Chemical Structure and Physical Properties

1,3-Difluoro-5-vinylbenzene (CAS 72235-20-2, MW 140.13 g/mol, molecular formula C₈H₆F₂) belongs to the class of fluorinated styrene derivatives. The compound features a benzene ring bearing two fluorine atoms at the 1- and 3-positions (meta relationship to each other) and a vinyl (ethenyl) group at the 5-position, giving the molecule a symmetric substitution pattern about the vinyl-bearing carbon.

The two fluorine substituents are strongly electron-withdrawing by induction, reducing electron density on the aromatic ring and influencing the regioselectivity of electrophilic and nucleophilic reactions at the ring. The vinyl group, conjugated with the π-system of the aromatic ring, provides a site for radical, anionic, and transition-metal-catalysed polymerisation or functionalisation reactions.

Key predicted/typical physical properties for compounds in this class include a colourless to pale yellow liquid appearance at room temperature, relatively low molecular weight consistent with moderate volatility, and limited water solubility due to the hydrophobic aromatic core. Researchers should consult the certificate of analysis supplied with SKU D729417 for confirmed purity, appearance, and spectral data.

Synthesis and Availability

1,3-Difluoro-5-vinylbenzene is most commonly accessed via palladium-catalysed cross-coupling reactions, particularly Heck-type or Suzuki–Miyaura couplings starting from 3,5-difluorohalobenzenes (e.g., 3,5-difluorobromobenzene or 3,5-difluoroiodobenzene) and vinyl-boron or vinyl-tin reagents. Alternatively, Wittig-type olefination of 3,5-difluorobenzaldehyde with methylenetriphenylphosphorane provides a metal-free synthetic route.

Another approach involves the vinylation of 1,3-difluorobenzene using directing-group-assisted C–H activation strategies, although selectivity control at the 5-position requires careful optimisation. Dehydrohalogenation of 1-(3,5-difluorophenyl)ethyl halides under basic conditions has also been reported as a preparative option.

Aladdin Scientific offers 1,3-Difluoro-5-vinylbenzene as catalogue reagent SKU D729417, providing researchers with a convenient, quality-controlled commercial source that avoids the need for multistep in-house synthesis. Storage under inert atmosphere at low temperature is recommended to prevent radical-initiated polymerisation of the vinyl group during prolonged storage.

Reactivity and Key Reactions

Radical and Anionic Polymerisation: The styrenic vinyl group of 1,3-Difluoro-5-vinylbenzene undergoes free-radical polymerisation under standard initiator conditions (e.g., AIBN, peroxides) to yield poly(3,5-difluorostyrene), a fluorinated polymer with modified dielectric and thermal properties relative to polystyrene. Controlled radical polymerisation techniques such as RAFT and ATRP can be used to produce well-defined homo- or copolymers.

Transition-Metal-Catalysed Functionalisation: The aryl C–F bonds in 1,3-difluoro-5-vinylbenzene can participate in selective C–F activation with appropriate metal catalysts, providing routes to partially defluorinated or cross-coupled products. The compound can also serve as a Heck coupling partner via its vinyl group.

Diels–Alder Cycloaddition: As an electron-poor dienophile (due to the ring fluorines withdrawing electron density into the ring and slightly reducing vinyl electron density), 1,3-Difluoro-5-vinylbenzene can act as a dienophile in [4+2] cycloadditions with electron-rich dienes, though reactivity is modest compared to strongly activated dienophiles.

Electrophilic Aromatic Substitution: The 1,3-difluoro substitution pattern directs incoming electrophiles preferentially to the 5-position; however, with the vinyl group already occupying the 5-position, further EAS must occur at the 2- or 4-positions, which are electronically deactivated by the fluorines.

Applications in Research and Industry

Pharmaceutical and Medicinal Chemistry: Fluorinated aromatic compounds are widely used in drug discovery because C–F bonds improve metabolic stability, lipophilicity, and membrane permeability of drug candidates. 1,3-Difluoro-5-vinylbenzene serves as a versatile synthetic intermediate: the vinyl group can be oxidised to an aldehyde or carboxylic acid, used in ring-forming reactions, or elaborated via cross-coupling to install diverse pharmacophores onto the 3,5-difluorophenyl scaffold.

Agrochemical Synthesis: Similar metabolic stability advantages make 3,5-difluorophenyl-containing fragments valuable in agrochemical active ingredient design. The compound can function as a building block for the construction of fluorinated herbicides, fungicides, or insecticides.

Functional Polymer and Materials Science: Homo- and co-polymers derived from 1,3-Difluoro-5-vinylbenzene exhibit lower dielectric constants and improved hydrophobicity relative to unfluorinated polystyrene analogues, making them candidates for low-k dielectric materials, fluoropolymer coatings, and membrane applications.

Chemical Biology Probes: The ¹⁹F nucleus has 100% natural abundance and a high gyromagnetic ratio, making fluorine-containing compounds useful as ¹⁹F NMR or ¹⁹F MRI probes. Polymers or small molecules derived from 1,3-Difluoro-5-vinylbenzene can be incorporated into probe architectures for tracking biological processes.

Handling, Safety and Storage

General Handling Precautions: As with all reactive vinyl-containing aromatic compounds, 1,3-Difluoro-5-vinylbenzene should be handled in a well-ventilated fume hood with appropriate personal protective equipment including chemical-resistant gloves, safety glasses, and a laboratory coat. Avoid exposure to heat, open flames, or oxidising agents that could initiate uncontrolled polymerisation or combustion.

Storage Recommendations: Store in a tightly sealed container under an inert atmosphere (nitrogen or argon) at 2–8 °C or as specified on the product label and certificate of analysis for SKU D729417. Addition of a radical inhibitor (polymerisation inhibitor) such as 4-tert-butylcatechol (TBC) or hydroquinone monomethyl ether (MEHQ) during storage is common practice for vinyl-bearing reagents to extend shelf life.

Regulatory and Safety Information: Researchers must consult the Safety Data Sheet (SDS) provided by Aladdin Scientific for SKU D729417 before use. The SDS contains confirmed GHS hazard classifications, first-aid measures, disposal guidance, and transport information. Do not rely solely on this article for safety decisions.