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Interfacial Catalysis at Oil/Water Interfaces
Published in Alexander G. Vdlkdv, Interfacial Catalysis, 2002
In addition to consideration of the structure-activity relationships, the criteria for selecting a PTC catalyst usually include the following features: (1) stability, (2) cost and availability, (3) removal, recovery, and recycling, (4) toxicity, and (5) waste treatment, etc. The tetrabutylammonium cation is the most widely used quaternary ammonium cation. It is commercially available in a wide variety of anions at moderate cost and has a unique application in tri-liquid-phase catalysis. It can also be easily separated and recovered by extraction, then recycled. Methyltributylammonium cation will become a popular catalyst due to its high reactivity in transfer rate limited PTC reactions, its lower toxicity than most quaternary ammonium cations, and its low price. Methyltrioctylammonium cation is also commercially popular and is organophilic and anion activating enough to catalyze most intrinsic reaction rate limited PTC reactions and is accessible enough to catalyze most transfer rate limited PTC reactions. In comparison with quaternary ammonium salts, quaternary phosphonium salts are generally more thermally stable and more active under neutral or acidic conditions, but less stable under alkaline conditions. Although they have been used in a variety of PTC reactions, the greater cost compared to quaternary ammonium salts limits their industrial applications. Toxic quaternary arsonium salts are used mainly for comparative processes. Tetraphenylarsonium salts are useful for PTC analytical titration of highly organophilic unsaturated compounds [3]. The triphenylsulfonium cation is stable under strong alkaline conditions and is effective for catalyzing the PTC displacement of 1-bromo-octane with NaCN,NaOPh,KSCN, and KI [107].
Symbols, Terminology, and Nomenclature
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
RPH2, R2PH and R3P (R not equal to H) are called primary, secondary and tertiary phosphines, respectively. [5] Phosphonium compounds - Salts (and hydroxides) [R4P]+X- containing tetracoordinate phosphonium ion and the associated anion. [5] Phosphonium ylides - Compounds having the structure R3P+C-R2 R3P=CR2. Also known as Wittig reagents. [5] Phosphorescence - The process by which a molecule is excited by light to a higher electronic state and then undergoes a radiationless transition to a state of different multiplicity from which it decays, after some delay, to the ground state. The emitted light is normally of longer wavelength than the exciting light because vibrational energy has been dissipated. Photoelectric effect - The complete absorption of a photon by a solid with the emission of an electron. Photon - An elementary particle of zero mass and spin 1. The photon is involved in electromagnetic interactions and is the quantum of electromagnetic radiation. Photon stimulated desorption (PSD) - See Techniques for Materials Characterization, page 12-1. Pinacols - Tetra(hydrocarbyl)ethane-1,2-diols, R2C(OH)C(OH)R2, of which the tetramethyl example is the simplest one and is itself commonly known as pinacol. [5] Pion - An elementary particle in the family of mesons. Pions have zero spin and may be neutral or charged. They participate in the strong interaction which holds the nucleus together. pK* - The negative logarithm (base 10) of an equilibrium constant K. For pKa, see Acid dissociation constant. Planck constant (h)* - The elementary quantum of action, which relates energy to frequency through the equation E = h. Planck distribution - See Black body radiation Planck function - A thermodynamic function defined by Y = -G/T, where G is Gibbs energy and T thermodynamic temperature. [2] Plasma - A highly ionized gas in which the charge of the electrons is balanced by the charge of the positive ions, so that the system as a whole is electrically neutral. Plasmon - A quantum associated with a plasma oscillation in the electron gas of a solid. Point group* - A group of symmetry operations (rotations, reflections, etc.) that leave a molecule invariant. Every molecular conformation can be assigned to a specific point group, which plays a major role in determining the spectrum of the molecule. Poise (P) - A non-SI unit of viscosity, equal to 0.1 Pa s. Poiseuille's equation - A formula for the rate of flow of a viscous fluid through a tube:
Methyltriphenylphosphonium carboxylate ionic liquids: Green synthesis, adsorption and aggregation behavior in aqueous solution
Published in Journal of Dispersion Science and Technology, 2020
Shengfu Duan, Yajie Jiang, Tao Geng, Hongbin Ju, Yakui Wang
Phosphonium-based ionic liquids (ILs) have recently received much interest and widely applied in various fields, including catalysis,[1] organic synthesis,[2–4] electrochemistry,[5] nanomaterial[6,7] and antibacterial materials[8] due to their unique properties. Generally, phosphonium-based ILs are prepared by quaternarization of tertiary phosphine with halogenated alkanes or dimethyl sulfate (DMS).[9,10] However, preparation of this ILs starting from halogenated hydrocarbons or DMS is not environment-friendly. It can cause the problems of environmental pollution and equipment corrosion because the toxicity and corrosion of halogenated alkanes and DMS. An alternative approach to solve the problem is to select green alkylating agents. In 1992, dimethyl carbonate (DMC) had been registered in Europe for nontoxic chemicals, known as “green” chemicals. And, the unique properties of DMC grant them great potential in practical applications.[11,12] With the continuous research on DMC, researchers have focused on the use of DMC as green alkylating agents. Fabris et al.[13] reported the synthesis of methylphosphonium ILs based on the use of DMC.