bluuebunny/crossref_metadata_2025 huggingface dataset:
Platinum(II) complexes of the tridentate thioether ligands RS(CH2)3S(CH2)3SR (R = Et, iPr, Ph). Structures of [PtCl (iPrS(CH2)3S(CH2)3SiPr)][BF4], [PtI(PhS(CH2)3S(CH2)2SPh)][BF4], and [Pt(PPh3)(iPrS(CH2)3S(CH2)3SiPr)][BF4]2•CH2Cl2
Authors: Loeb Stephen J. , Mansfield James R.
Published: May 2006

The tridentate thioether ligands RS(CH2)3S(CH2)3SR (L1, R = Et; L2, R = iPr, L3, R = Ph) were synthesized by nucleophilic addition of thiolate, SR−, to the ditosylate TsO(CH2)3S(CH2)3OTs. The complexes [PtX(Ln)][BF4] were prepared by displacement of 1,5-COD from [PtX2(1,5-COD)] (X = Cl, I) in the presence of one equivalent of AgBF4 and one equivalent of thioether ligand. [PtCl(L2)][BF4] crystallized in the monoclinic space group P21/c with a = 10.409(6), b = 14.180(4), c = 13.726(8) Å, β = 104.49(4)°, V = 1961(2) Å3 and Z = 4. The structure refined toR = 5.62% and Rw = 6.86% for 2121 reflections with F02 > 3σ(Fo2). [PtI(L3)][BF4] crystallized in the monoclinic space group P21/n with a = 13.415(4), b = 12.350(5), c = 14.316(5) Å, β = 107.48(3)°, V = 2262(1) Å3 and Z = 4. The structure refined to R = 4.85% and Rw = 6.33% for 2168 reflections with Fo2 > 3σ(Fo2). In both compounds, the thioether ligand acts as a tridentate chelator occupying three of the four sites of the square-planar Pt(II) complex. Variable temperature 13C{1H} NMR verified that there are three possible stereoisomers for these complexes resulting from inversion at sulphur: meso-A, meso-B, and racemic. Thermodynamic parameters were calculated for the interconversion among isomers of [PtCl(L2)][BF4] by a full line-shape analysis. Removal of chloride ligand from [PtCl(L2)][BF4] with Ag+ in the presence of PPh3 yielded the phosphine adduct [Pt(PPh3)(L2)][BF4]2, which crystallized in the triclinic space group [Formula: see text] with a = 13.266(3), b = 11.315(2), c = 13.970(2) Å, α = 106.04(2)°, β = 84.95(2)°, γ = 86.56(2)°, V = 1999.7(7) Å3 and Z = 2. The structure refined to R = 4.22% and Rw = 5.38% for 4493 reflections with Fo2 > 3σ(Fo2). Unlike the two halide complex structures, which crystallized in the meso-B form, [Pt(PPh3)(L2][BF4]2 crystallized in the racemic form. Key words: tridentate thioether ligand, crystal structure, platinum(II) halide, dynamic NMR spectroscopy.
Intramolecular Diels–Alder reactions of 2H-thiopyran dienes
Authors: Ward Dale E. , Nixey Thomas E. , Gai Yuanzhu , Hrapchak Matthew J. , Abaee M. Saeed
Published: May 2006

A systematic survey of IMDA reactions of 4-[tris(2-methylethyl)silyl]oxy-2H-thiopyran derivatives with potential dienophiles tethered at the C-2, C-3, C-5, and C-6 positions is presented. Cycloaddition was not observed with a C3 or C4 tether and an unactivated terminal olefin as dienophile. IMDA adducts could be obtained when dienophiles activated by a carbomethoxy group were employed. Compounds having the activated dienophile attached via a C3 tether to C-2 of the 2H-thiopyran gave adducts with high stereoselectivity. Substrates having the dienophile attached to C-3 with a C3 or C4 tether cyclized readily. With an (E)-enoate as the dienophile, the stereoselectivity was poor (endo:exo = 1.1–2.5:1) and essentially independent of reaction conditions (i.e., thermal vs. Lewis acid mediated). With the(Z)-enoate, a 7:1 mixture of endo:exo IMDA adducts was obtained under thermal conditions; with Lewis acid catalysis, isomerization of the dienophile was competitive with cycloaddition. Type II IMDA adducts were not observed with C-5 tethered substrates. Compounds having the dienophile attached to C-6 via a C3 or a five-atom tether also failed to give IMDA adducts. No evidence for isomerization of the 2H-thiopyran dienes by [1,5] sigmatropic rearrangement was observed. The endo adducts from IMDA reactions of the C-3 tethered substrates can be desulfurized to obtain synthetically useful trans-fused hydrindans and decalins with angular methyl groups. Key words: intramolecular Diels–Alder, 2H-thiopyran, cis-substituted 1,3-diene surrogate, trans-octahydro-3a-methyl-1H-indene derivatives, trans-decahydro-4a-methylnapthalene derivatives.
Hydrogen isotope fractionation between methanol and diphenylphosphine or dimethylphosphine in the gas phase and in aprotic solvents
Authors: Wawer Andrzej , Szydtlowski Jerzy
Published: May 2006

D/H fractionation factors between MeOH and Ph2PH in dilute solutions of tetrachloroethylene, benzene, tetrahydrofuran, pyridine, and acetonitrile and T/H fractionation factors between MeOH and Me2PH vapors were measured. The experimental results agree very well with values calculated from the statistical theory of isotope effects formulated by Bigeleisen and Mayer. There are correlations between observed fractionation factors and solvent polarity, and the interaction energy of methanol with the given solvent. Another correlation has been found between enthalpy of the exchange reactions and the interaction energy between methanol and the given solvent. Key words: isotope effects, fractionation factor, diphenylphosphine, methanol.
(Alkylthio)- and (phenylthio)methoxycarbenes from oxadiazolines
Authors: Er Hui-Teng , Pole David L. , Warkentin John
Published: May 2006

