- Removal of alkyl alkanesulfonate esters from alkanesulfonic acids and other organic media
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Methods of removing alkyl alkanesulfonate esters from aqueous or anhydrous compositions are provided. The invention provides methods for the conversion of alkyl alkanesulfonate esters of the formula RSO3R′ to the corresponding acids of the formula RSO3H. The alkyl alkanesulfonate esters are present in an organic medium, which may contain significant amounts of water or which may be anhydrous or substantially anhydrous. In some embodiments, the invention provides methods for purifying aqueous or anhydrous alkanesulfonic acids by removing alkyl alkanesulfonate esters.
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Page/Page column 6
(2008/06/13)
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- Mechanism and Anion Activation in Solid-Liquid Phase-transfer Reactions Catalysed by Cyclophosphazenic Polypodands. Comparison with Cyclic Analogue Crown Ethers
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A kinetic study of the nucleophilic substitution of the methanesulfonic group by anions (Cl-, Br-, I-, SCN-, C6H5O-, C6H5CH2COO-) catalysed by cyclophosphazenic polypodands has been performed under solid-liquid phase-transfer conditions.The results obtained show that the mechanism of PTC previously found for cyclic ligands (crown ethers, cryptands) also operates in the case of these open-chain ligands: the attack by the anionic nucleophile on the substrate occurs in the organic phase and is rate determining of the overall process.The nucleophilicity scales found (I- > C6H5O- ca.SCN- > C6H5CH2COO-; I- > Br- > Cl-) as well as the anion activation are comparable with those found for cyclic crown ethers.This indicates that the anionic reactive species involved are similar in the complexes of both ligands.
- Landini, Dario,Maia, Angelamaria,Podda, Gianni,Secci, Daniela,Yan, Yong Ming
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p. 1721 - 1724
(2007/10/02)
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- Linker compounds, linker-compound-ligands and linker-compound-receptors
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Novel immunoassay which utilizes an enzyme linked ligand or receptor wherein the enzyme is bacterial luciferase; mercantile kit useful in performing said immunoassay; and compounds utilized in performing said assay.
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- An Assessment of the Causes of the "Cesium Effect"
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Cesium alkanoates (chiefly the propionate) have been investigated for their solubility, nucleophilic, reactivity and degree of ion pairing in dimethylformamide (DMF) and, in some cases, dimethyl sulfoxide (DMSO) solutions. 133Cs NMR has been used to establish the degree of ion pairing.From the data obtained it is concluded that the cesium ion is virtually completely solvated and that the carboxylates are essentially free and highly reactive.The consequences of this effect on macrocyclization by means of nucleophilic substitution are discussed.
- Dijkstra, Gerard,Kruizinga, Wim H.,Kellogg, Richard M.
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p. 4230 - 4234
(2007/10/02)
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- Polymer-Supported Cryptands. Problems Arising in the Synthesis of Highly Loaded Polymers
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The attachment of a hydroxymethylcryptand to lightly loaded chloromethylpolystyrene (1 mequiv of Cl/g) cross-linked with divinylbenzene leads to polymer-supported cryptands that are highly efficient catalysts in anion-promoted reactions carried out under phase-transfer conditions.However, the condensation with polystyrenes having a higher content of chloromethyl groups occurs in low yields, apparently affording immobilized cryptands with very low catalytic activity.This behavior results from extensive structural modifications of the bicyclic ligand, most likely promoted by neighboring chloromethyl groups.
