bluuebunny/crossref_metadata_2025 huggingface dataset:
Rate and equilibrium constants for formation and hydrolysis of 9-formylfluorene oxime: diffusion-controlled trapping of a protonated aldehyde by hydroxylamine
Authors: O'Ferrall RA More , O'Brien D M , Murphy D G
Published: April 2011

Equilibrium constants Kadd = 440 and Kox = 3.0 × 108 for formation of a carbinolamine adduct and oxime, respectively from 9-formylfluorene and hydroxylamine, and pKa = 1.62 for protonation of the oxime, have been evaluated at 25°C in aqueous solution, based on measurements in hydroxylamine buffers, acetic acid buffers, and dilute HCl. Rate constants for hydrolysis of the oxime have been measured in the acidity range pH 412 M HClO4. At the highest acidities, a reaction pathway via protonated carbinolamine has been identified: evidence is presented that the reverse of this reaction involves rate-determining attack of hydroxylamine upon protonated 9-formylfluorene. By assuming that the attack of hydroxylamine is diffusion-controlled, with rate constant 3 × 109 M 1 s1, a pKa for O-protonation of the aldehyde (4.5) is derived. Taking account of the equilibrium constant for enolization of 9-formylfluorene (KE = 16.6), a pKa for for C-protonation of the enol tautomer ((5.7) may also be obtained. Comparison of this pKa with that of the enol of acetophenone shows that the enol of 9-formylfluorene is less basic by a factor of 1010. By combining pKas for protonation of the aldehyde and oxime with measured or estimated equilibrium constants for addition of water, hydroxide ion, and hydroxylamine to 9-formylfluorene, it is also possible to obtain values of pKR = 5.3, 4.1, and 12.25 for the protonated 9-formylfluorene, protonated oxime, and 9-formylfluorene, respectively. The usefulness of pKR in providing a general measure of equilibrium constants for electrophile-nucleophile combination reactions is discussed.Key words: oxime, formyfluorene, hydrolysis, protonation, diffusion-control.
Molecular and electronic structure of AnIVFeII(CN)6·xH2O (An = Th, U, Np) compounds: an X-ray absorption spectroscopy investigation
Authors: Bonhoure Isabelle , Auwer Christophe Den , Moulin Christophe Cartier dit , Moisy Philippe , Berthet Jean-Claude , Madic Charles
Published: April 2011

AnIVFeII(CN)6·xH2O (An = Th, U, Np) molecular compounds have been prepared by precipitation from acidic media. These microcrystalline compounds have been characterized by infrared spectroscopy, X-ray diffraction, and X-ray absorption spectroscopy. They have been found to be isostructural with the LnIIIKFeII(CN)6·4H2O compounds. The molecular structures of these compounds are presented and their chemical formulas are given: in all compounds, the Fe(CN)6octahedra is conserved and the An ion is linked to the N atoms of the CN ligands. The formal oxidation states are also discussed.Key words: hexacyanoferrate, actinide, EXAFS, XANES, X-ray absorption spectroscopy.
Nitrones and oximes of bifunctional carbonyl compounds and their reaction products with diarylborinic acids. Crystal and molecular structure of examples of five-, six-, and seven-membered boron chelates
Authors: Kliegel Wolfgang , Lubkowitz Gottfried , Pokriefke Jens O , Rettig Steven J , Trotter James
Published: April 2011

