Quaternary phosphonium compounds

The reaction of higher alkyl chlorides with tin metal at 235°C is not practical because of the thermal decomposition which occurs before the products can be removed from the reaction zone. The reaction temperature necessary for the formation of dimethyl tin dichloride can be lowered considerably by the use of certain catalysts. Quaternary ammonium and phosphonium iodides allow the reaction to proceed in good yield at 150—160°C (109). An improvement in the process involves the use of amine—stannic chloride complexes or mixtures of stannic chloride and a quaternary ammonium or phosphonium compound (110). Use of these catalysts is claimed to yield dimethyl tin dichloride containing less than 0.1 wt % trimethyl tin chloride. Catalyzed direct reactions under pressure are used commercially to manufacture dimethyl tin dichloride. 

P. Beck, Quaternary Phosphonium Compounds, in Organic Phosphorus Compounds, G. M. Kosolapoff and L. Maier, (eds.), Vol. 2, John Wiley-Interscience, New York, 1972, Chap. 4. 

Quaternary arsonium compounds are in general reduced at potentials 0.3 V less negative than those of the corresponding phosphonium salts [207]. The ease of cleavage of the different groups is mostly similar to that in the phosphonium compounds, but some differences are found. 

MPIC Cations Ion-pair formation neutral HC1 Hexane-sulfonic acid Octane-sulfonic acid In addition to the cations listed under HPIC alkylamines, alkanolamines, quaternary ammonium compounds, cationic surfactants, sulfonium compounds, phosphonium compounds... 

Quaternary Phosphonium Compound Latent Accelerators for Anhydride-Cured Epoxy Resins... 

Most of the data reported here will be concerned with bisphenol A epoxy resin systems cured with the liquid anhydride, 1-methyltetrahydrophthalic anhydride (the Union Carbide commercial designation for this material is ZZLA-0334). However, these quaternary phosphonium compounds have also been shown to be effective with other anhydrides such as hexahydrophthalic anhydride (HHPA). 

Different Quaternary Phosphonium Compounds Evaluated. Seven different quaternary phosphonium salts were evaluated in this work ... 

With the exception of TPEPI, supplied by Arapahoe Chemical Company, Boulder, CO, all of the phosphonium compounds were supplied by Cincinnati Milacron, Reading, OH. The chemical structures of the various quaternary phosphonium compounds are shown in Table I. 

Most of the evaluation studies were made using a 1 1 stoichiometric bisphenol A epoxy-anhydride formulation. The various quaternary phosphonium compounds were added at a 0.01 to 0.25Z level (based on the combined anhydride and epoxy resin weights). With the exception of MTPP-DMP, which showed partial insolubility in the resin formulation, excellent solubilities at ambient temperature were found. 

Electrical Data. The electrical properties of cured specimens of the epoxy resin, containing various quaternary phosphonium compounds, were obtained on 2 in. diameter discs (0.125 in. to 0.25 in. thick) using standard procedures (ASTM D150-65T). In these tests, the power factor (100 x tan 6) and dielectric constant (e ) data were usually measured at 150 C (and a frequency of 60 Hz) on resin samples which had been cured for 16 h at 135 C + 5 h at 150 C. 

Table IV. Electrical Properties of Cured Epoxy-Anhydride Resins Containing Various Quaternary Phosphonium Compounds ...

Quaternary Phosphonium Compound Z Power Factor (100 X tan 6) Dielectric Constant (e )... 

The Initiation Mechanism with Phosphonium Compounds. Although further experimental data are needed to give a fuller understanding of the reaction mechanisms involved in the latent acceleration effect of these quaternary phosphonium compounds in epoxyanhydride resins, there is definite indication, at this stage, that the mechanism does not involve the decomposition of the phosphonium compound to the free phosphine species (16). The initiation mechanism probably involves the formation of hydrogen-bonded phosphonium-epoxy or phosphonium-anhydride complexes which rearrange on the application of heat to form activated species resulting in polymerization of the epoxy-anhydride components ( > ... 

Quaternary phosphonium compounds have been found to be extremely effective latent accelerators for anhydride-cured epoxy resins employed in electrical insulation applications. Used at very low concentrations (0.01 to 0.25% level) in these resins, they have been found to give very fast gel times at elevated temperatures combined with very good storage stability properties at room temperature. Results show that the quaternary phosphonium compounds having non-halide anions give the best compromise of gel reactivity, storage stability and electrical properties. Comparison with other types of latent accelerators reveal that the quaternary phosphonium compounds are among the most effective additives yet discovered for epoxy-anhydride resin systems. 

Cationic polymers can be grouped in three categories ammonium (primary, secondary, tertiary, and quaternary) sulfonium and phosphonium compounds. Of these, the ammonium-based polymers have been the most popular, because phosphonium compounds have not been synthesized to high molecular weights (2-8), and sulfonium monomers are generally unstable and less readily available than quaternary ammonium monomers (9-i2). 

A number of methods used for preparing phosphonium compounds has already been indicated on p. 7. Some tetra-alkylphosphonium hydroxides may be produced by heating white phosphorus and the corresponding alcohol above 250° C. for a long period. The compound PgHgg reacts with alkyl iodides to form quaternary compounds, and the latter also occur when trialkylphosphines react with alkyl halides. There are also special methods of preparation applying only to individual derivatives. The iodides are converted into the hydroxides by treatment with moist silver oxide, and bromides, cyanides, carbonates, acetates, oxalates and sulphates are similarly obtained when the appropriate silver salt is used. Such salts also result when the hydroxides are treated with the corresponding acids. 

The mixed quaternary phosphonium compounds are prepared as indicated by the following equations ... 

In the new process [112], [113] methylation is carried out with a phase transformation catalyst based on a quaternary ammonium or phosphonium compound (Fig. 34) in the present of a linear polyether in a two-phase mkture. Methanol is no longer used as the reaction medium and so energy-intensive distillation ceases to be necessary. Toxic dimethyl sulfate is replaced by methyl chloride as the methylating agent. The catalyst is recycled. Only spent catalyst with filtration residue are combusted as waste. 

Phosphorus-containing flame retardants are suitable for polar polymers such as PVC, but for polyolefins their action is not sufficient. In this case they are used together with Sb203 and with halogenated compounds. Alkyl-substituted aryl phosphates are incorporated into plasticized PVC and modified PPO (Noryl) to a great extent for other plastics they are less important. Quaternary phosphonium compounds are recommended as flame retardants for ABS and polyolefins. 

Proban Phosphoric acid esters, quaternary phosphonium compounds Albright and Wilson. London, U.K. 

Wolff, M.O. Alexander, K.M. Beider, G. Uses of quaternary phosphonium compounds in phase transfer catalysis. Chini. Oggi 2000. 18. 29-32. 

If alkyl halides are heated with phosphonium iodide in the presence of zinc oxide at 100-180 C, progressive alkylation takes place and the mixture of primary, secondary and tertiary phosphines can be separated by fractional distillation (6.29, 6.30). In the absence of zinc oxide, tertiary phosphines and quaternary phosphonium compounds are the favoured products (6.31,6.38). 

A mixture of tertiary phosphine and quaternary phosphonium compound is produced when phosphonium iodide is heated with a lower alcohol. 

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