- Anelli, Pier Lucio,Montanari, Fernando,Quici, Silvio
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p. 4910 - 4914
(2007/10/02)
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- Polymer-Supported Phase Transfer Catalysis: Kinetics of a Bromide Ion Displacement Reaction and the Effect of Mass Transfer on the Global Rate of Reaction
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The bromide ion displacement reaction of n-octyl methanesulfonate catalyzed by polymer-bound phosphonium ion was studied and the effects of the phosphonium ion content and the degree of cross-linking on the intrinsic activity and the intraparticle diffusion were examined.The catalysts were prepared by quaternization of chloromethylated polystyrene with tri-n-butylphosphine.All experiments were carried out in a stirred tank reactor in the temperature range from 60 to 90 deg C and at ambient pressure.The intrinsic rate of reaction was proportional to the concentration of n-octyl methanesulfonate, and gradually increased with the concentration of potassium bromide in the aqueous phase.The instrinsic activity decreases with increases in the phosphonium ion content and the degree of cross-linking.The liquid-to-solid mass transfer resistance was insignificant at stirring speeds above 400 rpm under the present conditions.The intraparticle diffusion of n-octyl methanesulfonate was found to be an important factor controlling the global rate of reaction.The effective diffusivity of n-octyl methanesulfonate in polymer resin decreased remarkably with increase in the degree of cross-linking.Keywords - phase transfer catalyst; immobilization; polystyrene resin; anion displacement; n-octyl methanesulfonate; reaction kinetics; intraparticle diffusion
- Takeuchi, Hirofumi,Miwa, Yoshihisa,Morita, Shushi,Okada, Jutaro
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p. 409 - 417
(2007/10/02)
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- Studies on Triphase Catalysis: Effects on Structure of the Immobilized Quaternary Salt on the Catalytic Activity
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The catalytic activities of eight different types of catalyst (immobilized phase transfer catalyst) were examined in the displacement reaction of several anions with benzyl bromide and n-octyl methanesulfonate at 70 and 90 deg C, respectively.The catalysts were prepared by the reaction of 1percent cross-linked chloromethylated polystyrene with such tertiary amines as R3N (R=ethyl, n-propyl, n-butyl) and R(CH3)2N (R=ethyl, n-butyl, n-dodecyl, n-hexadecyl) and tri-n-butylphosphine.The catalytic activity for the reaction of n-octyl methanesulfonate increased with increasing size of the immobilized quaternary cation.The catalysts with bulky cations having different central atoms (-CH2N+(C4H9)3, -CH2P+(C4H9)3) showed almost the same catalytic activity in every reaction tested.Variation of the structure of the immobilized cation was concluded to modify the catalytic activity not only by changing the anion-cation interaction energy but also by changing the reaction environment around the active site.Keywords - triphase catalysis; phase transfer catalysis; anion displacement; quaternary cation structure; catalytic activity comparison; polystyrene resin; n-octyl methanesulfonate.
- Takeuchi, Hirofumi,Miwa, Yoshihisa,Morita, Shushi,Okada, Jutaro
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p. 823 - 831
(2007/10/02)
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- Reaction Mechanism and Factors Influencing Phase-Transfer Catalytic Activity of Crown Ethers Bonded to a Polystyrene Matrix
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Polymer-supported crown ethers 1 and 2 were prepared by reaction of 1percent cross-linked chloromethylated polystyrene, with (hydroxymethyl)- and (ο-hydroxynonyl)-18-crown-6, respectively.Their phase-transfer catalytic activity was tested in anion-promoted nucleophilic aliphatic substitutions and compared with that of structurally similar soluble crown ethers and of polymer-supported and soluble phosphonium salts.Catalytic efficiency of crown ethers 1 and 2 depends on a combination of three parameters: the nature of the nucleophile, the percent ring substitution, and the presence of a spacer chain.Complexation of potassium salts largely depends on the anion, with a high degree for soft nucleophiles like I- and SCN- and a lower degree for smaller and less polarizable nucleophiles like Br- and CN-.This corresponds to high and low catalytic efficiency, respectively.Spaced catalysts 2 are on the average 2-4 times more reactive than directly bonded catalysts 1.The extent of ring substitution noticeably influences catalytic activity, the variation depending on the nature of the nucleophile.With soft nucleophiles the observed rates progressively diminish as loading increases, following a linear correlation on a semilogarithmic scale, whereas with harder nucleophiles the observed rates reach a maximum at 30percent ring substitution.All reactions follow a pseudo-first-order kinetics, and rates are linearly dependent on molar equivalents of polymer-supported crown ethers.Hydrophilicity of catalysts and the extent of complexation increase with the extent of loading.Phenol is exclusively O-alkylated, even in the presence of the most hydrophilic catalysts.The data, as a whole, lead to the conclusion that the reactions occur in the organic shell surrounding a complexed crown ether, following a mechanism analogous to that demonstrated for immobili zed quaternary salts.