Synthesis has been carried out of diarylboron chelates of 2- and 3-hydroxynitrones, of 2- and 3-hydroxyoximes, and of 2-carboxynitrones and a 2-carboxyoxime. The structures have been determined from spectroscopic data and from X-ray analyses of 5d, 9a, 11b, and 19. Crystals (at 180 K) of 5d are monoclinic, a = 10.543(2), b = 19.085(4), c = 10.2667(3) Å, β = 90.4978(7)°, Z = 4, space group P21/c; those of 9a are orthorhombic, a = 10.9913(5), b = 14.9329(7), c = 10.2460(13) Å, Z = 4, space group P212121; those of 11b are monoclinic, a = 11.227(2), b = 9.967(2), c = 17.0537(4) Å, β = 105.4179(5)°, Z = 4, space group P21/n; those of 19 are monoclinic, a = 11.1847(15), b = 13.715(3), c = 11.5559(5) Å, β = 104.8730(10)°, Z = 4, space group P21/n. The structures were solved by direct methods and refined by full-matrix least-squares procedures to R(F, I [Formula: see text] 3σ(I)) = 0.049, 0.047, 0.042, and 0.047, respectively, for CCD data for 5d, 9a, 11b, and 19. The four molecules contain five-, seven-, six-, and five-membered rings, respectively, with O-B-N groups in the 5d, 11b, and 19, and O-B-O in 9a; the rings exhibit various deviations from planarity, particularly the seven-membered ring.Key words: diarylboron chelates, hydroxyoximes, hydroxynitrones, carboxyoximes, carboxynitrones, organoboron compounds, crystal structure.
Potentiometric study of cadmium(II) and lead(II) complexation by a cross-linked poly(acrylic acid). Comparison with the linear analogue
Authors: Morlay Catherine , Mouginot Yolande , Cromer Monique , Chatelut Michelle , Vittori Olivier
Published: April 2011

Cadmium(II) or lead(II) complex formation with an insoluble cross-linked poly(acrylic acid) was investigated in dilute aqueous solution (NaNO3 0.1 M, 25°C). Potentiometric titrations were carried out to determine the stability constants of the MA and MA2 complex species formed. The Bjerrum's method, modified by Gregor et al. (1955), for the study of polymeric acids was used. The results obtained showed that lead(II) was more readily bound to the polymer. PbA2 was the predominant species; the global stability constant log B102 was equal to 7.4. With cadmium(II), none of the complex species MA or MA2 was predominant (log B102 = 6.0). Finally, the comparison of these results with those of our previous studies showed that the insoluble cross-linked poly(acrylic acid) and its hydrosoluble linear analogues present similar complexing properties towards cadmium(II), lead(II), copper(II), and nickel(II).Key words: insoluble cross-linked poly(acrylic acid), cadmium(II), lead(II), complexation, potentiometry.
Preparation, X-ray structure, and dynamic solution behaviour of N,N',N''-tris(2,6-diisopropylphenyl)- guanidine, and its reaction with molybdenum carbonyl
Authors: Boeré Robyn E , Boeré René T , Masuda Jason , Wolmershäuser Gotthelf
Published: April 2011

The reaction of N,N'-bis(2,6-diisopropylphenyl)carbodiimide with lithium 2,6-diisopropylanilide, quenching with water and recrystallization from heptane produces the symmetric guanidine [DipNH]2C=NDip which crystallizes in the triclinic system, space group P[Formula: see text], a = 10.6513(11), b = 10.8997(11), c = 16.2961(17) Å, α = 80.524(12), β = 78.921(13), γ = 70.060(12)°, V = 1735.2(3) Å3, Z = 2. The molecule crystallizes with three perpendicular 2,6-diisopropylphenyl groups, which surround and shield the central CN3 unit, and provide (almost) three-fold symmetry around the central atom. Its dynamic solution behaviour has been studied by VT NMR between -90 and +180°C, and is consistent with three distinct barriers to N-CAr rotation. Preliminary estimates of the Gibbs free energy of activation for the lower two barriers are 56 ± 2 and 73 ± 2 kJ mol1. Reaction of the title compound with Mo(CO)6 in refluxing n-heptane produces [DipNH]2C=NDip·Mo(CO)3, a complex in which Mo(CO)3 is η6-coordinated to one of the diisopropylphenyl rings.Key words: crystal structure, diisopropylaniline, guanidine, bulky ligands.
Syntheses and electrochemical characterization of heteroleptic cyclopentadienyl-bis(dithiolene) complexes of niobium and tantalum
Authors: Jourdain I V , Guyon F
Published: April 2011

