.2.2ropellane, formally tricyclo .2.2.0^1,4ctane is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

, a member of the

propellane In organic chemistry, propellane is any member of a class of polycyclic hydrocarbons, whose carbon skeleton consists of three rings of carbon atoms sharing a common carbon–carbon covalent bond. The concept was introduced in 1966 by D. Ginsbu ...

family. It is a

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

with formula C₈H₁₂, or C₂(C₂H₄)₃. Its molecule has three rings with four

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

atoms each, sharing one C–C bond. This compound is unstable (although not as much as .1.1ropellane; however it is less persistent than .1.1ropellane). The bond angles on the shared carbons are considerably strained: three of them are close to 90°, the other three to 120°. The

strain energy In physics, the elastic potential energy gained by a wire during elongation with a tensile (stretching) force is called strain energy. For linearly elastic materials, strain energy is: : U = \frac 1 2 V \sigma \epsilon = \frac 1 2 V E \epsilon ...

is estimated to be 93 kcal/mol (390 kJ/mol).

Synthesis

.2.2ropellane was first synthesized in 1973 by the group of

Philip Eaton Philip E. Eaton (born 1936) is a Professor Emeritus of Chemistry at the University of Chicago. He and his fellow researchers were the first to synthesize the "impossible" cubane molecule in 1964.P. Eaton and T. W. Cole, The Cubane System, J. Am. ...

(who had earlier obtained

cubane Cubane () is a synthetic hydrocarbon compound that consists of eight carbon atoms arranged at the corners of a cube, with one hydrogen atom attached to each carbon atom. A solid crystalline substance, cubane is one of the Platonic hydrocarbons an ...

), according to the following scheme: : 222propellaneSynthesis

The synthesis begins with

photochemical Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible light (400–7 ...

+2 ycloaddition of

ethene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds). Ethylene i ...

on the

cyclohexene Cyclohexene is a hydrocarbon with the formula C6H10. This cycloalkene is a colorless liquid with a sharp smell. It is an intermediate in various industrial processes. Cyclohexene is not very stable upon long term storage with exposure to light a ...

derivative 1 to produce the bicyclic compound 2, followed by

elimination reaction An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one- or two-step mechanism. The one-step mechanism is known as the E2 reaction, and the two-step mechanism is known as the E1 r ...

with potassium ''t''-butoxide of acetic acid to cyclobutene 3, followed by another cycloaddition with ethylene to 4. This compound is converted to the diazo ketone 5 by deprotonation (using acetic acid and

sodium methoxide Sodium methoxide is the simplest sodium alkoxide. With the formula , it is a white solid, which is formed by the deprotonation of methanol. Itis a widely used reagent in industry and the laboratory. It is also a dangerously caustic base. P ...

) and reaction with

tosyl azide Tosyl azide is a reagent used in organic synthesis. Uses Tosyl azide is used for the introduction of azide and diazo functional groups. It is also used as a nitrene source and as a substrate for +2cycloaddition reactions. Preparation Tosy ...

. The ketone then undergoes

Wolff rearrangement The Wolff rearrangement is a reaction in organic chemistry in which an α-diazocarbonyl compound is converted into a ketene by loss of dinitrogen with accompanying 1,2-rearrangement. The Wolff rearrangement yields a ketene as an intermediate produ ...

ketene In organic chemistry, a ketene is an organic compound of the form , where R and R' are two arbitrary monovalent chemical groups (or two separate substitution sites in the same molecule). The name may also refer to the specific compound ethen ...

Ozonolysis In organic chemistry, ozonolysis is an organic reaction where the unsaturated bonds of alkenes (), alkynes (), or azo compounds () are cleaved with ozone (). Alkenes and alkynes form organic compounds in which the multiple carbon–carbon b ...

forms the ketone 7, another diazotation yields the diazo ketone 8, which undergoes Wolff rearrangement again to the ketene 9. Reaction with

dimethylamine Dimethylamine is an organic compound with the formula (CH3)2NH. This secondary amine is a colorless, flammable gas with an ammonia-like odor. Dimethylamine is commonly encountered commercially as a solution in water at concentrations up to aroun ...

affords the .2.2ropellane backbone with a dimethylamide substituent 10. The final product 10 was found to spontaneously isomerize in solution to the monocyclic

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it i ...

11, with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...

of 28 minutes at room temperature.

Derivatives

A highly fluorinated .2.0ropellane was also synthesized by the group of David Lemal.

References

{{DEFAULTSORT:Propellane, 2.2.2 Tricyclic compounds Cyclobutanes Substances discovered in the 1970s

Synthesis

Derivatives

See also

References