Quaternary Ammonium Sites Research Articles

Treatment of wood with aminofunctional silanes for protection against wood destroying fungi

AbstractDifferent aminofunctional silanes were tested for their suitability to preserve wood against basidiomycetes in a mini-block experiment according to EN 113. High effectiveness against the brown rot fungusConiophora puteanawas maintained over prolonged exposure times of up to 18 weeks. Resistance against the white rot fungusTrametes versicolorwas only enhanced in the initial phase of exposure (6 weeks); after longer exposure times of 18 weeks, considerable mass losses were observed. It was shown that the antifungal resistance was caused by the amino groups of the oligomeric silane systems, while alkyl groups, which influence the water uptake of wood, only had a minor impact. For effective protection, acidic conditions of the treatment solution were important; this promotes the formation of cationised amino groups (ammonium). The silane quaternary ammonium compound (Si-QAC) 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium chloride was applied in combination with an oligomeric silane system to incorporate quaternary ammonium sites into a SiO2matrix via a sol-gel process. This combined treatment significantly enhanced the decay resistance of pine wood againstC. puteana.

Halide anion solvation and recognition by a macrotricyclic tetraammonium host in an ionic liquid: a molecular dynamics study

We report a molecular dynamics study of halide anions X− and their inclusion complexes X− ⊂ L4+ with a macrotricyclic tetrahedral host L4+ built from four quaternary ammonium sites, in an ionic liquid (IL) based on the 1-butyl-3-methylimidazolium (BMI+) cation and the PF6− anion. The “dry” and “humid” forms of the [BMI][PF6] IL are compared, showing the importance of IL ions in the “dry” IL and, in some cases, of water molecules in the “humid” IL. In the “dry” IL the F−, Cl−, Br− and I− uncomplexed halides are surrounded by 4–5 BMI+ cations whose binding mode evolves from hydrogen bonding to facial coordination along this series. Solvent humidity has the largest impact on the solvation of F− whose first shell BMI+ cations are all displaced by H2O molecules, while the first solvation shell of Cl−, Br− and I− comprises 3–4 BMI+ cations plus ca. 4 H2O molecules. The solvation of the L4+ host and of its X− ⊂ L4+ complex mainly involves PF6− anions in the “dry” IL, and additional H2O molecules in the “humid” IL. The question of anion binding selectivity is addressed by free energy perturbation calculations which predict that, in the “dry” liquid, F− is preferred over Cl−, Br− and I−, which contrasts with the aqueous solution where L4+ is selective for Cl−. In the “humid” liquid however, there is no F−/Cl− discrimination, showing the importance of “small amounts” of water on the complexation selectivity.

The removal of perchlorate from groundwater by activated carbon tailored with cationic surfactants

In rapid small-scale column tests, cationic surfactant-tailored activated carbons (ACs) effectively removed perchlorate to below detection levels for up to 30 times longer than virgin AC. By pre-loading bituminous AC with dicocodimethylammonium chloride, tallowtrimethylammonium chloride, cetyltrimethylammonium chloride, or cetylpyridinium chloride, 75 ppb perchlorate was removed for 27,000–35,000 bed volumes before the effluent perchlorate rose above 1 ppb. These tests employed a natural groundwater that also contained 30 mg/L sulfate, 26 mg/L nitrate (as NO 3 −), and other ions. By the time of 25 ppb perchlorate breakthrough, 7.3–10.1% of quaternary ammonium sites had perchlorate associated with them. Although some of the surfactants leached out of the tailored carbon beds (0.6–21.2% of the amount loaded), the leached surfactant could be removed to below detectable limits with a virgin AC polishing bed that chased the tailored bed.

Electrostatic ion chromatography using a carboxybetaine-type zwitterionic surfactant as the stationary phase.