Diamagnetic niobium and tantalum complexes of general formula [M(η5-C5Me5)(dithiolene)2] have been prepared (M = Nb, dithiolene = dddt2 (5,6-dihydro-1,4dithiine-2,3-dithiolate) (1); M = Ta, dithiolene = dddt2 (2); M = Nb, dithiolene = dddt2 and dmit2 (1,3-dithiole-2-thione-4,5-dithiolate) (3)). All these complexes exhibit temperature-dependent 1H NMR spectra which result from a fluxional behavior of the dithiolene ligands. Their redox properties have been investigated by cyclic voltammetry and reversible oxidation processes involving the dithiolene ligands have been evidenced for the complexes 1 and 2.Key words: niobium, tantalum, dithiolene, voltammetry cyclic, variable-temperature 1H NMR.
Bis(trimethylsilyl)methanesulfonyl and tris(trimethylsilyl)methanesulfonyl chlorides and their reactions by way of sulfenes
Authors: King James F , Baines Kim M , Netherton Matthew R , Dave Vinod
Published: April 2011

Bis(trimethylsilyl)methanesulfonyl and tris(trimethylsilyl)methanesulfonyl chlorides (2c and 2d, respectively), have been prepared for the first time. Reactions of 2d with nucleophiles give products evidently derived from bis(trimethylsilyl)sulfene (1c). Reaction of 2c with piperidine gives the same piperidide as that from 2d, presumably via 1c formed by dehydrochlorination of 2c, whereas water and fluoride ion yield products consistent with their formation via trimethylsilylsulfene (1b) formed from 2c by attack at silicon with loss of the trimethylsilyl and chloro groups. No evidence for any enhanced stability in 1c was found.Key words: sulfonyl chlorides, sulfenes, silylsulfonyl chlorides, silylsulfenes, desilylation.
Synthesis and X-ray structure of 1,2,2,2-tetrakis(3-methoxyphenyl)ethanone
Authors: Klemm LeRoy H , Weakley Timothy JR
Published: April 2011

Photochemical reductive dimerization of 3,3'-dimethoxybenzophenone (1b) gave the symmetrical benzopinacol 1,1,2,2-tetrakis(3-methoxyphenyl)ethane-1,2-diol (2b), which was rearranged to the benzopinacolone 1,2,2,2-tetrakis(3-methoxyphenyl)ethanone (3b) by means of I2 in boiling glacial HOAc. The structure of 3b was indicated by 1H NMR and determined definitively by X-ray crystallography. The crystals are monoclinic, space group P21/c, a = 12.250(2), b = 9.6997(12), c = 20.866(2) Å, β = 95.319(11)°, Z = 4, R = 0.053 for 4523 independent reflections. The structure establishes that the migrating 3-methoxyphenyl group retains bonding through its number 1' carbon atom to the parent C2-unit during the rearrangement process.Key words: X-ray structure, pinacol-pinacolone rearrangement, chemical bonding.
Asymmetric synthesis based on chiral (arene)tricarbonylchromium acetal complexes. Addition reactions to the ortho-formyl complex
Authors: McKay M Kevin , Green James R
Published: April 2011

The addition reactions of organolithium and Grignard reagents to chiral, enantiomerically pure ortho-formyl (arene)tricarbonylchromium acetal complex (2) have been studied. The diastereoselectivity of the addition process is fair in the absence of an additional Lewis acid, and good in the presence of Ti(OiPr)4. The nature of the newly formed chiral centre, and studies on the possible nature of the nucleophilic species suggest that the Lewis acid acts through monodentate coordination to the aldehyde carbonyl, and thereby alters the carbonyl rotamer population more heavily in favour of the s-trans conformation. Nucleophilic attack then occurs on the face anti- to that bearing the Cr(CO)3 unit.Key words: (arene)tricarbonylchromium complexes, asymmetric synthesis, carbonyl additions, Lewis acids.
IR Spectroscopy of aqueous alkali halides. Factor analysis
Authors: Max Jean-Joseph , Blois Serge de , Veilleux Alain , Chapados Camille
Published: April 2011