- Anelli, Pier Lucio,Czech, Bronislaw,Montanari, Fernando,Quici, Silvio
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p. 861 - 868
(2007/10/02)
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- Phase-Transfer Reactions Catalyzed by Lipophilic Cryptands and Dicyclohexano-18-crown-6: Dehydrating Effect of Concentrated Aqueous Alkaline Solutions
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A study of how the concentration of aqueous KOH affects the hydration and hence the reactivity of anions (Cl-, Br-, I-, SCN-, N3-) in aliphatic nucleophilic substitutions catalyzed by lipophilic cryptand (1a) and dicyclohexano-18-crown-6 (DCH18C6) (2) under phase-transfer conditions is reported.A comparison with the same reactions performed in classical liquid-liquid PTC and homogeneous anhydrous conditions is also included.Unlike quaternary onium salts, even at the highest KOH concentrations (53percent; ie., conditions in which aH2O ca. 0), water in the presence of 1a is not completely removed.Residual hydration depends on the nature of the anion and is the highest for anions with localized and/or less polarizable charge, such as Cl-, Br-, and N3-.As a consequence, rate constants noticeably increase in comparison with those found under conventional PTC conditions but do not reach those of anhydrous solutions.The different behavior of cryptates and quaternary salts is discussed on the basis of the different topology of the two systems.Behavior of crown ethers is in between that of quaternary salts and cryptates, since residual hydration in the presence of 53percent aqueous KOH is lower than that of cryptates, whereas anionic reactivity becomes practically identical with that found under anhydrous conditions.
- Landini, Dario,Maia, Angelamaria,Montanari, Fernando
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p. 2917 - 2923
(2007/10/02)
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- Nonhydrated Anion Transfer from the Aqueous to the Organic Phase: Enhancement of Nucleophilic Reactivity in Phase-Transfer Catalysis
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A systematic study of how the nature and concentration of the inorganic salt affect hydration and reactivity of anions transferred into the organic phase under conditions of phase-transfer catalysis (PTC) has been performed.The inorganic salt concentration in the aqueous phase up to saturated solution (= or > 6 M), does not affect the hydration and hence the reactivity of the anion in aliphatic nucleophilic substitutions.On the other hand, in concentrated aqueous alkaline solutions (50percent NaOH or 60percent KOH) unhydrated anions are transferred from the aqueous to the organic phase.The anionic reactivity thus becomes identical with that found under anhydrous homogeneous conditions, the rate enhancement being 13.0, 4.0, 2.6, and 1.4 times for Cl(1-), N3(1-), Br(1-), and I(1-), respectively.The same dehydrating effect was not observed with less concentrated alkaline solutions or with 50percent aqueous NaF.These data show the unique property of OH(1-) in producing conditions of virtually null water activity under PTC conditions.
- Landini, Dario,Maia, Angelamaria,Podda, Gianni
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p. 2264 - 2268
(2007/10/02)
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- Crown ethers as phase-transfer catalysts. A comparison of an ionic activation in aqueous-organic two-phase systems and in low polarity anhydrous solutions by perhydrodibenzo-18-crown-6, lipophilic quaternary salts, cryptands
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Anion-promoted nucleophilic substitutions carried out in aqueous-organic two-phase systems in the presence of catalytic amounts of perhydrodibenzo-18- crown-6 follow the classic mechanism of phase-transfer catalysis. The observed pseudo-first-order rate constants are linearly related to the concentration of complexed crown ether in the organic phase. The narrow reactivity range and the sequence found in the reaction between n-octyl methane-sulphonate and a homogeneous series of anions in the PhCl-H2O two-phase system (N 3- > I- ～ Br- > CN - > Cl- > SCN-) remain largely unaltered in anhydrous PhCl. From this point of view complexed crown ethers differ substantially from lipophilic quaternary salts and cryptates. Indeed, removal of the hydration sphere of the anions in going from two-phase to anhydrous conditions is balanced by a larger cation-anion interaction, resulting in a very small variation of anion reactivity. This indicates that, unlike cryptates, complexed crown ethers can hardly be considered as a source of 'naked anions.' A comparison is also reported among lipophilic crown ethers, quaternary salts, and cryptands as phase-transfer catalysts.
- Landini, Dario,Maia, Angelamaria,Montanari, Fernando,Pirisi, Filippo M.
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- Importance of Association Phenomena of Quaternary Onium Salts in the Organic Phase Responsible for the Course of Phase-Transfer-Catalysed Reactions
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As shown by vapour pressure osmometry quaternary ammonium- and phosphonium salts are associated in benzene and chloroform. The rate of the model reactions (1) and (2) is faster the higher the degree of association; in the two-phase system the rate is however slower due to the water content of the organic phase, which diminishes the association.Association phenomena are obviously essential for the "catalysis" in the two-phase-system.
- Horner, Leopold,Gerhard, Joachim
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p. 838 - 842
(2007/10/02)
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