Four 2-methoxy-5,5-dimethyl-Δ3-1,3,4-oxadiazolines bearing an alkylthio or arylthio group at C2 were prepared. The oxadiazolines undergo thermolysis at 60–80 °C in solution to afford the corresponding oxythiocarbene intermediates. In the absence of carbene traps, dimers of the carbenes were formed. The carbenes were trapped with ethyl crotonate, with dichloromaleic anhydride, with dimethyl acetylenedicarboxylate, and with phenyl isocyanate. Phenyl isocyanate traps methoxy(methylthio)carbene to form two types of adducts, both fundamentally different from the product obtained from reaction of dimethoxycarbene with phenyl isocyanate. All of the adducts have structures consistent with nucleophilic behaviour of the carbenes. Key words: oxythiocarbene, oxadiazoline, thermolysis, nucleophilic.
Structural diversity in thallium chemistry: structures of four chlorothallate(III) salts including a novel compound containing three geometrically different anions
Authors: James Margaret Ann , Clyburne Jason A.C. , Linden Anthony , James Bruce D. , Liesegang John , Zuzich Vilma
Published: May 2006

Four new thallium-containing salts with different alkyl ammonium cations have been prepared and characterized by X-ray crystallography: 1: bis(p-toluidinium) pentachlorothallate(III), [CH3C6H4NH3]2 [TlCl5], M = 597.9, monoclinic, P21/c, a = 7.515(2), b = 21.376(6), c = 12.769(2) Å, β = 92.13(2)°, V = 2050(1) Å3, Z = 4, Dcalc = 1.937 Mg m−3, µ = 8.512 mm−1, T = 293(1) K, R = 0.046; 2: 1,5-pentanediammonium pentachlorothallate(III), [NH3(CH2)5NH3] [TlCl5], M = 485.83, orthorhombic, P212121, a = 13.226(2), b = 13.595(2), c = 7.628(2) Å, V = 1371.6(3) Å3, Z = 4, Dcalc = 2.352 Mg m−3, µ = 12.84 mm−1, T = 173(1) K, R = 0.025; 3: pentakis(2-adamantaneammoniumn) bistetrachlorothallate(III) hexachlorothallate(III), [C10H18N]5 [TlCl4]2[TlCl6], M = 1870.75, monoclinic, P21a = 16.466(5), b = 25.985(2), c = 7.724(3) Å, β = 90.14(3)°, V = 3305(2) Å3, Z = 2, Dcalc = 1.880 Mg m−3, µ = 7.978 mm−1, T = 173(1) K, R = 0.056; 4: bis(piperazinium) decachlorodithallate(III) trihydrate, [NH2C4H8NH2]2 [Tl2Cl10]•3H2O, M = 993.62, monoclinic, C2/c, a = 14.154(3), b = 15.445(3), c = 13.228(3) Å, β = 114.44(1)°, V = 2632.7(9) Å3, Z = 4, Dcalc = 2.506 Mg m−3, µ = 13.39 mm−1, T = 173(1) K, R = 0.026. For most of the salts examined, formation of [TlCl5]2− is possible; however, no isolated [TlCl5]2− anions were observed. In most cases, high coordination numbers at thallium were observed (CN = 6), and these can be achieved via formation of anionic chains or through dimerization, giving [Tl2Cl10]4−. Of particular interest is the solid state structure of salt 3 in which there are three geometrically different chlorothallate ions. Extensive hydrogen-bonding networks are observed in each structure. Key words: thallium, thallium(III) chlorides, chlorothallate, hydrogen bonding, alkyl ammonium cations.
An estimate of the spin–spin coupling constant, 1J(1H,13C), in gaseous benzene
Authors: Schaefer Ted , Bernard Guy M. , Hruska Frank E.
Published: May 2006

An excellent linear correlation (r = 0.9999) exists between the spin–spin coupling constants 1J(1H,13C), in benzene dissolved in four solvents (R. Laatikainen et al. J. Am. Chem. Soc. 117, 11006 (1995)) and Ando's solvation dielectric function, ε/(ε – 1). The solvents are cyclohexane, carbon disulfide, pyridine, and acetone. 1J(1H,13C)for gaseous benzene is predicted to be 156.99(2) Hz at 300 K. Key words: spin–spin coupling constants, 1J(1H,13C) for benzene in the vapor phase; spin–spin coupling constants, solvent dielectric constant dependence of 1J(1H,13C) in benzene; benzene, estimate of 1J(1H,13C) in the vapor; nuclear magnetic resonance, estimate of 1J(1H,13C) in gaseous benzene.
Synthesis of glycosylated cationic porphyrins as potential agents in photodynamic therapy
Authors: Driaf Khalid , Granet Robert , krausz Pierre , Kaouadji Mourad , Verneuil Bernard , Thomasson François , Chulia Albert José , Spiro Marenglen , Biais Jean-Claude , Bolbach Gérard
Published: May 2006

Trisalkylpyridinium porphyrins substituted by one glycosyl (glucosyl, maltosyl, and lactosyl) moiety have been prepared in acceptable yields. These glycosylated cationic porphyrins have been synthesized from pyrrole condensed with 4-pyridinecarboxaldehyde, and suitable ortho- or para peracetylglycosyloxybenzaldehyde derivatives in refluxing propionic acid –Ac2O followed by action of alkyliodide in DMF. Deprotection of the glycosylated moieties led to a new class of representative glycosylated porphyrins. Key words: porphyrins, cationic, glycosylated; phototherapy, cancer.
Synthesis of 1-alkoxy-1,2,3,4-tetra-hydrocarbazoles by mercury(II) mediated heterocyclization of 2-cyclohex-2′-enyl-N-alkylanilines
Authors: Majumdar K. C. , Das U.
Published: May 2006

The title compounds 3(a–i) were synthesized in high yields by the mercury(II) mediated heterocyclization of 2-cyclohex-2′-enyl-N-alkylanilines 2(a–g), which in turn were obtained by the acid-catalyzed amino Claisen rearrangement of 3-N-alkylanilinocyclohexenes 1(a–g). Additional supporting evidence for the structure of product 3 was obtained from chemical transformations. Key words: 1-alkoxy tetrahydrocarbazole, mercury(II) mediated heterocyclization, amino Claisen rearrangement, 3-N-methylanilinocyclohexene.
Shape-similarity analysis of 20 stable conformations of neutral β-alanine
Authors: Heal Gerard A. , Walker P. Duane , Mezey Paul G. , Ramek Michael
Published: May 2006