The infrared spectra of ten salts in aqueous solutions were obtained in their solubility range using attenuated total reflection (ATR). The salts are: LiCl, NaCl, KCl, CsCl, MgCl2, NaBr, KBr, NaI, KI, and CsI. The salts, which are completely ionized in water, do not absorb in the IR. Only their interactions with water are observed and analyzed. Factor analysis (FA) applied to the spectra showed that two principal species are present in the solutions: pure water and salt-solvated water. The modifications of the water spectrum are dependent on the nature of the salts, their concentrations and are mainly of first-order. Second-order effects were observed but, being weak, were not investigated. The modifications of the IR-ATR spectrum from pure water to a salt solution are proportional to the modifications of the imaginary part of the refractive index spectrum (k(v)). This indicates that the anomalous dispersion effects do not interfere with the chemical analysis of the IR-ATR spectra. In every salt studied, the two main species present in the solutions remained stable throughout the salt solubility ranges. Comparison between the IR spectra of the different salts solutions indicates that both anions and cations are in strong interaction with water molecules and are solvated together in stable clusters.Key words: IR spectroscopy, ATR, liquid, aqueous solutions, factor analysis, principal spectra, LiCl, NaCl, KCl, CsCl, NaBr, KBr, NaI, KI, CsI, MgCl2.
Mechanistic study of ligand substitution processes in TpIr(III) complexes
Authors: Tellers David M , Bergman Robert G
Published: April 2011

The synthesis of the cationic hydridotris(pyrazolyl)borate iridium(III) complex [Tp(PMe3)IrMe(ClCH2Cl)][BArf] (2-CH2Cl2) is reported. Spectroscopic characterization of 2-CH2Cl2 in CH2Cl2 solution indicates that exchange of bound CH2Cl2 with free CH2Cl2 is slow on the NMR time scale. Under 50 atm (1 atm = 101.325 kPa) of N2, the CH2Cl2 in 2-CH2Cl2 is displaced by N2 to yield [Tp(PMe3)IrMe(N2)][BArf] (2-N2). The stronger nucleophile CH3CN reacts rapidly with 2-CH2Cl2 to produce [Tp(PMe3)IrMe(NCCH3)][BArf] (4). A kinetic study was performed on CH2Cl2 substitution in 2-CH2Cl2 by CD3CN. The data are most consistent with dissociative loss of CH2Cl2 to generate the unsaturated species ([Tp(PMe3)IrMe][BArf]) which then reacts with CD3CN to generate [Tp(PMe3)IrMe(NCCD3)][BArf]. Further evidence for a dissociative mechanism was obtained by comparison of ligand substitution rates for the Tp complexes with the analogous TpMe2 complexes (TpMe2 = hydridotris(3,5-dimethylpyrazolyl)borate). The relevance of these substitution experiments to CH activation by cationic iridium(III) complexes is discussed.Key words: iridium, hydridotris(pyrazolyl)borate, methylene chloride and dinitrogen complexes, dissociative substitution.
Hydrogen transfer from formic acid to alkynes catalyzed by a diruthenium complex
Authors: Gao Yuan , Jennings Michael C , Puddephatt Richard J
Published: April 2011

The diruthenium(0) complex [Ru2(µ-CO)(CO)4(µ-dppm)2] (1) (dppm = Ph2PCH2PPh2), is a catalyst for the transfer hydrogenation, using formic acid as hydrogen donor, of the alkynes PhCºCPh, PhCºCMe, EtCºCEt, and PrCºCPr but not of the terminal alkynes HCºCH, PhCºCH, BuCºCH, or the alkynes containing one or two electron-withdrawing substituents PhCºCCO2Me and MeO2CCtriple bondCCO2Me. In the successful reactions, the formic acid is first decomposed to carbon dioxide and hydrogen, which then hydrogenates the alkynes in a slower reaction. In the unsuccessful reactions, the decomposition of formic acid is strongly retarded by the alkyne. In the case with the alkyne PhCºCH, it is shown that the alkyne reacts with protonated 1 to give first [Ru2(µ-CPh=CH2)(CO)4(µ-dppm)2][HCO2], which then isomerizes to give the catalytically inactive, stable complex [Ru2(µ-CH=CHPh)(CO)4(µ-dppm)2][HCO2]. This complex has been structurally characterized and both of the µ-styrenyl complexes are shown to be fluxional in solution.Key words: ruthenium, hydrogenation, catalysis, binuclear..
Scope and limitations in the use of N-(PhF)serine-derived cyclic sulfamidates for amino acid synthesis
Authors: Wei Lan , Lubell William D
Published: April 2011

