Benzocyclobutene
Chemical compound
From Wikipedia, the free encyclopedia
Benzocyclobutene (BCB) is a benzene ring fused to a cyclobutane ring. It has chemical formula C8H8.[1]
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| Names | |
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| Preferred IUPAC name
Bicyclo[4.2.0]octa-1,3,5-triene | |
| Other names
Benzocyclobutane BCB Benzocyclobutene (not in accordance with IUPAC nomenclature) | |
| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.161.355 |
PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| C8H8 | |
| Molar mass | 104.152 g·mol−1 |
| Density | 0.957 g/cm3 |
| Boiling point | 150 °C (302 °F; 423 K) |
Refractive index (nD) |
1.541 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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BCB is frequently used to create photosensitive polymers. BCB-based polymer dielectrics may be spun on or applied to various substrates for use in Micro Electro-Mechanical Systems (MEMS) and microelectronics processing. Applications include wafer bonding, optical interconnects, low-κ dielectrics, or even intracortical neural implants.
Reactions
Benzocyclobutene is a strained system which, upon heating to approximately 180 °C, causes the cyclobutene to undergo a conrotatory ring-opening reaction, forming o-xylylene. Since this process destroys the aromaticity of the benzene ring, the reverse reaction is highly favored.
o-Xylylenes generated in this way have been used prolifically in cycloaddition reactions, which restore the aromaticity to the benzene ring, while forming a new annulated species.[2]
Derivatives
Cyclized phenethylamine psychedelic drugs containing the benzocyclobutene ring system, including TCB-2, tomscaline, bromotomscaline, and 2CBCB-NBOMe (NBOMe-TCB-2), have been described.[3] A benzocyclobutene-derived amphetamine has been patented as well,[4] and a benzocyclobutene containing designer drug, the substituted cathinone derivative 3,4-EtPV, has been sold in Europe.[5] The benzocyclobutene derivative 2C-G-2 has also been claimed in a patent as an antiinflammatory,[6] but no synthesis or activity data is provided so it is unclear if it has actually been made.
The benzocyclobutene moiety also appears in the FDA approved medication ivabradine.