is a highly strained molecule (78.7 kcal/mol). Isomerization of quadricyclane proceeds slowly at low temperatures without the use of a catalyst.[1] Because of quadricyclane’s strained structure and thermal stability, it has been studied extensively.

In the presence of a catalyst norbornadiene is converted into quadricyclane via ~300nm UV radiation .[2] When converted back to norbornadiene via irradiation, quadryicyclane’s ring strain energy is liberated in the form of heat (ΔH = −89 kJ/mol). This reaction has been proposed to store solar energy.[3][4] However, the absorption edge of light does not extend past 300 nm whereas most solar radiation has wavelengths longer than 400 nm. Quadricyclane’s relative stability and high energy content have also given rise to its use as a propellant additive or fuel. However, quadricyclane undergoes thermal decomposition at relatively low temperatures (less than 400 °C). This property limits its applications, as propulsion systems may operate at temperatures exceeding 500 °C.[5]

Preparation

Quadricyclane is produced by the irradiation of norbornadiene (bicyclo[2.2.1]hepta-2,5-diene) in the presence of Michler's ketone or ethyl Michler's ketone.[6] Other sensitizers, such as acetone, benzophenone, acetophenone, etc., may be used but with a lesser yield. The yield is higher for freshly distilled norbornadiene, but commercial reagents will suffice.[7]

Reactions

Quadricyclane readily reacts with acetic acid to give a mixture of nortricyclyl acetate and exo-norbornyl acetate.[1] Quadricyclane also reacts with many dienophiles to form 1:1 adducts.[7]

Notes
  1. Petrov, V. A; Vasil’ev, N. V. “Synthetic Chemistry of Quadricyclane.” Current Organic Synthesis 3 (2006): 215–259
  2. Kalsi, P S (2000). Organic Reactions And Their Mechanisms. New Age International. p. 366. ISBN 978-81-224-1268-0.
  3. Dubonosov, A. D; Bren, V. A; Chernoivanov, V. A. “Norbornadiene – quadricyclane as an abiotic system for the storage of solar energy.” Russian Chemical Reviews 71 (2002): 917–927
  4. Philippopoulos, Constantine; Economou, Dimitrios; Economou, Constantine; Marangozis, John (1983). "Norbornadiene-quadricyclane system in the photochemical conversion and storage of solar energy". Industrial & Engineering Chemistry Product Research and Development. 22 (4): 627. doi:10.1021/i300012a021.
  5. Striebich, R; Lawrence, J (2003). "Thermal decomposition of high-energy density materials at high pressure and temperature". Journal of Analytical and Applied Pyrolysis. 70 (2): 339. doi:10.1016/S0165-2370(02)00181-X.
  6. Cahill, P; Steppel, R. Process of quadricyclane production. U.S. Patent 10,661,194 filed September 12, 2003, and issued March 18, 2004
  7. Smith, Claiborune D. (1988). "Quadricyclane". Organic Syntheses.; Collective Volume, 6, p. 962
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