4-Vinylbenzocyclobutene
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Product Description
4-Vinylbenzocyclobutene (C₁₀H₁₀) is a bicyclic aromatic olefin in which a benzene ring is fused to a cyclobutene ring and carries a vinyl substituent; IUPAC names such as 3-ethenylbicyclo[4.2.0]octa-1(6),2,4-triene and the common synonym 3-vinylbenzocyclobutene both describe the same rigid framework that combines the π-electron richness of an aryl system with the strain and reactivity of a four-membered ring and an exocyclic double bond. This combination of low dielectric character, thermal stability, and facile polymerization makes the molecule a valued building block for advanced photoresists and high-performance low-k resins in micro- and opto-electronic applications.
Other Information
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Identifiers:
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InChIKey: DTGDMPJDZKDHEP-UHFFFAOYSA-N
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SMILES: C=CC1=CC2=C(CC2)C=C1
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Nikkaji Number: J641.013H
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Synthesis and Production
4-Vinylbenzocyclobutene can be synthesized through several methods:
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Classic Diels-Alder Route: This multi-step process begins with α-bromo-o-xylene. It involves reactions with diethyl malonate, followed by hydrolysis, decarboxylation, and dehydrogenation to form the benzocyclobutene core. The vinyl group is then introduced via a Wittig reaction on 4-bromomethyl-benzocyclobutene, yielding the final product (~50-60% yield).
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Flash Vacuum Pyrolysis (FVP): This method uses a 1,4-divinylbenzene isomer as a precursor. Subjecting it to high temperatures (600–800 °C) induces an electrocyclization reaction that forms the benzocyclobutene core with the pendant vinyl group intact.
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Modern Pd-Catalyzed Coupling: A more efficient route involves a Stille coupling reaction. 4-Iodo-benzocyclobutene is reacted with vinyltributyltin using a Pd(PPh₃)₄ catalyst in toluene at ~100 °C, providing the product in high yields (>80%).
Uses and Applications
The primary application of 4-Vinylbenzocyclobutene is as a monomer in the production of high-performance polymers and materials, leveraging its dual reactivity.
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High-Performance Polymers and Thermosets: It is a key monomer for benzocyclobutene (BCB)-vinyl resins (e.g., commercial products like Cyclotene™). Upon heating, the compound undergoes two simultaneous reactions: the vinyl group polymerizes, and the strained BCB ring opens to form a reactive *o*-quinodimethane intermediate, which cross-links via Diels-Alder reactions. This creates a dense, three-dimensional polymer network with exceptional properties.
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Microelectronics: The resulting cross-linked polymers exhibit a low dielectric constant (κ ~2.6), high thermal stability, and low moisture absorption, making them ideal for use as dielectric layers, interlayer insulators, and encapsulants in semiconductor devices and wafer-level packaging.
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Aerospace and Composites: These polymers are used in adhesives and composite matrices for aerospace applications due to their high glass transition temperature (T_g > 300 °C) and excellent mechanical properties.
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Photolithography and Specialty Polymers: Photo-active versions are used in photolithography. It has also been studied for use in dental composites and for functionalizing carbon nanotubes to enhance the mechanical properties of fibers.
Properties and Characteristics
| Property | Value/Description |
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| Molecular Formula | C₁₀H₁₀ |
| IUPAC Name | 3-ethenylbicyclo[4.2.0]octa-1(6),2,4-triene |
| CAS Number | 99717-87-0 |
| EC Number | 663-548-5 |
| Molecular Weight | 130.19 g/mol |
| XLogP3 | 2.1 |
| Hydrogen Bond Donor Count | 0 |
| Hydrogen Bond Acceptor Count | 0 |
| Rotatable Bond Count | 1 |
| Topological Polar Surface Area | 0 Ų |
| Heavy Atom Count | 10 |
| Complexity | 137 |
| Appearance | Colorless to pale yellow liquid |
| Key Reactivity | The strained cyclobutene ring undergoes thermal ring-opening at ~200°C to form a reactive *o*-quinodimethane diene, which readily participates in Diels-Alder cycloadditions and cross-linking. |
Safety and Handling
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Hazard Classification (GHS):
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Signal Word: Warning
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Hazard Statement: H302 (Harmful if swallowed).
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Pictogram: GHS07 (Exclamation mark)
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Precautionary Statements: P264, P270, P301+P317, P330, P501 (Recommendations include washing hands thoroughly after handling, not eating/drinking/smoking when using, and seeking medical attention if swallowed).
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Handling and Storage: It is a flammable liquid and can be an irritant to skin and eyes. The vinyl group is prone to radical polymerization, so an inhibitor like BHT is typically added for stability. It should be stored in a cool, dark place under an inert atmosphere (e.g., nitrogen) to prevent polymerization and degradation, with a typical shelf life of 6–12 months.