Presence Of Tetrabutylammonium Ions Research Articles

Capillary Electrophoretic Characterization of Water-soluble Carbon Nanodots Formed from Glutamic Acid and Boric Acid under Microwave Irradiation.

Water-soluble carbon nanodots (CND) were synthesized under microwave irradiation from glutamic acid or glutamic acid-boric acid mixture. The CNDs were collected in an aqueous solution through size fractionation by centrifugal filtration. The CNDs thus prepared were subjected to characterization by capillary electrophoresis (CE). A peak signal of anionic substance was detected in the electropherogram, and it was found to be a major component of the CNDs. The effective electrophoretic mobility of the major component was almost identical over the pH range between 6.7 and 11.6, suggesting that the functional group of amine or boric acid moiety was not included in the CNDs. The effective electrophoretic mobility decreased at an acidic pH of less than 5, and it was suggested that carboxylate moiety was included in the CNDs. A signal of less-charged CNDs was also detected in the electropherogram, and the CNDs were characterized by a CE format of micellar electrokinetic chromatography. Two or four peaks were detected just after the electroosmotic flow; the less-charged CNDs were thus hydrophilic. The affinity interaction was also examined between the major anionic CNDs and a hydrophobic pairing cation. The peak signal of the major anionic CNDs broadened, and its theoretical number of plates decreased in the presence of tetrabutylammonium ion in the separation buffer. A small portion of the anionic CNDs were a little hydrophobic at different degrees, and their effective electrophoretic mobility decreased by the hydrophobic interaction, resulting in peak broadening of the anionic CNDs.

Vanillin production from native softwood lignin in the presence of tetrabutylammonium ion

Vanillin is one of the industrially important compounds that can be produced from lignin. This study presents production of vanillin and vanillic acid (oxidized form of vanillin) through aerobic oxidation of Japanese cedar (Cryptomeria japonica) at 120 °C for 72 h in aqueous alkali solutions with several Bu4N+ and OH− concentrations (1.25, 2.50, and 3.75 mol/L), where Bu4N+ is an enhancer of the vanillin formation reported in our previous study. The concentrations of Bu4N+ and OH− were adjusted by the additions of Bu4NCl and solid NaOH into the base medium Bu4NOH·30H2O, which forms 1.25 mol/L aqueous solution of Bu4NOH at the elevated temperature. Vanillin and vanillic acid were produced with the maximum yields of 21.0 and 1.7 wt% (lignin-base), respectively, at the 1.25 mol/L Bu4N+ and 3.75 mol/L OH− concentrations. This vanillin yield is close to that obtained by the alkaline nitrobenzene oxidation (26.5 wt%), indicating significantly high selectivity of our lignin degradation with Bu4N+ toward vanillin formation. We also proposed a novel Bu4NOH·30H2O-free reaction medium, where Bu4NOH·30H2O as the base medium were substituted with an aqueous solution of Bu4NCl and NaOH to avoid using expensive Bu4NOH·30H2O. The treatment of the Japanese cedar with this alternative medium exhibited the moderately decreased vanillin yield of 14.6 wt%, which is, however, much higher than the vanillin yield obtained with a simple 1.25 mol/L NaOH solution.

Voltammetric studies of microcrystalline C60 adhered to a carbon electrode surface and placed in contact with aqueous electrolyte containing potassium ions

The reduction of microcrystalline C60 fullerene, adhered at a carbon electrode and immersed in aqueous electrolyte, has been studied under various voltammetric conditions. This work reports mainly the voltammetric studies carried out principally in electrolyte containing potassium ions. Comparison of adherence techniques, such as solvent casting and mechanical transfer methods, are made to assess if the type of adhered techniques has any significant influence on the observed electrochemistry. The solvent casting method is found to produce three peaks in the potential for C600/n- redox couple as compared to a single and large peak produced when a mechanical transfer technique is employed. When the reduction potential of microcrystalline C60 in the presence of K+ is compared with other cations, such as Li, Na, Rb and Cs, it is observed that the shift of reduction potential follows the change in the hydration energy in the order Cs>Rb>K>Na>Li. In a mixed electrolyte study of CsCl/KCl, the reduction potential and peak shape of C600/n- redox couple during cyclic voltammetry is observed to change with concentration of the cations and the observed electrochemistry can be attributed to a cation-exchange mechanism. The reduction of C60 is irreversible in aqueous electrolyte containing alkaline cations as the re-oxidation process does not produce any observed electro-activity. Evidence of the formation of a passive coating of K nC60 fulleride, which does not appear to undergo dissolution is obtained under cyclic voltametric conditions. This coating remains electrochemically active in the presence of tetrabutylammonium ions in acetonitrile. Scan rate, chronocoulometric, and scanning electron microscopic studies provide evidence of the presence of a surface process involving solid–solid transformation.

