Benzocyclobutene

Benzocyclobutene
IUPAC name Benzocyclobutene
Other names BCB
Identifiers
CAS number	694-87-1 Y
PubChem	24850072
ChemSpider	62868 N
Jmol-3D images	Image 1
SMILES C12=CC=CC=C1CC2
InChI InChI=1S/C8H8/c1-2-4-8-6-5-7(8)3-1/h1-4H,5-6H2 N Key: UMIVXZPTRXBADB-UHFFFAOYSA-N N InChI=1/C8H8/c1-2-4-8-6-5-7(8)3-1/h1-4H,5-6H2 Key: UMIVXZPTRXBADB-UHFFFAOYAR
Properties
Molecular formula	C8H8
Molar mass	104.15 g mol−1
Density	0.957 g/cm3
Boiling point	150 °C; 302 °F; 423 K
Refractive index (nD)	1.541
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Benzocyclobutene (BCB) is a benzene ring fused to a cyclobutane ring. It has chemical formula C₈H₈.^[1]

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-K dielectrics, or even intracortical neural implants.

Pharmaceuticals

The Benzocyclobutene moiety has also appeared in a number of drug molecules. As an example, the amphetamine derived compound appears in the following patent:^[2]

Also see S33005 and the benzocyclobutene analog of 2-cb was prepared by Nichols et al.^[3]

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 favoured.

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.^[4]

See also

• Benzocyclopropene
• Benzocyclobutadiene
• Xylylene

References