Ring-opening of N-(PhF)serine-derived cyclic sulfamidate 17 was achieved with different nucleophiles (β-keto esters, β-keto ketones, dimethyl malonate, nitroethane, sodium azide, imidazole, and potassium thiocyanate) to prepare a variety of amino acid analogs. Two different pathways for ring opening of 17 were elucidated: direct nucleophilic displacement, as well as β-elimination followed by Michael addition. Furthermore, β-keto ester and β-keto ketone products 18k,18m, and 18i were converted to prolines and pyrazole amino acids.Key words: glutamate, amino acid, cyclic sulfamidate, proline.
Hetero trinuclear oxo-bridged complexes of ruthenium porphyrin and iron phthalocyanine
Authors: Zobi Fabio , Stynes Dennis V
Published: April 2011

New diamagnetic hetero bi- and trinuclear oxo-bridged metal complexes of formula (L)(Pc)Fe-O-Ru(TPP')(O) and (L)(Pc)Fe-O-Ru(TPP')-O-Fe(Pc)(L) have been prepared from Ru(TPP')(O)2and Fe(Pc)(L)2(TPP' = tetrakis(4-methoxyphenyl)porphyrinate, Pc = phthalocyanate ion, L = monodentate ligand). The trinuclear complex binds a variety of ligands (4,4'-bipy, 4-MePy, P(OEt)3, pip, NH3, 1-MeIm, P(Me)2Ph) trans to the oxo-bridge.1H NMR spectra are characterized by large ring current shifts (rcs) due to the TPP' and Pc ions. The complexes show an unusually weak Pc Q band in their visible spectra at 700 nm and two CT bands in the near-IR region from 1000 to 1500 nm, which are sensitive to the trans ligand. The trinuclear complex can be reversibly oxidized to the +1 and +2 ions, formally Fe(IV)-O-Ru(IV)-O-Fe(III) and Fe(IV)-O-Ru(IV)-O-Fe(IV) at 0.4 and 0.76 V. The +1 ion is chemically obtained by reaction of the neutral species with (Cp)2Fe+for L = 4-MePy and this reaction is reversed upon addition of L' = P(Me)2Ph. Reductive cleavage by hydroquinone, phosphines and phosphites are the slowest of all RuTPP[O(FeN4)]2systems studied to date (t1/2= 8 h at 40°C).Key words: ruthenium, iron, porphyrin, phthalocyanine, oxo.
Structural, electronic and spectroscopic features of the dihydride Pd4(dppm)4(H)22+ cluster catalyst
Authors: Meilleur Daniel , Harvey Pierre D
Published: April 2011

1H NMR, vibrational, and UVvis spectroscopic measurements for Pd2(dppm)2Cl2 (dppm = Ph2PCH2PPh2), [Pd4(dppm)4(X)2](BF4)2 (X = Cl, H), and [Pd4(dmpm)4(H)2](Br)2 (dmpm = Me2PCH2PMe2) were performed to address the structure of the recently identified title cluster. Its dmpm analogue was prepared from the reaction between Pd2(dmpm)2Br2 and NaBH4 in methanol under inert atmosphere, and exhibits the expected nonet (rel. int. 1:8:28:56:70:56:28:8:1) at 5.21 ppm (in (CD3)2CO), contrasting with that of Pd4(dppm)4(H)22+ (δ + 5.15 ppm, (CD3)2CO). This significant difference is explained by the presence of the PdH residues in the deshielding region of the dppm-phenyl groups. The vibrational spectra in the low-frequency region are consistent with a centrosymmetric structure, and a scattering at 144 cm1 in the FT-Raman spectra is observed; a peak that is assigned to ν(Pd2) on the basis of a comparison with the well established M2-bonded Pd2(dppm)2Cl2 data ((Pd2) = 149 cm1). On the basis of the qualitative temperature behavior of the band maxima and width, the two lowest energy absorption bands in the UVvis spectra are assigned to d σ [Formula: see text] d σ * type transition. EHMO computations predict four well-isolated frontier MO levels, defined as d σ *(Pd2)/d σ *(PdH) (LUMO + 1), d σ *(Pd2) (LUMO), d σ *(Pd2)/d σ *(PdH) (HOMO), and d σ (Pd2) (HOMO 1), and simple selection rules (u « g) indicate that only two low-energy electronic transitions are orbitally allowed, consistent with the UVvis findings. Computer modelings show the presence of large cavities above and under the Pd4 plane, described by inner-cavity nonbonded H···H distances of ~58 Å.Key words: cluster, palladium, hydride, structure, spectroscopy.
Rh2Cl2(CO)4adsorbed and tethered on gold powder: IR spectroscopic characterization and olefin hydrogenation activity
Authors: Gao Hanrong , Angelici Robert J
Published: April 2011