Solvent Extraction of Anionic Silver(I) Thiocyanate Complex as Ion-Pairs with Tetrabutylammonium Ions into Chloroform and 4-Methyl-2-pentanone

Abstract Solvent extraction of silver(I) from aqueous 1 mol dm−3 Na(SCN, NO3) solutions, where the thiocyanate ion concentration was higher than 1 × 10−3 mol dm−3 and pH was 3, into chloroform and into 4-methyl-2-pentanone (MIBK) was studied in the presence of tetrabutylammonium ions (tba+) at 298 K. The extraction equilibria of the ion-pairs, tba+SCN− and tba+NO3− into these solvents were also determined. The experimental data were well explained by extraction of tba+Ag(SCN)2− into chloroform and both tba+Ag(SCN)2− and Na+Ag(SCN)2− into MIBK and by formation of Ag(SCN)n1−n, where n was 2 to 4 in the aqueous phase. More than half of the initial amount of tba+ in the aqueous phase was extracted as tba+SCN− and tba+NO3−. The analysis of the extraction data of silver(I) should be made by taking the decrease in the tba+ concentration due to these extractions into account. No dissociation of the ion-pairs was found in chloroform but the extracted ion-pairs were partially dissociated in MIBK. In the presence of 1 × 10−3 mol dm−3 tba+ in the initial aqueous phase, the extraction of silver(I) was much better into MIBK than into chloroform under otherwise identical conditions. The extraction and dissociation constants of the above species and the stability constants of the anionic thiocyanate complexes of silver(I) in the aqueous phase were calculated.

Solvent Extraction of Silver(I) as Anionic Metal Complexes with 2-Thenoyltrifluoroacetone and 4-Isopropyltropolone into Chloroform in the Presence of Tetrabutylammonium Ions.

The solvent extraction of silver(I) in aqueous 0.1 mol dm-3 sodium nitrate solutions with 2-thenoyltrifluoroacetone (Htta) and 4-isopropyltropolone (β-isopropyltropolone, Hipt) into chloroform was studied in the absence and presence of tetrabutylammonium ions (tba+), and the results were compared. Although extraction with Htta was poor, it was very much enhanced and nearly quantitative extraction was achieved by the addition of tba+. This was assumed to be due to the fact that the complex, Ag(tta), was hydrophilic due to its hydration, but tba+Ag(tta)2-, which was extracted in the presence of tba+, was very weakly hydrated and bulkier. Both Ag(ipt) and Ag(ipt)(Hipt) were extracted; extraction with Hipt was not very effective in the absence of tba+ By the addition of tba+, the anionic complex, tba+Ag(ipt)2, was also extracted, and nearly quantitative extraction was also achieved. Since the formation of this anionic complex is made by an exchange of ipt- with Hipt of the Ag(ipt)(Hipt) species, the enhancement of extraction was impaired by the dissociation of Hipt from the self-adduct.

