Bicyclo .1.0utane is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula C₄H₆. It is a

bicyclic molecule A bicyclic molecule () is a molecule that features two joined rings. Bicyclic structures occur widely, for example in many biologically important molecules like α-thujene and camphor. A bicyclic compound can be carbocyclic (all of the ring ...

consisting of two '' cis''-fused

cyclopropane Cyclopropane is the cycloalkane with the molecular formula (CH2)3, consisting of three methylene groups (CH2) linked to each other to form a triangular ring. The small size of the ring creates substantial ring strain in the structure. Cyclopropane ...

rings, and is a colorless and easily condensed gas. Bicyclobutane is noted for being one of the most strained compounds that is isolatable on a large scale — its strain energy is estimated at 63.9 kcal mol⁻¹. It is a nonplanar molecule, with a dihedral angle between the two cyclopropane rings of 123°. The first reported bicyclobutane was the ethyl carboxylate derivative, C₄H₅CO₂Et, which was prepared by

dehydrohalogenation In chemistry, dehydrohalogenation is an elimination reaction which removes a hydrogen halide from a substrate (chemistry), substrate. The reaction is usually associated with the synthesis of alkenes, but it has wider applications. Dehydrohalogen ...

the corresponding bromo

cyclobutane Cyclobutane is a cycloalkane and organic compound with the formula (CH2)4. Cyclobutane is a colourless gas and is commercially available as a liquefied gas. Derivatives of cyclobutane are called cyclobutanes. Cyclobutane itself is of no commerc ...

carboxylate ester with

sodium hydride Sodium hydride is the chemical compound with the empirical formula Na H. This alkali metal hydride is primarily used as a strong yet combustible base in organic synthesis. NaH is a saline (salt-like) hydride, composed of Na+ and H− ions, in co ...

. The parent hydrocarbon was prepared from 1-bromo-3-chlorocyclobutane by conversion of the bromocyclobutanecarboxylate ester, followed by intramolecular

Wurtz coupling In organic chemistry, the Wurtz reaction, named after Charles Adolphe Wurtz, is a coupling reaction in which two alkyl halides are treated with sodium metal to form a higher alkane. : 2 R−X + 2 Na → R−R + 2 NaX The reaction is of little val ...

using molten

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

. The intermediate 1-bromo-3-chlorocyclobutane can also be prepared via a modified

Hunsdiecker reaction The Hunsdiecker reaction (also called the Borodin reaction or the Hunsdiecker–Borodin reaction) is a name reaction in organic chemistry whereby silver salts of carboxylic acids react with a halogen to produce an organic halide. It is an ex ...

from 3-chlorocyclobutanecarboxylic acid using

mercuric oxide Mercury(II) oxide, also called mercuric oxide or simply mercury oxide, is the inorganic compound with the formula Hg O. It has a red or orange color. Mercury(II) oxide is a solid at room temperature and pressure. The mineral form montroydite is ...

and

bromine Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...

: :

A synthetic approach to bicyclobutane derivatives involves ring closure of a suitably substituted 2-bromo-1-(chloromethyl)cyclopropane with magnesium in

THF Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water-miscible organic liquid with low viscosity. It is ma ...

. Substituted bicyclo .1.0utanes can also be prepared from the reaction of iodo-bicyclo .1.1entanes with amines, thiols, and sulfinate salts. Bicyclo .1.0utanes are explored in medicinal chemistry as covalent reactive groups. : SchemeBCBs

Stereochemical evidence indicates that bicyclobutane undergoes

thermolysis Thermal decomposition, or thermolysis, is a chemical decomposition of a substance caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic ...

to form

1,3-butadiene 1,3-Butadiene () is the organic compound with the formula CH2=CH-CH=CH2. It is a colorless gas that is easily condensed to a liquid. It is important industrially as a precursor to synthetic rubber. The molecule can be viewed as the union of two ...

with an

activation energy In the Arrhenius model of reaction rates, activation energy is the minimum amount of energy that must be available to reactants for a chemical reaction to occur. The activation energy (''E''a) of a reaction is measured in kilojoules per mole (k ...

of 41 kcal mol⁻¹ via a

concerted In chemistry, a concerted reaction is a chemical reaction in which all bond breaking and bond making occurs in a single step. Reactive intermediates or other unstable high energy intermediates are not involved. Concerted reaction rate The ...

pericyclic In organic chemistry, a pericyclic reaction is the type of organic reaction wherein the transition state of the molecule has a cyclic geometry, the reaction progresses in a concerted fashion, and the bond orbitals involved in the reaction overl ...

mechanism (cycloelimination, �2s+σ2a.

Biological synthesis

Linolenic acid Linolenic acid is a type of naturally-occurring fatty acid. It can refer to either of two octadecatrienoic acids (i.e. with an 18-carbon chain and three double bonds, which are found in the '' cis'' configuration), or a mixture of the two. Lino ...

can be converted into its bicyclobutane derivative using a

fusion protein Fusion proteins or chimeric (kī-ˈmir-ik) proteins (literally, made of parts from different sources) are proteins created through the joining of two or more genes that originally coded for separate proteins. Translation of this '' fusion gene'' ...

produced by a strain of the cyanobacterium '' Anabaena sphaerica'' (strain PCC 7120). The other group reported a directed evolution approach, whereby engineered heme protein was expressed in ''E. coli'' and optimized for rate and yield of a substituted bicyclobutane derivative.{{Cite journal, last1=Chen, first1=Kai, last2=Huang, first2=Xiongyi, last3=Kan, first3=S. B. Jennifer, last4=Zhang, first4=Ruijie K., last5=Arnold, first5=Frances H., date=6 April 2018, title=Enzymatic construction of highly strained carbocycles, journal=Science, volume=360, issue=6384, pages=71–75, doi=10.1126/science.aar4239, issn=1095-9203, pmc=6104391, pmid=29622650, bibcode=2018Sci...360...71C

References

Cyclopropanes Bicycloalkanes Gases

Biological synthesis

See also

References