Catalysts were prepared by adsorbing Rh2Cl2(CO)4directly on gold powder or on gold that contained the tethered ligands 2-(diphenylphosphino)ethane-1-thiol (DPET) or methyl 2-mercaptonicotinate (MMNT). Infrared (IR) studies (diffuse reflectance infrared Fourier transform (DRIFT)) of the catalyst RhAu prepared by adsorbing Rh2Cl2(CO)4directly on Au indicate that a RhI(CO)2species is present. IR studies of RhDPET-Au suggest that tethered cis-Rh(DPET)(CO)2Cl is the major species at relatively high Rh2Cl2(CO)4loadings, but trans-Rh(DPET)2(CO)Cl is observable at low Rh2Cl2(CO)4loadings. Spectral investigations of the catalyst RhMMNT-Au prepared by adsorbing Rh2Cl2(CO)4on MMNT-Au suggest that tethered [cis-Rh(MMNT)2(CO)2]+Cland (or) Rh(MMNT)(CO)2Cl are the major species at low Rh2Cl2(CO)4loadings, while a new unidentified species predominates at high Rh2Cl2(CO)4loadings. All three catalysts are active 1-hexene hydrogenation catalysts under the mild conditions of 40°C and 1 atm of H2; they are much more active than Au powder or Rh2Cl2(CO)4in solution. Of the three catalysts, RhAu is the most active with a maximum turnover frequency (TOF) of 800 mol H2per mol Rh per min while its turnover (TO) is 29 600 mol H2per mol Rh during a 2-hour run. Under the conditions of 1-hexene hydrogenation, the catalysts lose their CO ligands. Thus, it appears that a form of Rh metal on Au is the catalytically active species.Key words: catalysis, olefin hydrogenation, gold powder, tethered rhodium complexes, infrared studies, adsorption, rhodium complexes.
Synthesis and molecular structures of monooxo aryl complexes of osmium(VI)
Authors: Lau Man-Kit , Chim Joyce LC , Wong Wing-Tak , Williams Ian D , Leung Wa-Hung
Published: April 2011