Solvent Extraction of Thallium(I) with Chelating Extractants Coordinating through Oxygen Atoms

Abstract The solvent extraction of thallium(I) in aqueous 0.1 mol dm−3 sodium nitrate solutions with seven chelating extractants [(HA), 1-phenyl-1,3-butanedione (Hbza); 1,3-diphenyl-1,3-propanedione (Hdbm); 4,4,4-trifluoro-1-phenyl-1,3-butanedione (Hbfa); 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htta); 2-hydroxy-4-isopropyl-2,4,6-cycloheptatrien-1-one (Hipt); 5,7-dichloro-8-quinolinol (Hdcox); and 1,1,1-trifluoro-4-mercapto-4-(2-thienyl)-3-buten-2-one (Hstta)] into chloroform was studied in the absence and presence of tetrabutylammonium ions (tba+) or trioctylphosphine oxide (TOPO). The TlA type chelates were extracted, and, except for Hbza and Hdbm, tba+TlA2−-type ternary complexes were extracted. However, the extraction of adduct chelates with TOPO was not obtained. A comparison of the stability, liquid–liquid partition, and acceptability of a further ligand in the organic phase was made with TlA, AgA, and LiA when A− was 1,1,1-trifuluoro-3-(2-thienyl)-2,4-butanedionate ion (tta−) and the ligand was TOPO or tta−.

Double-layer dynamics in the adsorption of tetrabutylammonium ions at the mercury | water interface Part 4. The reduction of hexammine-cobalt(III) through tetrabutylammonium films

Abstract The reduction of hexamminecobalt(III) at the mercury-water interface is strongly affected by the presence of a condensed tetrabutylammonium film. When the anions present are fluoride and/or tetrafluoroborate, electron transfer through the film proceeds via an inner-sphere mechanism, i.e. the film must be opened so that hexamminecobalt(III) can make direct contact with the metal. In the presence of bromide anions, an outer-sphere pathway is indicated, probably involving bridging by bromide ions. Unusual current-time transients of the reduction of hexamminecobalt(III) in the presence of tetrabutylammonium ions are correlated with the kinetics of film formation.

Oxidation of Iron(II) during Solvent Extraction with Benzoyltrifluoroacetone into Carbon Tetrachloride in the Absence and Presence of Tetrabutylammonium Ion or Trioctylphosphine Oxide

Abstract The solvent extraction of iron(II) in aqueous 0.1 mol dm−3 sodium nitrate solutions containing ascorbic acid with benzoyltrifluoroacetone (Hbfa) into carbon tetrachloride was studied in the absence and presence of tetrabutylammonium ion (tba+) or trioctylphosphine oxide (TOPO). By the addition of tba+, the tba+Fe(bfa)3− species, and by the addition of TOPO, the Fe(bfa)2TOPOn (n = 1 or 2) species were extracted in addition to the Fe(bfa)2 species and the extraction was greatly enhanced. The iron(II) in the benzoyltrifluoroacetonate complex extracted in the organic phase was oxidized rather quickly and the rate of this oxidation was also studied. An addition of tba+ or TOPO to the system slowed down the oxidation reaction, and the reason for the effects of tba+ and TOPO on the rate of oxidation is discussed.

Solvent Extraction of Zinc(II) with 1-Naphthoic Acid into Chloroform in the Presence of Tetrabutylammonium Ions or Trioctylphosphine Oxide

The solvent extraction of zinc(II) in 0.1 mol dm−3 sodium chloride solutions with 1-naphthoic acid (HA) into chloroform was measured in the absence and presence of tetrabutylammonium ions (tba+) or trioctylphosphine oxide (TOPO). The extraction of zinc(II) with 1-naphthoic acid was rather poor and the extracted species were in the form of ZnA2 and ZnA2(HA)2 when the metal concentration in the organic phase was lower than 3×10−5 mol dm−3. However, the polymerized species, ZnnA2n(HA)m, were also extracted when zinc(Il) concentration in the organic phase was higher than that value. The addition of tba+ or TOPO enhanced the extraction of zinc(II) 1-naphthoate. This was explained in terms of the extraction of tba+ZnA3− or ZnA2TOPO species. Thus 1-naphthoic acid was found to be an effective extractant for zinc(II) only in the presence of bulky cations or solvating type extractants. We considered the reason why only the monomeric zinc(II) species of the ternary complex or the TOPO adduct was extracted.

