Synthesis and properties of ambient temperature molten salts based on the quaternary ammonium ion

The synthesis of 16 tetraalkyl ammonium bis(trifluoromethane sulfonyl) imide salts, (C_nH_2n+1)₄ +N -N (SO₂CF₃)₂ (n = 1, 2, 3, 4),  (C₂H₅)₂(i-C₃H₇)₂ +N -N(SO₂CF₃)₂, (C₂H₅)(CH₃)(i-C₃H₇)₂+N-N(SO₂CF₃)₂, (n-C₇H₁₅)(C₂H₅)i-C₃H₇)₂+N-N(SO₂CF₃)₂ and (C_nH_2n+1)(C_mH_2m+1)₃+N-N(SO₂CF₃)₂ (n = 6,7,8; m = 1, 2, 4) are reported in this paper. Trends in properties of these salts are discussed. The symmetrical tetraalkyl ammonium salts with the bis(trifluoromethyl sulfonyl) imide anion exhibited a lower melting point than that of corresponding ammonium halides. The salts with low symmetry ammonium cations were found to be of generally lower melting point, and many were stable liquids at room temperature. Several of these did not crystallize during cooling below room temperature and exhibited glass transition temperatures in the region of −60 °C∼−80 °C. A comparison of properties between the ammonium imide salts and corresponding trifluoromethane sulfonates is also presented.

Novel alkaline polymer electrolytes based on tetramethyl ammonium hydroxide

In this work, novel alkaline solid polymer electrolytes (SPEs) with tetramethyl ammonium hydroxide (Me₄NOH·xH₂O) have been developed, without addition of any volatile solvent. It was found that some polymers such as poly(sodium acrylate) had good compatibility with Me₄NOH·xH₂O. The polymer-Me₄NOH·xH₂O electrolytes thus prepared in this work appeared to have improved mechanical properties as compared with the pure hydroxide and remained highly conductive in the solid state (10² S cm⁻¹ at ~40 °C). The thermal properties of the alkaline SPEs and the dependence of conductivity on composition and temperature are presented, and the relationships between properties and composition as well as conductivity mechanism for these new systems are discussed.

Studies on the properties and the thermal decomposition kinetics of natural rubber prepared with calcium chloride

To evaluate calcium chloride coagulation technology, two kinds of raw natural rubber samples were produced by calcium chloride and acetic acid respectively. Plasticity retention index (PRI), thermal degradation process, thermal degradation kinetics and differential thermal analysis of two samples studied. Furthermore, thermal degradation activation energy, pre-exponential factor and rate constant were calculated. The results show that natural rubber produced by calcium chloride possesses good mechanical property and poor thermo-stability in comparison to natural rubber produced by acetic acid.

Wool powders used as sorbents to remove Co2+ ions from aqueous solution

The Co2+ sorption of two wool powders was investigated using its radioisotope 57Co (T1/2=271.8 days and γ=122.1 and 136.5 keV) as a tracer. The effects of the type of buffer, the pH value, the contact time and the initial concentration of Co2+ on the sorption behaviour of wool powders were studied. The Co2+ releasing ability of wool powders and the re-use of wool powders to sorb Co2+ were also examined. The optimum sorption of Co2+ by the powders occurred at pH 8 in phosphate buffer and pH 10 in ammonium sulphate buffer. Fourier-transform infrared spectroscopy (FTIR) was used to study the changes in chemical structure of the wool after exposure to both buffer solutions. Compared to the untreated wool fibre, the fine wool powders showed rapid sorption rates and high sorption capacities for Co2+. Co2+ ions were recovered after exposing the Co2+ loaded wool to HCl (0.1 M) and buffer at pH 3 (glycine/sodium chloride). After releasing Co2+ ions from wool powders, the efficiency of wool powders re-used to sorb Co2+ was 80% of that of the fresh wool powders. It is concluded from this study that wool powder can be used as an efficient sorbent to remove and release Co2+ from solution.

Surface-Enhanced Infrared Spectra of Manganese (III) Tetraphenylporphine Chloride Physisorbed on Gold Island Films

Surface-enhanced infrared absorption (SEIRA) spectra of manganese (III) tetraphenylporphine chloride (Mn(TPP)Cl) on metal island films were measured in transmission mode. Dependences of the enhancement factor of SEIRA on both the sample quantity and the type of evaporated metal were investigated by subsequently increasing the amount of Mn(TPP)Cl on gold and silver substrates. The enhancement increases nonlinearly with the amount of sample and varies slightly with the thickness of metal islands. In particular, the SEIRA transmission method presents an anomalous spectral enhancement by a factor of 579, with substantial spectral shifts, observed only for the physisorbed Mn(TPP)Cl that remained on a 3-nm-thick gold film after immersion of the substrates into acetone. A charge-transfer (CT) interaction between the porphyrinic Mn and gold islands is therefore proposed as an additional factor in the SEIRA mechanism of the porphyrin system. The number of remaining porphyrin molecules was estimated by calibration-based fluorescence spectroscopy to be 2.36×1013 molecules (i.e., ~2.910-11 mol/cm2) for a 3-nm-thick gold film, suggesting that the physisorbed molecules distributed very loosely on the metal island surface as a result of the weak van der Waals interactions. Fluorescence microscopy revealed the formation of microcrystalline porphyrin aggregates during the consecutive increase in sample solution. However, the immersion likely redistributed the porphyrin to be directly attached on the gold surface, as evidenced by an absence of porphyrinic microcrystals and the observed SEIRA enhancement. The distinctive red shift in the UV-visible spectra and the SEIRA-enhanced peaks indicate the presence of a preferred orientation in the form of the porphyrin ring inclined with respect to the gold surface.