Reaction of [OsO4] with C7H7MgBr (C7H7 = 2-methylphenyl) followed by column chromatography afforded the reported osmium tetraaryl [Os(C7H7)4] along with the oxo-osmium(VI) ([OsO(C7H7)4]) (1) (13%) and the dioxo-osmium(VI) ([OsO2(C7H7)2]) (2) (25%) complexes. Treatment of [OsO4] with C8H9MgBr (C8H9 = 2,5-dimethylphenyl) gave a mixture of [Os(C8H9)4] (3) (34%) and [OsO(C8H9)4] (4) (4%) while that with C8H9OMgBr (C8H9O = 4-methoxy-2-methylphenyl) afforded [OsO(C8H9O)4] (5) in 20% yield. Oxidation of 3 with 3-chloroperoxybenzoic acid afforded 4 in good yield. The solid-state structures of 1 and 4 have been established by X-ray crystallography. Crystals of 1 are tetragonal with a = 13.080(1) and c = 6.6506(5) Å, V = 1137.9(1) Å3, Z = 2, and space group of P4/n; while those of 4 are tetragonal with a = 13.593(2) and c = 7.377(2) Å, V = 1363.0(5) Å3, Z = 4, and space group of P4/n. The geometry around osmium in both complexes is square pyramidal with the oxo ligand occupying apical position. The OsO and OsC distances in 1 are 1.652(2) and 2.084(1) Å, respectively, while those in 4 are 1.688(7) and 2.088(4) Å, respectively. The cyclic voltammograms of the monooxo aryl osmium(VI) compounds show reversible Os(VI/V) couple at around 1.4 V vs. ferrocene/ferrocenium couple.Key words: osmium(VI), oxo aryl complexes.
In-depth NMR and IR study of the proton transfer equilibrium between [{(MeC(CH2PPh2)3}Ru(CO)H2] and hexafluoroisopropanol
Authors: Bakhmutov Vladimir I , Bakhmutova Ekaterina V , Belkova Natalia V , Bianchini Claudio , Epstein Lina M , Masi Dante , Peruzzini Maurizio , Shubina Elena S , Vorontsov Evgenii V , Zanobini Fabrizio
Published: April 2011

The (carbonyl)dihydride complex [(triphos)Ru(CO)H2] (2) has been synthesized by reaction of the ruthenate [(triphos)RuH3]K (triphos = MeC(CH2PPh2)3) with ethanol saturated with CO. A single crystal X-ray analysis and IR and NMR experiments have shown that 2 adopts in both the solid state and solution an octahedral coordination geometry with a facial triphos ligand, two cis terminal hydrides, and a terminal carbonyl. The reaction of hexafluoro-2-propanol (HFIP) with 2 has been studied in CH2Cl2 solution by IR and NMR spectroscopy. The proton donor interacts with a terminal hydride of 2 forming a rather strong hydrogen bond. The resulting H-bonded adduct [{(triphos)Ru(CO)(H)H}···{HOCH(CF3)2}] (2a) has fully been characterized by in situ NMR and IR techniques. Compound 2a is in equilibrium with the nonclassical η2-H2 complex [(triphos)Ru(CO)H(H2)]+ (2b), which can independently be prepared by protonation of 2 with a strong protic acid at low temperature. Unequivocal characterization of the dihydrogen complex (2b) has been achieved by a multifaceted spectroscopic investigation (Tobs1min = 0.005 s (200 MHz), JH,D [Formula: see text] 30 Hz, DQCC = 78.3 kHz). A combined IR and NMR study of the proton transfer reaction involving 2 and HFIP in CH2Cl2 to give, first, the H-bonded adduct (2a) and, then, the dihydrogen complex (2b) has demonstrated that all these species are in equilibrium in the temperature range from 190 to 260 K. The thermodynamic parameters for the formation of 2a have independently been determined by NMR and IR methods, while those for the formation of 2b have been obtained by IR spectroscopy. An energetic profile for the reaction sequence 2 [Formula: see text] 2a [Formula: see text] 2b is proposed and discussed.Key words: hydrides, hydrogen bonding, ruthenium, IR spectroscopy, NMR spectroscopy.
Potassium borohydride reducing route to phase-pure nanocrystalline InSb at low temperature
Authors: Lu Jun , Xie Yi , Jiang Xuchuan , He Wei , Yan Ping , Qian Yitai
Published: April 2011

The phase-pure III-V binary antimonide (InSb) was first prepared through a novel solution route at a temperature of 200°C: [Formula: see text] Mean crystallite dimensions of 40 nm were determined from X-ray powder diffraction. Transmission electron microscopy images showed that the spherical grains with a diameter of 40-60 nm and the rodlike grains with a size of 120 × 1500 nm coexisted in the same product. The reaction proceeds with indium as the intermediate and a solution-liquid-solid mechanism is proposed for the one-dimensional growth.Key words: indium antimonide, nanorod, phase-pure, solvothermal, solution-liquid-solid mechanism.
A spectrophotometric study of Fe(II)-chloride complexes in aqueous solutions from 10 to 100°C
Authors: Zhao Renhai , Pan Pujing
Published: April 2011