The family of 20 stable conformations of neutral β-alanine are analyzed in terms of their shape similarities using the topological Shape Group Method, a general molecular shape analysis technique as applied to the three-dimensional electronic density. Molecular electron densities are calculated using the 6-31G** basis set, followed by the determination of the shape groups of local curvature patterns for the entire chemically relevant range of electron density contour surfaces. The results of the shape group analysis are represented by two-dimensional shape maps. Discretized grids of these maps generate numerical shape codes, and comparisons of these numerical codes serve as measures of shape similarity of the various conformers of β-alanine. This technique is based on direct comparisons of the intrinsic shape features of molecules and requires no superposition of molecules for comparisons. Mathematically well-defined and unbiased similarity measures are obtained by this non-visual, computer-based method, useful for the detection, quantification, and analysis of electronic charge distribution similarities. The family of 20 stable conformers of β-alanine serves as a test case for the application of the methodology for a large number of conformers, representing a level of complexity analogous to that of typical conformational problems in computer-aided drug design and the screening of potential drug molecules for shape similarity. Key words: similarity measures, shape groups, β-alanine, conformation analysis, molecular shape, electron density.
Differentiation of cerebroside isomers and study of fragmentation by liquid secondary ion mass spectrometry and mass spectrometry/mass spectrometry of selected derivatives
Authors: Perreault Hélène , Costello Catherine E.
Published: May 2006

The possibility of distinguishing two cerebroside isomers, whose structural variation is in the sugar rings, was investigated by liquid secondary ion mass spectrometry (LSIMS) and tandem mass spectrometry (MS/MS). In addition to the native materials, four types of derivatives of these cerebroside isomers were prepared and studied using these techniques. A first level of comparison between isomers consisted of seeking differences in the conventional LSIMS spectra. Native compounds, galactosyl and glucosyl ceramides, did not yield consistent and meaningful elements of comparison and a few nanomoles of material were required to produce significant spectra. Permethylated cerebrosides gave rise to abundant ceramide ions that do not reveal information about sugar structure; relative abundances of low-mass sugar-related ions allowed isomeric discrimination to a limited extent. Peracetylated and perbenzoylated derivatives of both cerebrosides yielded several sugar-related ions whose relative abundances in the spectra varied systematically between species and allowed distinction of glucosyl- from galacto-cerebrosides. At a second level of comparison, collision-induced dissociation (CID) MS/MS spectra of selected ions containing the hexosyl residues and observed in the LSIMS spectra were recorded to study the extent and pathways of fragmentation for each isomer. Native and permethylated compounds led to disappointing results; on the other hand, peracetylated and perbenzoylated derivatives yielded informative spectra where isomeric differentiation was possible, mostly owing to the production of carbohydrate-related product ions, whereas native and permethylated compounds only produced ceramide-related ions upon CID MS/MS. Key words: glycosphingolipids, cerebrosides, derivatization, mass spectrometry, MS/MS, LSIMS.
Aqueous nonelectrolyte solutions. Part XIV. D-ice and D-hydrate freezing points of deuterium oxide – ethylene oxide solutions and the formula of congruent ethylene oxide D-hydrate
Authors: Glew David N. , Rath Norman S.
Published: May 2006

D-ice freezing temperatures and D-hydrate formation temperatures have been measured by the dynamic cooling method for deuterium oxide – ethylene oxide (EO) solutions containing from 0 to 95.5 mol% EO. The D-ice and the congruent EO D-hydrate freezing temperatures exhibited standard errors (SEs) on a single measurement of 0.004 °C and 0.017 °C, respectively. The D-ice–D-hydrate eutectic temperature was observed at 1.500 °C with standard error (SE) 0.002 °C and at composition 2.207 mol% EO with SE 0.010 mol% EO. The congruent EO D-hydrate was found to freeze at 13.242 °C with SE 0.007 °C and at composition 12.60 mol% EO with SE 0.07 mol% EO. The formula of the congruent EO D-hydrate was EO•6.93D2O with SE 0.045 mol D2O/mol EO. Only one type of D-hydrate was found over the whole composition range down to −23 °C: the shoulder of the D-hydrate freezing curve above 40 mol% EO resulted from the high activity coefficients of dilute deuterium oxide in concentrated EO solutions. Equations and best values for the D-ice freezing temperatures and the D-hydrate formation temperatures together with their SEs were evaluated by the method of least squares. Properties of EO D-hydrate are compared with those of EO hydrate. Key words: clathrate D-hydrate of ethylene oxide, freezing of deuterium oxide – ethylene oxide, ethylene oxide D-hydrate, formula of ethylene oxide D-hydrate.
Evidence for an intramolecular transition metal Arbuzov reaction
Authors: Chen Zhao , Jablonski Chet , Bridson John
Published: May 2006

Reaction of [CpCo(C3F7)(I)(L)], (L = PPh2Me (1a), PPhMe2(1b), PMe3(1c), and PPh(OMe)2(2)), with PPh(OMe)2affords diastereomeric Co-and P-chiral metallophosphinates CpCo(C3F7)(L)(P(O)Ph(OMe)), 4a,b,c and 6, respectively. The solid state structure and relative configuration of the lower Rfdiastereomeric phosphinate CpCo(C3F7)(PPh(OMe)2)(P(O)Ph(OMe)), 6-2, was determined by X-ray diffraction. RR;SS-6-2 crystallizes in the triclinia system with space group [Formula: see text](no. 2), with a = 12.928(4) Å, b = 14.683(4) Å, c = 7.666(2) Å, a = 103.50(2)°, β = 101.31(3)°, γ = 109.50(2)°, V = 1272.8(7) Å3, Z = 2, and R = 0.036 (Rw = 0.030) for 2867 reflections with I > 3.00σ(I). CpCo(C3F7)(I)(PPh(OMe)2), 2, reacts with PPh2Me to yield the same Co-and P-chiral phosphinate products as obtained for the reaction of 1a with PPh(OMe)2, albeit with different optical yields. The product stereochemistry is not accounted for by the established mechanism for transition metal Arbuzov-like dealkylations, which requires formation of a common, ionic intermediate [CpCo(C3F7)(PPh2Me)(PPh(OMe)2)]+, 3, via iodide substitution and subsequent nucleophilic attack at carbon. A parallel intramolecular dealkylation pathway is proposed to account for the results. Key words: stereochemistry, mechanism, Arbuzov, Co(III) complex, chiral metal. X-ray
Parallel vs. perpendicular alkyne coordination in binuclear complexes. The first examples of reactivity differences in isomers differing in their alkyne coordination modes
Authors: George Darren S.A. , McDonald Robert , Cowie Martin
Published: May 2006

