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Trioctylphosphine oxide (CAS: 78-50-2)
Product Description
Trioctylphosphine oxide, commonly abbreviated as TOPO (CAS: 78-50-2), is an organophosphorus compound with the formula OP(C?H??)?. It appears as a white, opaque crystalline solid at room temperature, is air-stable, and has a slight characteristic odor. It is insoluble in water but soluble in organic solvents such as ethanol, ether, chloroform, benzene, and kerosene. As a typical Lewis base, TOPO has a partial negative charge on the oxygen atom, enabling it to coordinate with metal ions. It is widely used in solvent extraction, nanoparticle stabilization, and high-temperature chemical reactions, and serves as an important auxiliary agent in the fields of chemistry, materials science, and chemical engineering.
Uses
Solvent Extraction: As an efficient metal extractant, it is widely used in the hydrometallurgical industry for the separation and purification of metals such as uranium, thorium, rare earth elements, and transition metals. Its high lipophilicity allows it to dissolve in non-polar solvents like kerosene, while the polar phosphine oxide group can selectively bind to metal ions, achieving efficient separation and enrichment of metals. The high lipophilicity and polarity of TOPO are the key properties for this application, making it particularly suitable for uranium extraction.
Materials Science & Nanotechnology: Acts as a common capping ligand and stabilizer for nanoparticles. It can control the growth and size of nanoparticles (such as quantum dots, metal nanoparticles, and metal oxide nanoparticles) during synthesis, preventing particle aggregation. It is widely used in the preparation of high-quality nanomaterials with uniform size and good dispersion stability, especially in the synthesis of semiconductor nanocrystals like cadmium selenide (CdSe) quantum dots.
High-Temperature Chemical Reactions: Due to its high boiling point and excellent thermal stability, it serves as a high-temperature solvent and reaction medium for organic synthesis and catalytic reactions. It is suitable for reactions requiring elevated temperatures (such as condensation, cyclization, and rearrangement reactions) and can improve reaction efficiency and selectivity. It is also applicable to various coupling reactions including Buchwald-Hartwig Cross Coupling, Heck Reaction, and Suzuki-Miyaura Coupling as a ligand.
Chemical Analysis & Research: Used as a stationary phase additive in chromatography and a reagent in chemical analysis for the separation and detection of metal ions and organic compounds. It is also commonly used as a model compound and reaction auxiliary in biochemical and pharmaceutical research to study coordination chemistry and reaction mechanisms, and is suitable for extraction analysis applications.
Molecular Formula & Structure
- Molecular Formula: C??H??OP
- Molecular Weight: 386.63 g/mol (386.645 g·mol?1, precise value)
- IUPAC Name: Trioctyl-λ?-phosphanone; Trioctylphosphine oxide
- Synonyms: TOPO; Tri-n-octylphosphine oxide; Trioctylphosphane oxide; (Oct)?PO; TOPO®; MFCD00002083; BRN 1796648; PubChem Substance ID: 329747118; UNSPSC Code: 12352001; NACRES: NA.22
- EC Number: 201-121-3
- CAS Number: 78-50-2
- SMILES Code: CCCCCCCCP(=O)(CCCCCCCC)CCCCCCCC
- Chemical Structure: The molecule consists of a central phosphorus atom double-bonded to an oxygen atom and single-bonded to three n-octyl groups (-C?H??). The phosphorus-oxygen bond is highly polar, endowing the molecule with Lewis basicity and strong metal ion coordination ability. The three long-chain alkyl groups provide lipophilicity and steric hindrance, enhancing solubility in non-polar solvents and stabilizing the molecular structure. The linear formula can also be expressed as (CH?(CH?)?)?PO.
Physical & Chemical Properties
- Appearance: White, opaque crystalline solid, slight characteristic odor; stable in air, non-hygroscopic, and not prone to discoloration under normal temperature and pressure.
- Melting Point: 50–54 °C (lit. 50–52 °C, 52–55 °C); Boiling Point: 411.2 °C (at 760 mmHg), 201–202 °C/2 mmHg (lit.); Flash Point: 110 °C (closed cup, 230 °F; 383 K); non-flammable solid, stable at high temperatures (NFPA 704 fire diamond: 3 1 0).
- Density: 0.861 g/cm3 (20 °C); Refractive Index: 1.4600–1.4650 (20 °C); Solubility: <1 g/L in water, soluble in ethanol, ether, chloroform, benzene, and kerosene.
- Stability: Excellent thermal stability, decomposes only at temperatures above 300 °C; stable in neutral and weakly alkaline environments, decomposes slowly in strong acids; avoid contact with strong oxidizing agents to prevent oxidation and degradation.
- Toxicity: Moderately toxic; GHS labeling: signal word "Danger", hazard statements H315 (causes skin irritation), H318 (causes serious eye damage); swallowing may be harmful, and skin contact may cause irritation. It may cause severe eye irritation and damage. It is highly toxic to aquatic organisms and may have long-term adverse effects on the aquatic environment; precautionary statements include P264, P280, P302+P352, P305+P351+P338, P310, P332+P313, P362.
Synthesis & Storage
- Synthesis: The main synthetic method is the oxidation of trioctylphosphine. Trioctylphosphine is prepared by alkylation of phosphorus trichloride, followed by oxidation with an oxidizing agent (such as hydrogen peroxide, peracetic acid, or air) to generate TOPO. The product is purified by recrystallization (using ethanol or hexane as the solvent) or distillation to obtain high-purity TOPO.
- Storage: Sealed and stored in a cool, dry, and well-ventilated warehouse; avoid direct sunlight and moisture. Recommended storage temperature: below 30 °C (can be stored at room temperature under proper conditions). Store separately from strong acids, strong oxidizing agents, and food. Shelf life: 24 months when unopened and stored properly; use as soon as possible after opening to prevent moisture absorption and contamination.
- Safety: Operate in a well-ventilated fume hood; wear nitrile gloves, chemical protective goggles, and a lab coat. Avoid contact with skin, eyes, and mucous membranes; avoid inhalation of dust or vapor. In case of skin contact, wash with plenty of water and soap; in case of eye contact, rinse cautiously with water for several minutes and seek medical advice immediately. Dispose of waste in accordance with relevant environmental regulations.