Solvent Extraction of Several Divalent Metal Ions with Benzoyltrifluoroacetone and 2-Thenoyltrifluoroacetone into Chloroform in the Presence of Tetrabutylammonium Ions

Abstract The solvent extractions of manganese(II), iron(II), cobalt(II), nickel(II), copper(II), zinc(II), and cadmium(II) (M2+) in 0.1 mol dm−3 sodium nitrate solutions with benzoyltrifluoroacetone and 2-thenoyltrifluoroacetone (HA) into chloroform were studied in the absence and presence of tetrabutylammonium ions (tba+). The addition of tba+ enhanced the extraction, except that of copper(II). This enhancement could be explained in terms of the extraction of the ternary complex, MA3−tba+, in addition to the neutral complex, MA2. The data were treated on the basis of the formation equilibrium of the ternary complex from the neutral complex, MA2, with the extracted ion-pairs of the reagents, A−tba+, in the organic phase. It was concluded that the association constants of MnA2, FeA2, CoA2, NiA2, and CdA2 with the ion-pair, A−tba+, are not very much different from each other. However, that of ZnA2 is lower than those of the five divalent metal complexes. This trend is similar to that found among the adduct metal complexes of β-diketonates with trioctylphosphine oxide (TOPO) in synergistic extraction systems.

Solvent Extraction of Scandium(III) with Hexafluoroacetylacetone into Chloroform in the Absence and Presence of Tetrabutylammonium Ions or Trioctylphosphine Oxide

Abstract The anionic chelate of scandium(III) with hexafluoroacetylacetone (Hhfa) was extracted into chloroform in the presence of the tetrabutylammonium ion (tba+), though such an anionic chelate was not extracted when the chelating extractant was 2-thenoyltrifluoroacetone (Htta). The extraction was also studied in the same systems in the presence of trioctylphosphine oxide (TOPO); the extraction of the anionic complex, Sc(hfa)4−tba+, was compared with that of the adducts with TOPO, Sc(hfa)3(TOPO)n.

Solvent Extraction of Lanthanum(III), Europium(III), and Lutetium(III) with 5,7-Dichloro-8-quinolinol into Chloroform in the Absence and Presence of Tetrabutylammonium Ions or Trioctylphosphine Oxide

Abstract The solvent extractions of lanthanum(III), europium(III), and lutetium(III) (M3+) in 0.1 mol dm−3 sodium nitrate solutions with 5,7-dichloro-8-quinolinol(HA) into chloroform were studied in both the absence and presence of tetrabutylammonium ions (tba+) or trioctylphosphine oxide (TOPO). In the absence of tba+ or TOPO, the extracted species were the MA3 and MA3HA (self-adduct), though MA4−tba+ was found when tba+ was added; MA3TOPO and MA3(TOPO)2 were found when TOPO was added in addition to the above mentioned two species. The anionic complex or TOPO adducts greatly enhanced the extraction. The data were statistically analyzed and the equilibrium constants for the extraction of these species, as well as the constants for the association of the HA, the A−tba+, or the TOPO on the MA3 in the organic phase, were determined. The extraction of the MA3 is better in the order LaA3 < EuA3 < LuA3. Although the values of the association constant of the HA or the TOPO on the MA3 are rather similar for the three metal chelates, the constants for A−tba+ are larger in the same order as mentioned above. Thus, the separation of these three metal ions by solvent extraction with this chelating extractant is not much affected by the addition of TOPO, but is greatly improved by the addition of tba+.

Solvent Extraction of Alkaline Earth Ions with Benzoyltrifluoroacetone into Carbon Tetrachloride in the Absence and Presence of Tetrabutylammonium Ion or Trioctylphosphine Oxide

Abstract The solvent extraction of Mg2+, Ca2+, Sr2+, and Ba2+ (M2+) in aqueous 0.1 mol dm−3 sodium nitrate solutions with benzoyltrifluoroacetone (Hbfa) in carbon tetrachloride was studied in both the absence and presence of tetrabutylammonium ion (tba+) or trioctylphosphine oxide (TOPO). It was found that not only the M(bfa)2 species, but also the tba+M(bfa)3− or the M(bfa)2(TOPO)n species (n is 1 to 3), were extracted by the addition of tba+ or TOPO, and that the extraction was very much enhanced. The equilibria for the extractions were treated as the over-all equilibrium of (i) extraction of the M(bfa)2 chelate and (ii) the association of the ion-pair of the reagents, tba+bfa−, or the TOPO molecules with the chelate in the organic phase. The separation of these four metal ions was improved by the addition of tba+. This was due to the fact that the chelates of smaller M2+ associated with the tba+bfa− better than those of larger M2+ in the organic phase.