Arg1098 is critical for the chloride dependence of human angiotensin I-converting enzyme C-domain catalytic activity

Angiotensin (Ang) I-converting enzyme (ACE) is a Zn²+ metalloprotease with two homologous catalytic domains. Both the N- and C-terminal domains are peptidyl dipeptidases. Hydrolysis by ACE of its decapeptide substrate Ang I is increased by Cl−, but the molecular mechanism of this regulation is unclear. A search for single substitutions to Gln among all conserved basic residues (Lys/Arg) in human ACE C-domain identified R1098Q as the sole mutant that lacked Cl− dependence. Cl−dependence is also lost when the equivalent Arg in the N-domain, Arg⁵⁰⁰, is substituted with Gln. The Arg¹⁰⁹⁸ to Lys substitution reduced Cl− binding affinity by ∼100-fold. In the absence of Cl−, substrate binding affinity (1/K m) of and catalytic efficiency (k cat/K m) for Ang I hydrolysis are increased 6.9- and 32-fold, respectively, by the Arg¹⁰⁹⁸ to Gln substitution, and are similar (<2-fold difference) to the respective wild-type C-domain catalytic constants in the presence of optimal [Cl−]. The Arg¹⁰⁹⁸ to Gln substitution also eliminates Cl− dependence for hydrolysis of tetrapeptide substrates, but activity toward these substrates is similar to that of the wild-type C-domain in the absence of Cl−. These findings indicate that: 1) Arg¹⁰⁹⁸ is a critical residue of the C-domain Cl−-binding site and 2) a basic side chain is necessary for Cl− dependence. For tetrapeptide substrates, the inability of R1098Q to recreate the high affinity state generated by the Cl−-C-domain interaction suggests that substrate interactions with the enzyme-bound Cl− are much more important for the hydrolysis of short substrates than for Ang I. Since Cl− concentrations are saturating under physiological conditions and Arg¹⁰⁹⁸ is not critical for Ang I hydrolysis, we speculate that the evolutionary pressure for the maintenance of the Cl−-binding site is its ability to allow cleavage of short cognate peptide substrates at high catalytic efficiencies.

Nanofiltration for the possible reuse of water and recovery of sodium chloride salt from textile effluent

During the reactive dyeing of cotton, salts such as sodium chloride (NaCI) are placed in a dyebath to aid the exhaustion of various dyes onto the fabric while bases are added to raise the pH from around neutral to pH 11 to achieve fixation. Afterwards, the used dyebath solution, called dyebath spent liquor, is discharged with almost all the salts and bases added as well as unfixed dyes. Consequently, many raw materials are lost in the waste stream ending up in the environment as pollutants. In this study possibilities of reusing the water and salts of dyebaths were investigated using a nanofiltration membrane. When the NaCI concentration in the spent liquor was increased from 10 to 80 g/L, the NaC1 rejection by the membrane was found to decrease initially; however, the NaC1 rejection increased over time, which was not expected. The aggregation of dye was also studied and found to decrease in the concentrate when the salt concentration was increased. This information is useful for the textile industry in evaluating the treated water quality for the purpose of reuse.

Measurement of surface forces between mica sheets immersed in aqueous quaternary ammonium ion solutions

Forces between mica surfaces immersed in Me4NBr, Pr4NBr, and Pe4NBr solutions over a wide concentration range are reported (Me = methyl, Pr = propyl, Pe = pentyl). In each case the cation adsorbs quite strongly onto the negatively charged mica surface and determines the double-layer potential. However, this strong adsorption does not cause complete neutralization of the negative lattice charge apparently because of packing constraints due to the large size of these ions. Adsorption of Me4N+ ions gives rise to a short-range (<2 nm) repulsive force similar to that previously observed between bilayers of CTAB and may be due to the residual hydration of these ions. The large rations also, unexpectedly, give rise to short-range repulsive forces but of a somewhat different nature. In this case, the repulsive forces can be explained by assuming that the large adsorbed ions shift the plane of charge a distance of one ion diameter from the mica surface. At all but very high concentrations these larger ions could be displaced from the mica surfaces on forcing them together. No evidence of any “hydrophobic attraction” was observed between surfaces containing these adsorbed ions. Previous studies on coagulation are discussed in the light of our results.

Protic ionic liquids based on phosphonium cations : comparison with ammonium analogues

Novel protic ionic liquids (PILs) based on a tributyl phosphonium cation have been synthesised and characterised, revealing that the phosphonium based ILs show high thermal stability, high ionic conductivity and facile proton reduction compared to the corresponding ammonium based ILs.

The determination and characterisation of 2-naphthyloxycarbonyl chloride derivatised biogenic amines in pet foods

The need to monitor biogenic amines levels is essential for many areas of the food industry for two main reasons: the caustic nature and potential toxicity of these amines, and the potential to use amine levels as markers for freshness and quality in foodstuffs. Optimised analysis conditions used for the determination of biogenic amines derivatised with 2-napthyloxycarbonyl chloride has been applied to different pet food samples to assess the effectiveness of this method for complex sample matrices. Further to this, the use of high-resolution mass spectrometry has enabled the previously unconfirmed derivatised form of seven biogenic amines to be established. The derivatised forms identified include as mono substituted (tryptamine and histamine), bisubstituted (putrescine, cadaverine and tyramine), trisubstituted (spermidine) and tetrasubstituted (spermine). The methodology of biogenic amine determination was performed successfully to a range of pet food products highlighting the applicability to a variety of complex sample matrices.