The reaction of [Ir2(CO)3(dppm)2] (dppm = Ph2PCH2PPh2) with dimethyl acetylenedicarboxylate (DMAD) first yields [Ir2(CO)2(μ-η1:η1-DMAD)(dppm)2] (2) in which the alkyne is bound parallel to the metal–metal axis and the diphosphines are bound in a trans arrangement at both metals. This metastable isomer slowly rearranges to the stable form, [Ir2(CO)2(μ-η2:η2-DMAD)(dppm)2] (3), in which the alkyne is now bound perpendicular to the metals and the diphosphines are bent back in a cis arrangement at both metals. The analogous species can be prepared by substituting hexafluoro-2-butyne (HFB) for DMAD; however, for the HFB adduct the isomer having the parallel geometry is seen only as a transient species; only [Ir2(CO)2(μ-η2:η2-HFB)(dppm)2] (5) was isolated. Compound 2 reacts readily with PMe3 to yield [Ir2(CO)(PMe3)(μ,-CO)(μ-η1:η1-DMAD)(dppm)2], and with CH3OSO2CF3 to yield [Ir2(CH3)(CO)2(μ-η1:η1-DMAD)(dppm)2][SO3CF3], whereas 3 reacts with neither reagent. Both 2 and 3 react with HBF4•OEt2 to yield the respective alkyne-bridged hydrides, [Ir2H(CO)2(μ-η1:η1-DMAD)(dppm)2][BF4] and [Ir2H(CO)2(μ-η2:η2-DMAD)(dppm)2][BF4], in which the gross structural features and the alkyne coordination mode of the precursor are retained in each case. The latter species rearranges readily at ambient temperature, via migratory insertion, to give the vinyl-bridged product, [Ir2(CO)2(μ-η1:η2-RC=C(H)R)(dppm)2][BF4] (R = CO2Me); however, the former is inert under these conditions, yielding the above vinyl species together with other decomposition products only upon reflux in benzene for several hours. Protonation of the perpendicular hexafluoro-2-butyne adduct also yields the corresponding vinyl product, together with decomposition products. The structure of 3, as the methylene chloride disolvate, was established by X-ray analysis. Crystal data are as follows. 3•2CH2Cl2: C60H54Cl4O6P4Ir2, monoclinic, P2/c, a = 26.088(5) Å, b = 9.896(4) Å, c = 23.954(3) Å, β = 109.27(1)°, Z = 4, R(F) = 0.038, Rw(F2) = 0.0997 (all data). Key words: diiridium alkyne complexes, parallel and perpendicular alkyne coordination.
Steric effects of bulky phosphines on 95Mo NMR shieldings
Authors: Song Shuquan , Alyea Elmer C.
Published: May 2006

Three sets of substituted molybdenum carbonyl complexes of the type Mo(CO)6−n(PY3)n (n = 1–3) with a wide range of phosphorus ligands (Y = Ar, R, OR, NR2, Cl, H) were synthesized and their respective 95Mo NMR spectral data were collected. The steric effect of PY3 plays an unexpectedly important role in the paramagnetic shielding term determining δ(95Mo), and is even observed in the least crowded M(CO)5(PY3) complexes. It is deduced that the steric requirement reduces the commonly accepted π-ability of phosphites by weakening the M—P bonds, making δ(95Mo) positions move toward higher frequency in going from M(CO)5(PY3) to fac-M(CO)3(PY3)3. A detailed correlation analysis in the case of phosphite ligands has shown that the free cone space to accommodate a PY3 ligand may be as low as 95° in Mo(CO)6−n(PY3)n (n = 1–3) derivatives. The fair linearity of these correlations suggests indirectly that the σ-component in phosphite bonding is relatively less important. These linear correlations of δ(95Mo) against the Tolman cone angle θ provide an empirical estimation of the bulkiness of any phosphite ligand. Key words: metal–phosphorus bonds, 95Mo NMR, steric effects.
The reactions of [Pd2Cl2(μ-PP)2] (PP = dppm, dmpm) with Et2NC≡CNEt2in methylene chloride solution: X-ray crystal structures of [Pd2Cl2(μ-CH2)(μ-dppm)2] and hexakis(diethylamino)benzene, C6(NEt2)6
Authors: Klopfenstein Sean R. , Kluwe Constanze , Kirschbaum Kristin , Davies Julian A.
Published: May 2006

The binuciear palladium(I) complex, [Pd2Cl2(μ-dppm)2] (dppm = bis(diphenylphosphino)methane), has been shown to react with bis(diethylamino)acetylene, Et2NC≡CNEt2, in methylene chloride solution to yield two isolable products, the known methylene-bridged complex, [Pd2Cl2(μ-CH2)(μ-dppm)2], and hexakis(diethylamino)benzene, C6(NEt2)6, both of which have been characterized crystallographically. The source of the bridging methylene group in [Pd2Cl2(μ-CH2)(μ-dppm)2] has been shown to be the methylene chloride solvent. A mechanism that accounts for the formation of the two isolable products is proposed. The complex, [Pd2Cl2(μdmpm)2] (dmpm = bis(dimethylphosphino)methane), was similarly found to react with Et2NC≡NEt2in methylene chloride solution to yield [Pd2Cl2(μ-CH2)(μ-dmpm)2], which was identified spectroscopically. Key words: acetylene, palladium, cyclooligomerization, aminoacetylene, hexakis(diethylamino)benzene.
Quantitative elemental and structural analysis of dissolved organic carbon fractions from lakes near Sudbury, Ontario
Authors: Boerschke Roy Carl , Gallie Elizabeth Ann , Belzile Nelson , Gedye Richard Neville , Morris James Robert
Published: May 2006