Solvent Extraction of Europium(III) with 1-Naphthoic Acid into Chloroform in the Absence and Presence of Tetrabutylammonium Ions or Trioctylphosphine Oxide

Abstract The solvent extraction of europium(III) in 0.1 mol dm−3 sodium nitrate solutions with 1-naphthoic acid (HA) into chloroform was studied in the absence and presence of tetrabutylammonium ions (tba+) or trioctylphosphine oxide (TOPO). In the absence of tba+ and TOPO the distribution ratio of europium(III) with 0.1 mol dm−3 1-naphthoic acid was higher when the initial concentration of the metal was higher under otherwise identical conditions. This could be explained in terms of the extraction of a polynuclear species, Eu2A6(HA)2, in addition to a mononuclear species, EuA3HA. Furthermore, by the addition of tba+ or TOPO, the extraction of europium(III) was greatly enhanced. This could be explained in terms of the extraction of the ternary complex, EuA4−tba+, or the adducts, EuA3TOPO and EuA3(TOPO)2, like that found in the extraction of this metal ion with β-diketones. In these systems the extracted anionic complex with tba+ or the adducts with TOPO were only mononuclear, even under conditions in which the polynuclear species were extracted in the absence of these.

Oxidation of Cerium(III) during Solvent Extraction with Benzoyltrifluoroacetone into Carbon Tetrachloride in the Absence and Presence of Tetrabutylammonium Ions

Cerium(III) in aqueous 0.1mol dm-3 sodium nitrate solutions was extracted with benzoyltrifluoroacetone (Hbfa) into carbon tetrachloride in the absence and presence of tetrabutylammonium (tba+). In the absence of tba+, only the Ce(bfa)3 was extracted; in its presence, however, not only was the ternary complex (Ce(bfa)4-tba+) also extracted, and the extraction was much better. When the two-phase agitation was continued, the organic phase gradually changed from colorless to brown in the absence of tba+ due to the oxidation of the metal ions in the complex in the organic phase to the cerium(IV). However, in the presence of tba+, the organic phase remained colorless for a long time and, thus, oxidation of the cerium(III) was negligible. The rate of oxidation of cerium(III) in the Ce(bfa)3 complex in carbon tetrachloride to the cerium(IV) by forming the Ce(bfa)4 complex was measured by spectrophotometry. The rate of this oxidation was found not to be affected by the ligand concentration.

Separation factor of lanthanoids by solvent extraction of their ternary complexes

The solvent extraction of praseodymium (III) and neodymium (III) (denoted by M 3+) with 2-thenoyltrifluoroacetone (Htta) into carbon tetrachloride was studied in the absence and presence of tetrabutylammonium ions (tba +). The extraction with Htta was greatly enhanced by the addition of tba +, and this fact was explained in terms of the formation of a ternary complex, M(tta) 4 −tba +. The neutral metal chelate was extracted into the organic phase and associated with ion pairs of the reagents, tta −tba +, in the organic phase. It was concluded that the degree of association of Pr(tta) 3 with tta −tba + (the ion pair) is slightly greater than that of Nd(tta) 3.

Effect of a Solvent on the Extraction of the Europium(III) 2-Thenoyltrifluoroacetonate Anionic Complex as Ion-Pairs with Tetrabutylammonium Ions