A carboxybetaine-type zwitterionic stationary phase obtained by immobilizing Mitsubishi Reagent EF-700 (C(8)F(17)SO(2)NHC(3)H(6)N(+) (CH(3))(2)-C(2)H(4)-COO(-)) onto a reversed-phase column was used for chromatographic separation of ions. When aqueous electrolyte solutions having higher pH values (>8) were used as eluents, the model analyte ions (NO(2)(-), H(2)PO(4)(-), Cl(-), Br(-), NO(3)(-), ClO(3)(-), I(-) and SCN(-)) were co-eluted and appeared at the void volume of this HPLC system. However, when aqueous electrolyte solutions having lower pH values (<5.5) were used as eluents, these anions were well retained and separated. Furthermore, when acetate buffers (NaAc/HAc) were used as eluents, plots of log k' (k', retention factor) versus pH of eluents (at constant [NaAc+HAc]), and log k' versus log [NaAc+HAc] (at constant pH), were linear with negative slopes. Breakthrough curves for acid solutions obtained using conductivity detection showed that H(+) ions and their conjugate anions were both retained on the stationary phase and the degree of binding was found to be independent of the acid species used. The degree to which the eluent cation was bound onto the carboxylate functionality of the zwitterion was found to exert a major effect on the retention of analyte anions. A strongly bound cation, such as H(+), reduced electrostatic repulsion effects exerted by the carboxylate functionality on analyte anions, so that they could freely access the quaternary ammonium sites on the zwitterion. It is concluded based on these experimental results that both the charges on the zwitterionic stationary phase make meaningful contributions to the separation of the analyte ions.

An Anomalous Behavior of Anion-Exchange Membranes with Low Concentration of Quaternary Ammonium Sites: An Apparent Selectivity to Bicarbonate and Phosphate, and Its True Nature

It is shown that anion-selective electrodes with low concentration of quaternary ammonium sites exhibit an apparent response and selectivity to HCO3− and HPO42− ions in aqueous solutions. It is, however, detected that none of these ions is the potential-determining, and the electrodes actually respond to OH−. The selectivity to OH− is due to unidentified anionic impurities in the plasticizer, and vanishes with aging of the electrodes. Additional purification of the plasticizer eliminates the selectivity to OH−, which, however, is restored after intentional addition of negatively charged sites. Quaternary ammonium sites with longer alkyl chains provide higher selectivity to OH− suggesting that this selectivity originates from steric hindrances against bigger anions.

Macrotricyclic quaternary tetraammonium receptors: halide anion recognition and interfacial activity at an aqueous interface. A molecular dynamics investigation.

We report a molecular dynamics study of the halide inclusion complexes X(-) subset L(4+) of a macrotricyclic tetrahedral receptor L(4+) built from four quaternary ammonium sites connected by six (CH(2))(n) chains. The hydrophilic/hydrophobic character of the complexes is investigated at a water/chloroform interface, represented explicitly and, despite their +3 charge and "spherical" shape, they are found to display amphiphilic behavior and to concentrate at the interface. The more lipophilic N-substituted CH(2)phi derivative, as well as less charged models are more surface active than the N-Me substituted host. In relation with the Hofmeister series, I(-) exo neutralizing counterions are compared with Cl(-) anions and are found to sit closer to the interface, which becomes more neutral. The "macrocyclic interfacial effect" is investigated by a comparison of L(4+) complexes with their acyclic counterparts. Finally, we address the question of anion binding selectivity by L(4+) and its L(1) (4+) and L(2) (4+) topological isomers. F(-) is too small for these three hosts, while I(-) is too big. According to free energy perturbation calculations, Cl(-) is preferred to Br(-), but somewhat more by L(1) (4+) than by L(4+).

Polycations. 4. Synthesis and antihydrophobic effect of polycationic strings

Two categories of polycationic “strings” have been synthesized and investigated for their effect on the aqueous solubility of hydrophobic organic compounds (benzene and 4-bromotoluene, the latter discussed here). Polycationic “strings” are compounds in which cationic sites (quaternary ammonium sites) are incorporated into the covalent structure along a linear chain with free-floating associated anions. The categories are: 1) defined length chains consisting of quaternized dabco units connected by intervening lengths of methylene groups, terminating with ω-alkanol units, and 2) α,ω-dimethylaminoalkane units quaternized with chain extending ω-alkanol units. The observed antihydrophobic effect depends on the total charge, the length of the charge-intervening linkages, and the terminating groups.

