Phenyltriacetoxysilane: Properties, Reactivity & Lab Uses
Phenyltriacetoxysilane: Properties, Reactivity & Lab Uses
Phenyltriacetoxysilane is a reactive organosilane compound bearing three acetoxy leaving groups and one phenyl substituent on silicon, making it a versatile reagent for surface functionalization, silicone crosslinking, and organometallic synthesis.
- Chemical Name
- Phenyltriacetoxysilane
- Molecular Formula
- C₈H₁₀O₆Si
- CAS Number
- 4130-08-9
- Molecular Weight
- 242.24 g/mol
- Functional Groups
- Three acetoxy (–OC(O)CH₃) groups and one phenyl group on silicon
- Key Reactivity
- Hydrolyzes in the presence of moisture to release acetic acid and form phenylsilanetriol intermediates
- Primary Applications
- Surface modification, silicone crosslinking, organosilane synthesis
Chemical Structure and Physical Properties
Phenyltriacetoxysilane (CAS 4130-08-9) is an organosilane reagent with the molecular formula C₈H₁₀O₆Si and a molecular weight of approximately 242.24 g/mol. Its silicon center is tetrahedrally coordinated, bearing one phenyl ring and three acetoxy (–OC(O)CH₃) leaving groups. This structural arrangement imparts high electrophilicity to the silicon atom, facilitating nucleophilic substitution reactions.
The compound is typically encountered as a colorless to pale-yellow liquid with a characteristic acetic-acid-like odor arising from partial hydrolysis upon exposure to atmospheric moisture. It is soluble in common organic solvents such as dichloromethane, toluene, tetrahydrofuran, and ethyl acetate, but reacts with water and protic solvents. Because the acetoxy groups are moderately reactive leaving groups, Phenyltriacetoxysilane occupies a useful middle ground between the highly reactive chlorosilanes and the slower-reacting alkoxysilanes, enabling controlled reactivity under mild conditions.
Hydrolysis and Condensation Chemistry
The defining chemical behavior of Phenyltriacetoxysilane is its hydrolysis. Upon contact with water, each acetoxy group undergoes hydrolysis to yield acetic acid and a silanol (Si–OH) group. The intermediate phenylsilanetriol (C₆H₅Si(OH)₃) is a trifunctional silanol that spontaneously undergoes condensation to form siloxane (Si–O–Si) linkages. This sequence — hydrolysis followed by condensation — is the basis for both surface-modification and crosslinking applications.
Compared with chlorosilanes, Phenyltriacetoxysilane generates acetic acid rather than hydrochloric acid as the byproduct, which is generally less corrosive and easier to handle in open-bench settings. The rate of hydrolysis can be modulated by pH: acidic conditions protonate the silanol and retard condensation, favoring the formation of oligomeric or polymeric siloxane networks when the pH is subsequently raised. This pH sensitivity enables researchers to tune the degree of polymerization and the morphology of the resulting siloxane matrix.
It is important to note that acetic acid release can still affect acid-sensitive substrates or formulations; reaction conditions and substrate compatibility should be evaluated on a case-by-case basis.
Laboratory Applications
Surface Functionalization: Phenyltriacetoxysilane is used to introduce phenyl groups onto hydroxyl-bearing surfaces such as silica, glass, silicon wafers, and metal oxides. The phenyl functionality imparts hydrophobicity, π–π stacking capacity, and compatibility with aromatic analytes, making treated surfaces useful in chromatography stationary phases, sensor platforms, and thin-film fabrication.
Silicone Crosslinking: As a trifunctional silane, it serves as a crosslinker in silicone formulations, contributing to network formation and improved mechanical properties. The phenyl substituent enhances thermal stability and refractive index of the resulting silicone material relative to alkyl-substituted analogs.
Organometallic and Polymer Synthesis: Researchers employ Phenyltriacetoxysilane as a building block for phenyl-containing polysiloxanes, hybrid organic–inorganic materials (e.g., ORMOSIL networks), and as a silylating agent for oxygen-nucleophile substrates where controlled acetoxy release is advantageous over chlorosilane routes.