Abstract The solvent extraction of europium(III) in aqueous 0.1 mol dm−3 sodium nitrate or sodium chloride solutions with 2-thenoyltrifluoroacetone (Htta) into chloroform, toluene, and 4-methyl-2-pentanone (MIBK) was studied in both the absence and presence of tetrabutylammonium ions (tba+); the results were compared with those into carbon tetrachloride. When the diluent was chloroform or toluene, the extraction was greatly enhanced by the addition of tba+, just as with carbon tetrachloride. This could be explained in terms of the extraction of the Eu(tta)4−tba+ species, in addition to the Eu(tta)3 species. However, this did not occur in the MIBK system, and was explained in terms of stable solvates with MIBK, which interfere with the addition of tta−tba+ ion-pairs on the Eu(tta)3 species. The enhancement due to the extraction of Eu(tta)4−tba+ was not very much different from that in the other solvent systems. This could be explained by assuming that although the amount of tta−tba+ in the organic phase was smaller in the order chloroform > toluene > carbon tetrachloride, the degree of association of this ion-pair with the Eu(tta)3 in the organic phase was larger in the inverse order, and that these two opposite tendencies canceled each other out. The results were compared with the synergistic enhancement of the extraction of europium(III) with Htta by organophilic neutral ligands, such as tributylphosphate.

Solvent Extraction of Anionic Chelate Complexes of Lanthanum(III), Europium(III), Lutetium(III), Scandium(III), and Indium(III) with 2-Thenoyltrifluoroacetone as Ion-Pairs with Tetrabutylammonium Ions

Abstract The solvent extraction of lanthanum(III), europium(III), lutetium(III), scandium(III), and indium(III) in 0.1 mol dm−3 sodium nitrate solutions with 2-thenoyltrifluoroacetone (Htta) in the absence and presence of tetrabutylammonium ions (tba+) into carbon tetrachloride was measured. The extraction of lanthanum(III), europium(III), and lutetium(III) was greatly enhanced by the addition of tba+; this could be explained in terms of the extraction of a ternary complex, M(tta)4−tba+. However, the extractions of scandium(III) and indium(III) were nearly the same when tba+ was added. The data were treated on the basis of the formation equilibrium of the ternary complex from the neutral chelate, M(tta)3, with the extracted ion-pairs of the reagents, tta−tba+, in the organic phase. It was concluded that the degree of association of M(tta)3 with the ion-pair, tta−tba+, is greater in the order La(tta)3 ≈ Eu(tta)3 > Lu(tta)3, or that the stability of the ternary complex in the organic phase is higher in the order La(tta)4−tba+ ≈ Eu(tta)4−tba+ > Lu(tta)4−tba+. This is similar to those of adduct metal chelates of Htta with tributylphosphate (TBP) in synergistic extraction systems.

Solvent Extraction of Europium(III) with Benzoylacetone and Benzoyltrifluoroacetone into Carbon Tetrachloride in the Absence and Presence of Tetrabutylammonium Ions

Abstract The solvent extraction of europium(III) in 0.1 mol dm−3 sodium nitrate solutions with benzoylacetone (Hbza) or benzoyltrifluoroacetone (Hbfa) in carbon tetrachloride was measured in the absence and presence of tetrabutylammonium ions (tba+). Although extraction with Hbfa occurred at lower pH than with Hbza, the extraction measured as a function of the β-diketonate ion concentration in the aqueous phase was rather similar. It was also found that extraction with Hbfa was greatly enhanced by the addition of tba+, the effect, however, was negligible with Hbza. The data were analyzed from the stand point that the neutral metal chelate, Eu(bfa)3, was extacted into the organic phase and associated with ion-pairs of the reagents, bfa−tba+, in this phase. It was also found that though extraction of ion-pairs of bfa− tba+ occurred, that of bza−tba+ was negligible. Thus, the reason for the negligible extraction of the ternary complex, Eu (bza)4− tba+, was explained in terms of the negligible extraction of the bza−tba+, which might associate with Eu(bza)3 in the organic phase.

The effect of tetrabutylammonium ion on chicken brain acetylcholinesterase activity in vitro.

The effect of tetrabutylammonium ion on chicken brain acetylcholinesterase activity was investigated. Tetrabutylammonium ion (1-4mM) reversibly inhibited acetylcholinesterase activity of chicken brain (34-73%) in a concentration dependent manner, the IC50 being about 1.1mM. A Lineweaver-Burk plot, as well as a Dixon plot, indicated that the nature of inhibition is noncompetitive with a Km value of 0.134mM and a Ki value of 1.58mM at 37 degrees C. An Arrhenius plot showed that the transition temperature is significantly reduced in the presence of tetrabutylammonium ion.