Dissolved organic carbon (DOC) was quantitatively isolated as five separate fractions from two Sudbury area lakes (Ontario, Canada) using the tandem XAD-8/XAD-4 resin technique. Fulvic acids made up ≈ 48% of the total, humic acids ≈ 8%, hydrophobic neutrals ≈ 8%, XAD-4 acids ≈ 11%, and XAD-4 acetonitrile extracts ≈ 13%. Hydrophobic:hydrophilic ratios were about 65:35. Solid-state CPMAS 13C NMR indicated a primarily aliphatic nature in all fractions. Percent aromaticity was in the order humic acids > fulvic acids > XAD-4 acetonitrile extracts ≈ XAD-4 acids ≈ hydrophobic neutrals. Titration analysis showed that the 13C NMR peaks of fulvic acids, humic acids, and XAD-4 acids from 160–190 ppm were primarily carboxyl in nature. The XAD-4 acids were the most acidic, suggesting that they may be important geochemical agents. 13C NMR indicated that polysaccharides formed < 20% of any fraction. The two neutral fractions (hydrophobic neutrals and XAD-4 acetonitrile extracts) had relatively high N contents, possibly due to the acetonitrile used to extract them. However, the 13C NMR spectra did not show significant quantities of acetonitrile. The elemental and structural composition covaries in the three acid fractions, such that if one acid is enriched or depleted, so are the others. This suggests that the humic and non-humic acids form a continuum in which all fractions are affected by the same formative processes. Compared to published data for other freshwater samples, the three acid fractions from the Sudbury area lakes have low or very low aromaticity. This may indicate that the acid and metal loadings in the Sudbury area have affected the structure of the organic acids, despite the circumneutral character of the study lakes. These are the first quantitative 13C NMR results published for the hydrophobic neutrals and XAD-4 acetonitrile extracts, so comparisons are not possible. Key words: aquatic DOC, organic acids, 13C NMR, humic substances, non-humic substances.
The mechanism of oxidation of 3-mercaptopropionic acid
Authors: Forlano Paula , Olabe José A. , Magallanes Jorge F. , Blesa Miguel A.
Published: May 2006

The mechanism of the oxidation of 3-mercaptopropionic acid (3-MPA) by hydrogen peroxide was studied in the acidic pH range. The nucleophilic attack by sulphur on the peroxide bond controls the rate. Extrapolation of the pH dependency suggests that the rate of attack by the deprotonated dianion is highest. Traces of Fe(III), at levels below 10−7 mol dm−3, do not catalyze efficiently the process through one-electron mechanisms; at higher concentrations, or on the surface of iron(III) oxides, this type of catalysis becomes important. The electrochemical oxidation of 3-MPA was also studied, using differential pulse polarography and cyclic voltammetry techniques. The mechanism is of the EC2E type, the second electron transfer step corresponding to the oxidation of the disulphide RS-SR. The rate constant for the dimerization of the RS• radicals was 1.8 × 103 mol−1 dm3 s−1; the slowness of this step agrees with the mechanisms observed in the course of one-electron oxidations by metal ions. Keywords: electrochemistry, kinetics, 3-mercaptopropionic acid, autooxidation.
The X-ray structure of a sodium peroxide hydrate, Na2O2•8H2O, and its reactions with carbon dioxide: relevance to the brightening of mechanical pulps
Authors: Hill Geoffrey S. , Holah David G. , Kinrade Stephen D. , Sloan Todd A. , Magnuson Vincent R. , Polyakov Valery
Published: May 2006

The main component of the solid originally believed to be a peroxosilicate with pulp-brightening properties has been shown to be Na2O2•8H2O. The solid crystallizes in the monoclinic space group C2/c, with an empirical formula H8O5Na, and with a = 14.335(3), b = 6.461(1), c = 11.432(2) Å, β = 118.28(3)°, and Z = 8. The centrosymmetric structure consists of a peroxide anion with an O—O distance of 1.499(2) Å. Each of these oxygen atoms is at the apex of an approximate square-based pyramid, the base of which consists of four oxygen atoms of water molecules. The bases of the two pyramids are staggered when viewed down the peroxide bond. Each sodium is at the centre of an approximate octahedron of water molecules, four of which bridge other sodium atoms and two bridge to the peroxide anions. One hydrogen atom of each of these two water molecules is terminal and the other two are hydrogen bonded to peroxide oxygen atoms. The compound reacts very rapidly with CO2 in moist air to form Na2CO3, but in drier conditions, formation of the carbonate can take many days and proceeds via a percarbonate, believed to be Na2CO4. This has been identified by infrared spectroscopy and X-ray powder diffraction and can persist for long periods in dry air. Key words: sodium peroxide hydrate, sodium percarbonate, pulp brightening, X-ray diffraction, infrared.
Substituent effects on basicity in Group 15 compounds: an analysis based on proton affinities, charge distributions, and dipole polarizabilities
Authors: Howard S.T. , Foreman J.P. , Edwards P.G.
Published: May 2006

Ab initio calculations on a series of trisubstituted amines, phosphines, and arsines are presented at the MP2/6-311G(d,p) level. Specifically, the species studied are XH3, XF3, and X(Me)3, where X = N, P, or As. The influence of the substituents on the proton affinity is analyzed in terms of the charge distribution, its topology, some one-electron properties (dipole moments, electric field gradients), and dipole polarizabilities. An atoms-in-molecules. decomposition of the charge distribution, energetics, and polarizabilities also proves informative. There seems to be no straightforward way of rationalizing the basicities of these compounds on the basis of electrostatic properties (i.e., properties of the charge distribution in the unprotonated bases). However, substituent effects on basicities can be correlated with response properties, such as the molecular (and atoms-in-molecules) polarizability tensors, and the amount of charge that a substituent group or atom donates on protonation. Key words: quantum chemistry, proton affinity, electron density, lone pairs, polarizability, basicity, dipole moment, electric field gradient.
Effect of β-cyclodextrin on the reaction of α-amino acid anions with p-nitrophenyl acetate and p-nitrophenyl hexanoate
Authors: Tee Oswald S. , Gadosy Timothy A. , Giorgi Javier B.
Published: May 2006

The effects of β-cyclodextrin (β-CD) on the kinetics of the reaction of α-amino acid anions with p-nitrophenyl acetate (pNPA) and p-nitrophenyl hexanoate (pNPH) have been investigated. Pseudo-first-order rate constants obtained with various concentrations of nucleophile and β-CD, in aqueous solution at pH 9.88, were analyzed to yield rate constants for reaction of the nucleophiles with free ester (kN) and with ester bound to β-CD (kcN). For pNPA reacting with amino acids that bind weakly to β-CD, if at all, the ratio kcN/kN is very close to one, but for amino acids that bind appreciably to β-CD this ratio is greater than one (up to 3.5). Generally similar behaviour is observed for reactions with pNPH, but the rate ratios are smaller and all less than one. These findings are comparable to those obtained in this laboratory for the CD-mediated reactions of p-nitrophenyl alkanoate esters with other nucleophiles, including simple alkylamines that bind quite strongly to CDs, but they differ from those reported in an earlier study of the reaction of pNPA with amino acid anions (Can. J. Chem. 69, 1124 (1991)) where the data analysis suggested more substantial catalysis by cyclodextrins. Key words: amino acids, cyclodextrin, ester cleavage, kinetics, catalysis.
Solubility of trans-stilbene in organic nonelectrolyte solvents. Comparison of observed versus predicted values based upon mobile order theory
Authors: Fletcher Kristin A. , McHale Mary E.R. , Coym Karen S. , Acree Jr. William E.
Published: May 2006