Reactions of polymer-supported ω-bromoalkylcarboxylates: formation of lactones versus oligomerization

The reactions of 4-bromobutyric acid, 5-bromopentanoic acid, 6-bromohexanoic acid, 8-bromo-octanoic acid, 11-bromoundecanoic acid and 12-methanesulfonyloxydodecanoic acid with the bicarbonate forms of various anion-exchange resins were investigated. Both macroporous resins and 2% crosslinked gel-type resins were used. The macroporous resins and some of the gel-type resins had quaternary ammonium sites; other gel-type resins had quarternary phosphonium sites. Various loadings of these sites were used. Ester formation could take place intramolecularly or intermolecularly and the ester products were analysed for lactone, diolide and oligoesters. 4-Bromobutyric acid and 5-bromopentanoic acid reacted with the macroporous polymer-supported bicarbonate to give the lactones in high yield. The remaining acids gave mainly oligomers with the macroporous resins and with the highly loaded gel-type resins. In the case of 11-bromoundecanoic acid it was shown that the oligomers had average degrees of polymerization of up to 27 and later work has shown that a substantial number of these are cyclic. As the loading of the bicarbonate on gel-type resins fell (< 33% of the phenyl residues bearing onium ion sites) site isolation became important and lactones and diolides were formed in significant yields. In all but one case, 8-bromo-octanoic acid, the yields were, however, consistent with the concentrations of the bicarbonate in the beads compared with the ‘effective molarities’ for such reactions. With 8-bromo-octanoic acid the yield of lactone obtained with a lightly loaded gel-type resin suggests considerable site isolation was achieved. There is evidence that as the chain lengths of the ω-bromo acids increases site isolation decreases due to ‘bridging’, i.e. the ability of the bromo end groups to reach over to the carboxylate groups on neighbouring sites. Substantial site isolation was achieved when 11-bromoundecanoic acid was reacted with a gel-type resin on which most of the 'onium salt sites were in the chloride form and only a small fraction were in the bicarbonate form. The reason why site isolation occurred in this case is unclear at present.

Durable nitrate-selective chemically modified field effect transistors based on new polysiloxane membranes

Polysiloxane copolymers with different amounts and types of substituents have been synthesized and characterized. Polar substituents determine the polarity and methacrylate groups allow cross-linking and covalent binding of electroactive species. These chemically well-defined homogeneous polymers have been applied as ion-selective membrane material in nitrate-selective field effect transistors (CHEMFETs). The selectivity of the CHEMFETs is influenced by the nature of the polar substituents in the polymer. The incorporation of methacrylate moieties in the polysiloxane allows covalent attachment of quaternary ammonium sites to the membrane matrix and this enlarges the durability of the sensor.

Segmental exchanges define 4-aminopyridine binding and the inner mouth of K + pores

4-Aminopyridine (4AP) blocks the intracellular mouth of voltage-gated K + channels. We identified critical regions for 4AP binding with chimeric channels in which segments of a low affinity clone (Kv2.1, IC 50 = 18 mM) were replaced with those of a high affinity clone (Kv3.1, IC 50 = 0.1 mM) 4AP sensitivity was not tranferred with the S5–S6 linker (pore or P region) Instead, a chimera of the cytoplasmic half of S6 increased block 20-fold, without affecting gating.A double chimera of the cytoplasmic halves of S5 and S6 fully transferred 4AP sensitivity. Because 4AP block was inhibited by tetrapentylammonium, we conclude that determinants of 4AP binding lie in the S6 segment that forms the cytoplasmic vestibule of the pore and that this site may overlap a quaternary ammonium site.

Polyampholytes for water treatment with magnetic particles

Amphoteric polymers which have cationic properties at acidic pH, but are neutral or anionic at alkaline pH, have been prepared and tested for water clarification and decolourization. The polymer is an adjunct to a magnetic iron oxide employed as the primary coagulant, which is recycled after alkaline treatment. A range of structures has been investigated, including copolymers of methacrylic acid with various quaternary ammonium monomers, terpolymers of these with methyl methacrylate as the third monomer, and polymers containing phenolic or amino acid moieties as well as quaternary ammonium sites. The last two groups of polymers were the most effective in enhancing water treatment performance, with concomitant facile regeneration behaviour.

