Cyclobutadiene is an organic compound, a four-membered cycle with alternated (alternating) double bonds . Its gross formula is C 4 H 4 . In the free state, cyclobutadiene is extremely unstable, and even at low temperatures it dimers very quickly. The cyclobutadiene molecule is an elongated rectangle. Although this compound is capable of forming a closed π-system, according to the Hückel rule it is , since it contains 4 n π-electrons (in this case n = 1). This means that with the formation of a conjugated π-system, the total energy of the molecule will increase. Indeed, if we draw for cyclobutadiene, we can easily see that the conjugated system will be a . It should be noted that in order for this system to become aromatic, one must either introduce two electrons into it or take them away, with the formation of a dianion or dication, respectively. The resulting compounds are much more stable than cyclobutadiene and can be isolated.
| Cyclobutadiene | |
|---|---|
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| General | |
| Systematic name | cyclobuta-1,3-diene |
| Chem. formula | C 4 H 4 |
| Physical properties | |
| Molar mass | 52.07 g / mol |
| Classification | |
| Reg. CAS number | 1120-53-2 |
| PubChem | |
| Smiles | |
| Inchi | |
| Chebi | |
| ChemSpider | |
Getting
After many unsuccessful attempts, cyclobutadiene was first synthesized in 1965 by Rowland Pettit, a student at the University of Texas by acting on cyclobutadiene iron tricarbonyl C 4 H 4 Fe (CO) 3 with an oxidizing agent such as (NH 4 ) 2 Ce (NO 3 ) 6 , but could not isolate it in its free form, since it dimerizes.
To date, it has been shown that cyclobutadiene can be synthesized in an argon matrix , where this compound was studied in detail by IR and EPR spectroscopy, and its structure and the fact that it is a biradical are shown. However, even with a slight increase in temperature (up to −150 ° C), cyclobutadiene slowly dimerizes. Substituted cyclobutadienes are substantially more stable. In particular, tetra- tert- butylcyclobutadiene and tetra-trimethylsilylcyclobutadiene are stable at room temperature due to bulky substituents preventing dimerization.
See also
- Cyclobutane
- Cyclobutene
- Butadiene