Experimental solubilities are reported at 25.0 °C for trans-stilbene dissolved in 28 different organic nonelectrolyte solvents containing methyl, ether, hydroxy, and tert-butyl functional groups. Results of these measurements are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 20 solvents for which predictions could be made, computations show that Mobile Order theory does provide fairly reasonable (although by no means perfect) estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is ca. 24%. In comparison, the average absolute deviation increases significantly to 935% when ideal solution behavior is assumed. KeyWords: trans-stilbene solubilities, organic nonelectrolyte solvents, solubility predictions.
Energétique des liaisons inter- et intramoléculaires dans les trois isomères du benzènediamine
Authors: Sabbah Raphaël , Perez Laurence
Published: May 2006

The present work is concerned with a thermodynamic study of the three benzenediamine (BDA) isomers (general formula: C6H8N2). It was achieved using four techniques: combustion calorimetry of small amounts of substance (a few milligrams), sublimation calorimetry, differential thermal analysis, and heat capacity measurements. From this study it was possible: to determine the enthalpies of combustion; sublimation, and fusion of these compounds as well as their triple point temperatures; to discuss the relative stability of the three molecules; to determine the experimental resonance energies and to compare them with the theoretical values; to determine the atomization enthalpies and to compare them with the values calculated from the energetical contributions previously obtained in our laboratory; to determine the intermolecular enthalpy bonds; to consider the existence of an intramolecular hydrogen bond in the ortho isomer. Keywords: benzenediamine isomers; enthalpy of combustion, of sublimation, of fusion, of inter- and intramolecular bonds.
Reactions of vanadate with N,N- dimethylhydroxylamine: aqueous equilibria and the crystal structure of the uncharged oxygenbridged dimer of bis(N,N-dimethylhydroxamido)hydroxooxovanadate
Authors: Paul Pradip C. , Angus-Dunne Sarah J. , Batchelor Raymond J. , Einstein Frederick W.B. , Tracey Alan S.
Published: May 2006

51V nuclear magnetic resonance spectroscopy has been utilized in the investigation of the reactions of vanadate with N,N-dimethylhydroxylamine in aqueous medium. The major components of the reaction products were mono- and bisliganded mononuclear vanadate compounds with 51V chemical shifts near −630 and −740 ppm, respectively. Variation of the concentration of the reactants enabled the determination of stoichiometry and formation constants of the products. The two major signals near −740 ppm were assigned to two stereoisomers of a bisligand product. The proton stoichiometrics and pKa values of the major products were determined from pH variation studies. A crystalline product of the type [V(O)(ONMe2)2]2O was isolated from the reaction of vanadate with dimethylhydroxylamine and its structure determined from X-ray diffraction studies. The compound possesses a dimeric oxo-bridge structure with a six-coordinate vanadium core. The arrangement about each vanadium may be described as approximately tetrahedral considering the center of the N—O bond in each dimethylhydroxamide ligand as one vertex. Hydrolysis of the crystalline solid in D2O provided two isomers that corresponded to the two bisligand products. A variable temperature 1H NMR study in D2O and 50% D2O/(CD3)2CO mixture revealed the existence of reasonably fast chemical exchange between the two predominant isomers. The nature of coordination of these and related compounds is discussed. Crystal structure of [V(O)(ONMe2)2]2O: orthorhombic, space group P22121;Z = 2;a = 7.0955(9) Å; b = 10.2313(12) Å; c = 11.5942(11) Å; V = 841.69 Å3; T = 213 K; RF = 0.021 for 1141 data (I0 ≥ 2.5σ(I0) ) and 137 variables. Keywords: bis(N,N-dimethylhydroxamido)hydroxooxovanadate, vanadate, dimethylhydroxylamine, vanadium NMR, aqueous equilibria, peroxovanadate.
Modeling of transfer properties using revised HKF theory: thermodynamics of transfer of an amino acid and small peptides from water to urea–water solutions at 298.15 K
Authors: Hakin Andrew W. , Groft Lori L. , Marty Jocelyn L. , Rushfeldt Matthew L.
Published: May 2006

Relative densities, [Formula: see text] and heat capacity ratios, [Formula: see text] have been measured for aqueous solutions of glycine, glycylglycine, and glycylglycylglycine in aqueous urea solutions containing 1–13 mol kg−1 urea. These data have been used to calculate apparent molar volumes, [Formula: see text] and apparent molar heat capacities, [Formula: see text] which in turn have been used to obtain standard state volumes, [Formula: see text] and standard state heat capacities, [Formula: see text].Volumes and heat capacities of transfer from water to urea have been calculated from our reported standard state data. Heat capacities of transfer of the investigated systems have been modeled using a procedure developed from the semiempirical calculation procedures proposed by Helgeson, Kirkham, and Flowers. Keywords: amino acids, peptides, calorimetry, transfer thermodynamics, HKF theory.
Observation of a single-pot aromatic reductive denitration
Authors: Giumanini Angelo G. , Verardo Giancarlo
Published: May 2006

4,N,N-Trimethyl-3-nitrobenzenamine gave reductive denitration products (ca. 28%) upon treatment with n-butyl nitrite in the presence of catalytic amounts of ammonium chloride and water in an unprecedented one-reagent single-pot process. The three isomeric N,N-dimethylnitrobenzenamines showed the same behaviour to a much lesser extent; the ortho isomer was partially (7%) transformed into 1-methylbenzotriazole. Keywords: aromatic protolytic denitration, nitroaromatics, n-butyl nitrite, E- and Z-nitrosamine.
Réactivité dipolaire-1,3 du 4,4,4-trichiloro-3-éthoxycarbonylamino-2-diazobutyrate d'éthyle issu de l'action du diazoacétate d'éthyle sur la N-éthoxycarbonyl-N-(2,2,2-trichloroéthylidène)amine
Authors: Belaissaoui Abdelhak , Jacquot Sandrine , Morpain Claude , Schmitt Gérard , Vebrel Joël , Laude Bernard
Published: May 2006

