Mechanism of phase-transfer catalysis

Landini, Dario; Maia, Angelamaria; Montanari, Fernando

doi:10.1039/c39770000112

Cited by 60 publications

(34 citation statements)

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“…24 More recently, interesting data have been available about the auto-association of quaternary phosphonium salts, that is higher in cyclohexane than in chlorobenzene. 25 We have found that on the progressive addition of dimethyldodecylamine to a triflic acid solution in CH2Cl 2 , there is first a large increase of the conductivity (assigned to the formation of bulky ions of high K0 ) followed by a decrease at higher ammonium salts concentrations, showing the lower conductivity of the equimolar salt [HN(CH 3 h(C 12 H 25 )] +, CF 3 S0 3 -. With a lowering of the dielectric constant of the medium, one may expect an increase of the number of acid molecules solvating the anion, giving lower initiation yields, more bulky counter-ions and more reactive ionic species.…”

Section: Influence Of Counter-ion Complexation On Cationic Pol Ymericmentioning

confidence: 99%

Recent Evidence for the Association of Initiator with Counter Ion in Cationic Polymerization

Sigwalt

Sauvet

1980

Polym J

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ABSTRACT:Spectroscopic studies (by UVand NMR) of the reaction of 1,1-diphenylethylene with trifiuoromethanesulfonic acid have been made in dichloromethane, at temperatures (-30°C to -90°C) at which the carbocations are stable. A 33% average yield in carbocations with respect to CF3S03H was found in a large concentration range and interpreted as a complexation of the CF3S03 -anion by 2 inactive acid molecules. For 3-phenylindene, the yield was 50%. Further model studies have shown that various trifiic salts (of Ph 3 C +, Bu4 N +, Ag +) are strongly solvated by trifiic acid, and the results are in agreement with the formation of complex counter ions of structures A -(HA); A -(HA)2 and A -(HAh. The implications of these results for cationic polymerizations are discussed and particularly the interpretation of various observations made in the literature about the effect of common salt addition and of a variation of the dielectric constant of the medium.

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Section: Influence Of Counter-ion Complexation On Cationic Pol Ymericmentioning

confidence: 99%

Recent Evidence for the Association of Initiator with Counter Ion in Cationic Polymerization

Sigwalt

Sauvet

1980

Polym J

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“…Studies of extraction equilibria have considerable practical importance in relation to phase-transfer catalysis (7,8) and analytical applications (9), and are also frequently used for comparative purposes in estimating the complexing capabilities of newly synthesized ligands (3,10, 11). At a more fundamental level, a detailed analysis of the various equilibria involved in the overall extraction process is of some intrinsic interest, and is directly relevant to a better understanding of carrier-mediated ion transport in biological and synthetic membranes.…”

Section: Introductionmentioning

confidence: 99%

“…[Traduit par la revue] Introduction Efficient extraction of alkali-metal salts from aqueous media into organic solvents is often observed in the presence of macrocyclic complexing agents. This is especially true when the charge on the accompanying anion is highly delocalized as, for example, in the picrate anion (1-6).Studies of extraction equilibria have considerable practical importance in relation to phase-transfer catalysis (7,8) and analytical applications (9), and are also frequently used for comparative purposes in estimating the complexing capabilities …”

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confidence: 99%

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Extraction of alkaline-earth metal ortho- and para-nitrophenoxides from aqueous media by crown ether and cryptand complexing agents

Cox¹,

Buncel²,

Shin³

et al. 1986

Can. J. Chem.

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. Can. J. Chem. 64,920 (1986).A study has been performed on the extraction of alkaline-earth metal ortho-and para-nitrophenoxides, from aqueous medium into methylene chloride, in the presence of crown ether and cryptand complexing agents. The results are analyzed in terms of the various constituent complexation and extraction equilibria involved. Comparison is drawn with our previously reported study on extraction of potassium p-nitrophenoxide. The different anion stoichiometries in the two systems result in relatively more favorable extraction of M+ systems at low anion concentrations. Furthermore, while extraction of MX (X = o-or p-nitrophenoxide) can be carried out in the presence of excess MOH, this is not possible in the case of MX2 due to the limited solubility of M(OH)2. The addition of excess MOH leads to more efficient extraction of M+-phenoxides and prevents hydrolysis to free phenols. A noteworthy point in both MX and MX2 systems is that at high concentrations of complexing agent a saturation effect occurs, which limits the overall extent of extraction achievable. Under these conditions the extraction is governed by the equilibrium constant, Kdcs, representing the partitioning of the complexed salt between the aqueous and organic phases, and is independent of the amount of ligand present. [Traduit par la revue] Introduction Efficient extraction of alkali-metal salts from aqueous media into organic solvents is often observed in the presence of macrocyclic complexing agents. This is especially true when the charge on the accompanying anion is highly delocalized as, for example, in the picrate anion (1-6).Studies of extraction equilibria have considerable practical importance in relation to phase-transfer catalysis (7,8) and analytical applications (9), and are also frequently used for comparative purposes in estimating the complexing capabilities

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“…In the case where the PT catalyst is very organophilic and exclusively partitions in the organic phase, the reaction mechanism is explained by the BrandstromMontanari modification of Starks' extraction mechanism (Brandstrom, 1977;Landini et aL, 1977). Here, the ion exchange occurs at the interface or within an interfacial boundary layer.…”

Section: Reaction Under Neutral or Acidic Conditionsmentioning

confidence: 99%

Triphase catalysis: mass transfer and kinetic studies

Glatzer¹

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Mechanism of phase-transfer catalysis

Cited by 60 publications

References 0 publications

Recent Evidence for the Association of Initiator with Counter Ion in Cationic Polymerization

Recent Evidence for the Association of Initiator with Counter Ion in Cationic Polymerization

Extraction of alkaline-earth metal ortho- and para-nitrophenoxides from aqueous media by crown ether and cryptand complexing agents

Triphase catalysis: mass transfer and kinetic studies

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