Adhesion Promotion: In formulated adhesives and coatings, acetoxysilane-based primers improve interfacial adhesion between organic polymer matrices and inorganic substrates by forming covalent Si–O bonds at the interface.
Handling, Storage, and Safety Considerations
Moisture Sensitivity: Phenyltriacetoxysilane is moisture-sensitive and must be stored in tightly sealed containers under an inert atmosphere (nitrogen or argon) away from humidity. Prolonged exposure to air will cause hydrolysis, leading to the release of acetic acid and gelation of the product.
Personal Protective Equipment: Appropriate PPE including chemical-resistant gloves, safety goggles, and a lab coat should be worn during handling. Work should be performed in a well-ventilated fume hood, as acetic acid vapor released upon hydrolysis can be irritating to the respiratory tract, eyes, and skin.
Storage Conditions: Store at room temperature (15–25 °C) in a dry location, away from incompatible materials including strong oxidizers, strong bases, and water. Consult the Safety Data Sheet (SDS) supplied by Aladdin Scientific for full hazard information, first-aid measures, and disposal guidance before use.
Waste Disposal: Dispose of waste in accordance with local, regional, and national regulations. Hydrolyzed material and acetic acid-containing waste should be neutralized appropriately before disposal.
Purity, Specifications, and Ordering Information
Aladdin Scientific offers Phenyltriacetoxysilane (SKU: P168034) for research and development use. Researchers should consult the current product page or contact Aladdin Scientific's technical support team for the most up-to-date specifications, including purity grade, available package sizes, and certificate of analysis (CoA) details.
When evaluating reagent suitability, consider the required purity level for your application. Higher-purity grades minimize interference from hydrolysis byproducts and impurities in sensitive surface-modification or spectroscopic experiments. Bulk quantities may be available for scale-up studies; inquire with the procurement team for pricing and lead times.
Proper documentation including SDS, CoA, and technical data sheets is available upon request and is recommended for compliance with institutional safety and quality-management requirements.
Frequently asked questions
How should Phenyltriacetoxysilane be stored to prevent degradation?
Phenyltriacetoxysilane should be stored in tightly sealed containers under an inert gas (nitrogen or argon) at room temperature in a dry location, away from moisture, strong oxidizers, and strong bases. Exposure to atmospheric humidity will initiate hydrolysis, releasing acetic acid and potentially gelling the reagent.
What byproduct is released when Phenyltriacetoxysilane reacts with moisture, and why does it matter?
Hydrolysis of Phenyltriacetoxysilane releases acetic acid as the stoichiometric byproduct. While acetic acid is less corrosive than hydrochloric acid (released by chlorosilane analogs), it can still affect acid-sensitive substrates, catalysts, or biological systems. Adequate ventilation and compatibility testing with target substrates are therefore recommended.
What advantages does Phenyltriacetoxysilane offer over chlorosilane reagents in surface modification?
Compared with chlorosilanes, Phenyltriacetoxysilane generates acetic acid rather than corrosive hydrochloric acid upon hydrolysis, reducing equipment corrosion risk and simplifying byproduct handling. Its moderate reactivity also allows better control over the silylation process, and it is less sensitive to trace moisture in ambient conditions than the most reactive chlorosilanes.
Is Phenyltriacetoxysilane suitable for biological or biomedical surface-modification applications?
While Phenyltriacetoxysilane can chemically modify hydroxyl-bearing surfaces relevant to biomedical devices, researchers must carefully consider acetic acid release during hydrolysis, which may affect biological compatibility. Thorough washing and characterization of modified surfaces, along with appropriate cytotoxicity or biocompatibility assessments, are required before any biological use.
References
- Plueddemann, E. P. Silane Coupling Agents, 2nd ed.; Plenum Press: New York, 1991.
- Arkles, B. Silane Coupling Agent Chemistry. Gelest, Inc. Technical Library.
- Iler, R. K. The Chemistry of Silica; Wiley-Interscience: New York, 1979.
Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.