Bicyclopropenyl is an organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 and one of several valence isomer

Valence isomer

In organic chemistry, two molecules are valence isomers when they are constitutional isomers that can interconvert through pericyclic reactions.-Benzene:...

s of benzene

Benzene

Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

. The molecule can be described as two coupled cyclopropene

Cyclopropene

Cyclopropene is an organic compound with the formula 34. It is the simplest isolable cycloalkene. It has a triangular structure. Because the ring is highly strained, cyclopropene is both difficult to prepare and interesting to study. Like cyclopropane, the carbon ring of cyclopropene is planar...

 units. The positions of the alkene

Alkene

In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...

 groups can vary and therefore two other isomers are known: bicycloprop-1,2-enyl and bicyclopropen-1-yl.

The synthesis of all three isomers was reported in 1989 By Billups and Haley. The 3,3 isomer was formed in two steps by reaction of 1,4-bis(trimethylsilyl)buta-1,3-diene with methyllithium and dichloromethane

Dichloromethane

Dichloromethane is an organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is miscible with many organic solvents...

, introducing two cyclopropane rings into the molecule. The bis(2-chloro-3-(trimethylsilyl)cyclopropan-1-yl) formed is reacted with TBAF. In this latter reaction fluoride couples to the trimethylsilyl group, in the process forming the double bond and forcing the chlorine atom to leave as chloride. In presence of silver

Silver

Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

 ions bicycloprop-2-enyl rearranges to Dewar benzene

Dewar benzene

Dewar benzene or bicyclo[2.2.0]hexa-2,5-diene is a bicyclic isomer of benzene with the molecular formula C6H6. The compound is named after James Dewar who included this structure in a list of possible C6H6 structures in 1867....

. The compound can also be trapped by cyclopentadiene

Cyclopentadiene

Cyclopentadiene is an organic compound with the formula C5H6. This colorless liquid has a strong and unpleasant odor. At room temperature, this cyclic diene dimerizes over the course of hours to give dicyclopentadiene via a Diels–Alder reaction...

. Above -10 °C it decomposes with polymerization

Polymerization

In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...

.

An X-ray crystal structure has been reported . The bond length

Bond length

- Explanation :Bond length is related to bond order, when more electrons participate in bond formation the bond will get shorter. Bond length is also inversely related to bond strength and the bond dissociation energy, as a stronger bond will be shorter...

 for the central bond is short by 1.503 Ångström

Ångström

The angstrom or ångström, is a unit of length equal to 1/10,000,000,000 of a meter . Its symbol is the Swedish letter Å....

 (150.3 pm).

The other two isomers are increasingly unstable. Bicycloprop-1-enyl can only be detected in trapping experiments.

Properties benzene valence isomers
Compound	Calc. Heat of formation	Calc. Heat of formation
	0 K (KJ/mole)	298 K (KJ/mole)
Benzene Benzene Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....	100.5	82.0
Dewar benzene Dewar benzene Dewar benzene or bicyclo[2.2.0]hexa-2,5-diene is a bicyclic isomer of benzene with the molecular formula C6H6. The compound is named after James Dewar who included this structure in a list of possible C6H6 structures in 1867....	415.5	397.1
Benzvalene Benzvalene Benzvalene is an organic compound and one of several isomers of benzene.. It was synthesised in 1971 by Thomas J. Katz et al.The 1971 synthesis consisted of treating cyclopentadiene with methyllithium in dimethylether and then with dichloromethane and methyllithium in at -45°C. The hydrocarbon in...	397.5	378.1
Prismane Prismane Prismane is a polycyclic hydrocarbon with the formula C6H6. It is an isomer of benzene, more specific: a valence isomer. Prismane is far less stable than benzene. The carbon atoms of the prismane molecule are arranged in the shape of a six-atom triangular prism. Albert Ladenburg proposed this...	567.2	547.0
Bicycloprop-2-enyl	593.6	578.8