The reaction of ethyl diazoacetate with the N-ethoxycarbonyl-N-(2,2,2-trichloroethylidene)amine yields, by a nucleophilic addition, a new diazo compound that gives 1,3-dipolar cycloaddition reactions with acetylenic esters and maleimides. With acetylenic esters, the cycloadduct leads to substituted pyrazoles by [1,5] sigmatropic rearrangements. With maleimides, we observe a diastereospecific cycloaddition reaction. The intermediary cycloadduct evolves by nitrogen elimination to give a maleimidocyclopropane. The diastereospecificity was explained by an endo-anti approach of the reactants. Keywords: N-ethoxycarbonyl-N-(2,2,2-trichloroethylidene)amine, ethyl diazoacetate, nucleophilic addition, 1,3-dipolar cycloaddition, sigmatropic rearrangement, diastereoselectivity.
Isolation, structure, and synthesis of chenopodanol and the absolute configuration of chenopodene and chenopodanol
Authors: Tori Motoo , Hamaguchi Tomonobu , Aoki Mamiko , Sono Masakazu , Asakawa Yoshinori
Published: May 2006

(−)-Chenopodanol (2) has been isolated from the liverwort Marchantiachenopoda and its structure determined by spectroscopic techniques as well as by total synthesis. Chenopodene (1) has also been synthesized in an optically active form, resulting in revision of the originally assigned absolute configuration. Keywords: chenopodanol, chenopodene, liverwort, Marchantiachenopoda, sesquiterpene.
Total synthesis of mycophenolic acid
Authors: de la Cruz Ricardo A. , Talamás Francisco X. , Vázquez Alfredo , Muchowski Joseph M.
Published: May 2006

A total synthesis of mycophenolic acid is reported. Diels–Alder reaction of [5-methoxy-3-(1-methoxypropenyl)-4,5-dihydrofuran-2-yloxy]-trimethylsilane with 3-benzenesulfinyl-5H-furan-2-one afforded the hexasubstituted nucleus. The side chain was constructed from the unveiled aldehyde. Keywords: mycophenolic acid, Diels–Alder reaction, pentasubstituted diene.
Regio- and stereoselective ring openings of unsymmetrical oxatricyclo adducts
Authors: Woo Simon , Parvez Masood , Keay Brian A.
Published: May 2006

SN2′ ring-opening reactions of a number of substituted 11-oxatricyclo[6.2.1.01,6]undec-9-en-5-ones prepared via the intramolecular Diels–Alder reaction employing a furan diene (IMDAF) are reported. Primary, secondary, and tertiary organolithium reagents were capable of effecting the ring-opening reaction, while methyllithium required activation before any ring opening was observed. Hydride reagents, organocuprates, and Grignard reagents were generally ineffective. The ring-opening reaction was highly regio- and stereoselective for attack at C9syn to the bridging oxygen atom provided that C8 was not substituted. A highly stereoselective nucleophilic addition to the carbonyl group anti to the bridging oxygen was also observed. The high selectivity appears to be due to a combination of steric and electronic effects. Keywords: SN2′ reactions, oxatricyclo adducts, Diels–Alder reaction, ring opening.
5-Hydroxypentane-2,3-dione and 3-amino-1-hydroxypropan-2-one, putative precursors of vitamin B6
Authors: Wolf Eckardt , Kennedy Isaac A. , Himmeldirk Klaus , Spenser Ian D.
Published: May 2006

New syntheses are described of 5-hydroxypentane-2,3-dione (7) (i.e., laurencione [Formula: see text]) and of 3-amino-1-hydroxypropan-2-one (3-amino-1-hydroxyacetone) (5) hydrochloride, putative precursors of the C5 unit, C-2′,2,3,4,4′, and of the C3N unit, N-1,C-6,5,5′, respectively, of pyridoxine (6). Keywords: 3-amino-1-hydroxyacetone, 3-amino-1-hydroxypropanone, 5-hydroxypentane-2,3-dione, laurencione, vitamin B6.
Formation of quaternary centres via iron allyl cations. Rapid entry into spirocyclic ring systems
Authors: Charlton M. Anne , Green James R.
Published: May 2006

Ester-substituted allyltetracarbonyliron cations react with cycloalkylidene-type silyl enol ethers, silyl ketene acetals, and β-keto-esters to give 1,6-dicarbonyl compounds containing a newly formed quaternary centre. Selected condensation products are converted by enolate chemistry into spirocyclic [4.4], [4.5], and [4.6] systems. Acyloin and other reductive cyclization reactions are employed to convert the condensation products into spirocyclic [4.5], [5.5], and [5.6] systems. Keywords: allyliron complexes, umpolung synthesis, 1,6-dicarbonyls, spirocycle synthesis.
A novel approach to carbohydrate clusters: the regioselective synthesis of non-glycosidically linked oligosaccharides
Authors: Namazi Hassan , Grindley T. Bruce
Published: May 2006

Dialkylstannylene acetals derived from a number of different carbohydrates having both cis- and trans-1,2-diols free were reacted with diacyl chlorides and disulfonyl chlorides in the presence of tertiary amines at room temperature to give symmetrical non-glycosidically linked disaccharides with excellent regioselectivity and in excellent yield. The regioselectivity obtained was the same as that previously found in acylation reactions of the same substrates. In one case, a symmetric non-glycosidically linked diasaccharide was also obtained in excellent yield. For methyl 4,6-O-benzylidene-α-D-glucopyranoside, a 16-membered ring macrocyclic tetralactone was obtained in 50% yield by altering the reaction stoichiometry and performing the reaction at 80 °C. Keywords: carbohydrates, clusters, non-glycosidically linked oligosaccharides, disaccharides, trisaccharides.
The mechanism of the hydrolysis of acylimidazoles in aqueous mineral acids. The excess acidity method for reactions that are not acid catalyzed
Authors: Cox Robin A.
Published: May 2006