Electrochemically PolymerizedN, N-Dimethylaniline Films Containing Tris-(Bathophenanthroline Disulfonato)Iron(II/III) Complexes

Abstract The electropolymerization of N, N-dimethylaniline (DMA) was carried out in an aqueous CF3COONa solution (pH 1.0) containing DMA in the presence of tris(bathophenanthroline disulfonato)iron(II), Fe(bphen)3 4-. Poly(N, N-dimethylanilinium trifluoroacetate) (PDMA) film was formed on electrode surfaces and, at the same time, Fe(bphen)3 4- ions were stably confined in the formed PDMA film by electrostatic interaction between them and the positively charged quaternary ammonium sites of the PDMA film. The PDMA-Fe(bphen)3 4-/3- film thus prepared displayed well-defined reversible electroactivity and electrochromic properties ascribable to those of the Fe(bphen)3 4-/3- couple confined in the film. The PDMA-Fe(bphen)3 4- film is red, and the PDMA-Fe(bphen)3 3- film is colorless. The response rate of the color change to a potential pulse was found to be correlated with the kinetic parameters characterizing the rate of the overall charge-transfer reaction at the PDMA-Fe(bphen)3 4-/3- film-coated electrode, t...

Anion inclusion without auxiliary hydrogen bonds: X-ray structure of the iodide cryptate of a macrotricyclic tetra-quaternary ammonium receptor

The X-ray Crystal and molecular structure of [I–L4+]3+ 3I–˙3MeCN·H2O, L = N4Me4(C6H12)6, shows on iodide anion to be encapsulated symmetrically into the spherical intramolecular cavity of the macrotricycle L4+ and held in place by the ectrostatic potential of the four quaternary ammonium sites arranged at the corners of an almost perfect tetrahedron; the N+⋯ I– distances average to 4.54(2)A whereas the distances between iodide and the carbon atoms of the [CH2]6 chains are of van der Waals type or longer.

Acid-Base and Chiroptical Properties of Partially Quaternized Optically Active Poly[thio-1-(N-(S)-s-butyl-N-methylaminomethyl)ethylene

Investigation was made of the effects of counterion exchange at quaternary ammonium sites and of protonation of residual tertiary amine groups on ORD and CD of partially quaternized poly[-thio-1-(N-(S)-s-butyl-N-methylaminomethyl)ethylene]s in water and in 80:20 v/v methanol–water mixture. Each repeating unit of this type of optically active copolymers bears two chiral centers, one in the main chain and one in the side-chain. The present study is limited to copolymers rendered optically active through side-chain chirality, the main-chain chiral centers being racemic. Compounds with 4 and 7% methylated tertiary amine groups (Q-P(TBMAE)RSS* 4 and 7 respectively) are considered. It is shown that deprotonated Q-P(TBMAE)RSS* 7 is slightly aggregated in water. The protonation of tertiary amine residues destabilizes the aggregates and then proceeds non-conventionally through a two-phase mechanism similar to a cooperative conformational transition. ORD and CD do not reflect the particular conformational behavior of Q-P(TBMAE)*. The acid-induced chiroptical property changes depend on the content of charged repeating units only. Comparison is made with Q-P(TDAE)* 17, an N,N-diethyl homologue of Q-P(TBMAE)*’s, whose optical activity is caused by main chain chiral centers only.

The Preparation of Merrifield‐Resins Through Total Esterification With Cesium Salts

AbstractThe reaction of chloromethylated polystyrene‐co‐1%‐divinylbenzene resin with the cesium salts of N‐protected amino acids proceeds fast and without side reactions to give N‐protected amino acyl resin esters free of quaternary ammonium sites or reactive chloride.

Molecular dynamics of acetylcholine and of choline

A Fourier Transform 13C and 14N NMR study of the behaviour of acetylcholine in solution has been performed. The local molecular motions and the corresponding activation parameters at each carbon have been obtained. The nitrogen-14 quadrupolar coupling constant, which reflects the electric properties of the quaternary ammonium site, has been determined. Results about the conformation of the molecule are also presented. No complexation with either AMP, ATP or CMP in the presence or absence of alcaline earth ions, could be detected.