The mechanism of the hydrolysis of acetylimidazole in aqueous perchloric, sulfuric, and hydrochloric acid mixtures has been determined. Benzoylimidazole was also studied in the latter two acids. The method of analyzing the available data, pseudo-first-order reaction rate constants as a function of acid concentration and, in one case, temperature, is the excess acidity method, here applied to the same reaction in the three different acid media, allowing their comparison. The reaction is not acid catalyzed; the rates decrease with increasing acidity. The substrate reacts in the form that is monoprotonated on the imidazole ring; it is 100% protonated at acidities much lower than those used here. Acetylimidazole is shown to become diprotonated at high acidity [Formula: see text], protonating on the carbonyl oxygen, but the diprotonated form is not reactive. The hydrolysis involves the reversible addition of one water molecule to the substrate to give a tetrahedral intermediate; at low acidities the decomposition of this hydrate is the rate-determining step, but as the acidity increases and the water activity decreases its formation becomes rate limiting. Hydroxide catalysis was also observed in dilute perchloric acid, but this is swamped by nucleophilic catalysis by the acid anion in HCl and H2SO4. Keywords: acylimidazoles, excess acidity, hydrolysis, protonation, tetrahedral intermediate.
Calorimetric investigations of Al3+(aq), Al(OH)4−(aq), and aluminium–citrate complexes at 298.15 K
Authors: Wu Ching-hsien , Dobrogowska Celina , Zhang Xin , Hepler Loren G.
Published: May 2006

We have combined results of earlier measurements leading to equilibrium constants for formation and reaction of aluminum–citrate complexes in aqueous solution at 298.15 K with results of our calorimetric measurements at this same temperature to obtain ΔH values for reactions of Al3+(aq) with citrate ions. Results of some of these calorimetric measurements also lead to a value of ΔH for the reaction Al3+(aq) + 4 OH`(aq) = Al(OH)4−(aq). Keywords: aluminum hydroxide, Al(OH)4−(aq), thermodynamics; aluminium–citrate complexes, thermodynamics; citrate–aluminum complexes, thermodynamics; aluminum (3+, aq), thermodynamics.
Electrochemical reduction of the unsaturated cyclic trinuclear Pd3(dppm)3CO2+ cluster (dppm = ((C6H5)2P)2CH2)
Authors: Gauthron Isabelle , Mugnier Yves , Hierso Karine , Harvey Pierre D.
Published: May 2006

Pd3(dppm)3CO2+ exhibits a two-electron reduction process at ~ −0.5 V vs. SCE in 0.2 M Bu4NPF6 solutions of organic solvents such as dry acetonitrile, N,N-dimethylformamide (DMF), tetrahydrofuran (THF), and dichloromethane to reversibly produce the zero valent Pd3(dppm)3CO, which exhibits a ν(CO) band in the 1761–1766 cm−1 range in the IR spectra. The mechanistic aspects of this multistep two-electron process are discussed experimentally on the basis of r.d.e. (rotating disk electrode) voltammetry, cyclic voltammetry, and electrolysis results. Geometry optimizations using DFT (Density Functional Theory) predict that the Pd—Pd and C=O bond lengths are 3.008 and 1.182 Å, respectively, which compare favorably with the experimental data for other zero valent polynuclear complexes. Keywords: palladium, cluster, reduction, electrochemistry, density functional theory.
Ring A building blocks for taxoids and taxamycins
Authors: Tjepkema Michael W. , Wilson Peter D. , Audrain Hélène , Fallis Alex G.
Published: May 2006

The syntheses of a series of oxygenated cyclohexene ring A synthohs 20, 22–27, 34, 36, and 37 that possess suitable functionality for further elaboration for taxoid synthesis are described. These compounds have been prepared from β-ionone by a series of oxidative and addition reactions or alternatively by Lewis acid catalyzed Diels–Alder cycloadditions with the oxygen-containing trimethyl substituted dienes 31 and 33. Keywords: taxoid, paclitaxel, dienes, Diels–Alder, β-ionone.
2-Trichloromethylimidazole. Condensation reactions with anions stabilized by carbonyl groups
Authors: González Jaime , Pérez-Medrano Arturo , Muchowski Joseph M.
Published: May 2006

2-Trichloromethylimidazole 2, a stable but moisture-sensitive solid, is readily prepared by cyclization of the amidine 1 in trifluoroacetic acid (99+%). Compound 2 reacted with the enolates derived from 1,1-di- and monocarbonyl compounds to give the β-chlorovinyl carbonyl compounds 5a–c and 6a, b, respectively. Keywords: 2-trichloromethylimidazole, condensation reactions, mono- and dicarbonyl compounds.
Zirconium alkyl and borohydride complexes stabilized by a sterically demanding anionic organic amide. The crystal structures of ZrMeL3 (2) and Zr(BH4)L3 (3) (L = (3,5-Me2Ph)N(Ad); Ad = adamantyl)
Authors: Kasani Aparna , Gambarotta Sandro , Bensimon Corinne
Published: May 2006

The lithium amide [3,5-Me2PhN(Ad)]Li•Et2O (L) reacts with ZrCl4(THF)2 to give ZrClL3. Reactions of ZrClL3 with MeLi and NaBH4 produce the corresponding ZrMeL3 (2) and Zr(BH4)L3 (3), respectively. The molecular structures of 2 and 3 were determined by X-ray crystallography. Crystal data are as follows. 2: C55H75N3Zr, FW 869.45, orthorhombic, Pcab; a = 19.2436(3) Å,b = 45.9342(4) Å, c = 21.2935(3) Å, V = 18822.2(4) Å3Z = 8; 3: C54H76BN3Zr, FW 869.25, orthorhombic; Pbc21, a = 11.5399(3) Å,b = 19.4091(4) Å, c = 20.4471(5) Å,V = 4579.72(19) Å3Z = 4. Keywords: zirconium, amide, alkyl, borohydride, structure.
Temperature dependence of activity coefficients and Gibbs energies of transfer of LiBr in acetonitrile, dimethyl sulfoxide, and N,N-dimethylacetamide from EMF measurements
Authors: Barthel J. , Neueder R. , Schröder A.
Published: May 2006

Electromotive force (EMF) measurements based on the redox reaction[Formula: see text]are reported for solutions of LiBr at concentrations 0.005 < cLiBr/(mol dm−3) < 0.1 in acetonitrile (AN), dimethyl sulfoxide (DMSO), and N.N-dimethylacetamide (DMA) in the temperature range 278.15 < T/K < 308.15. Gibbs energies of transfer and activity coefficients are estimated. The association constants of LiBr in AN, DMSO, and DMA from EMF measurements and the enthalpy of transfer AN → DMSO are compared to those from other methods of determination. Keywords: temperature-dependent EMF measurements, aprotic solvents, LiBr, TlBr(s) | TlxHg(l) electrode, activity coefficients, transfer quantities.