The absorption spectra of Fe(II)-chloride solutions were measured in both the UV (ultraviolet) and near-IR (near infrared) regions at temperatures ranging from 10 to 100°C with chloride concentrations from 0.1 to 16 mol kg-1. The stability constants of all Fe(II)-chloride complexes were derived from the spectra using a non-negative nonlinear least-squares computer program (SQUAD). Earlier work on this system reported in the literature was rigorously reassessed. The activity coefficients of the ionic species were calculated using both the Pitzer model and the Helgeson model. The results obtained with UV and near-IR spectra and with different activity coefficient calculation models are in general agreement. Other useful thermodynamic data, including the Gibbs energies, enthalpies, and entropies for complex formation, were also obtained. It was found that the Fe(II)-chloride complexes gradually undergo a configuration transformation from octahedral to tetrahedral coordination as the temperature and (or) chloride concentration increases. This coordination change is of significant importance to the nuclear reactors, as the presence of the tetrahedral complex can increase the solubility of iron in steam generator crevices.Key words: Fe(II)-chloride complexes, stability constants, solution thermodynamics, spectrophotometry, reactor chemistry.
The syntheses of 6-C-alkyl derivatives of methyl α-isomaltoside for a study of the mechanism of hydrolysis by amyloglucosidase
Authors: Spohr Ulrike , Le Nghia , Ling Chang-Chun , Lemieux Raymond U
Published: April 2011

The epimeric (6aR)- and (6aS)-C-alkyl (methyl, ethyl and isopropyl) derivatives of methyl α-isomaltoside (1) were synthesized in order to examine the effects of introducing alkyl groups of increasing bulk on the rate of catalysis for the hydrolysis of the interunit α-glycosidic bond by the enzyme amyloglucosidase, EC 3.2.1.3, commonly termed glucoamylase (AMG). It was previously established that methyl (6aR)-C-methyl α-isomaltoside is hydrolysed about 2 times faster than methyl α-isomaltoside and about 8 times faster than its S-isomer. The kinetics for the hydrolyses of the ethyl and isopropyl analogs were also recently published. As was expected from molecular model calculations, all the R-epimers are good substrates. A rationale is presented for the catalysis based on conventional mechanistic theories that includes the assistance for the decomposition of the activated complex to products by the presence of a hydrogen bond, which connects the 4a-hydroxyl group to the tryptophane and arginine units. It is proposed that activation of the initially formed complex to the transition state is assisted by the energy released as a result of both of the displacement of perturbed water molecules of hydration at the surfaces of both the polyamphiphilic substrate and the combining site and the establishment of intermolecular hydrogen bonds, i.e., micro-thermodynamics. The dissipation of the heat to the bulk solution is impeded by a shell of aromatic amino acids that surround the combining site. Such shields are known to be located around the combining sites of lectins and carbohydrate specific antibodies and are considered necessary to prevent the disruption of the intermolecular hydrogen bonds, which are of key importance for the stability of the complex. These features together with the exquisite stereoelectronic dispositions of the reacting molecules within the combining site offer a rationalization for the catalysis at ambient temperatures and near neutral pH. The syntheses involved the addition of alkyl Grignard reagents to methyl 6-aldehydo-α-D-glucopyranoside. The addition favoured formation of the S-epimers by over 90%. Useful amounts of the active R-isomers were obtained by epimerization of the chiral centers using conventional methods. Glycosylation of the resulting alcohols under conditions for bromide-ion catalysis, provided methyl (6aS)- and (6aR)-C-alkyl-hepta-O-benzyl-α-isomaltosides. Catalytic hydrogenolysis of the benzyl groups afforded the desired disaccharides. 1H NMR studies established the absolute configurations and provided evidence for conformational preferences.Key words: amyloglucosidase (AMG), exo-anomeric effect, 6-C-alkyl-α-D-glucopyranosides and isomaltosides, mechanism of enzyme catalysis.
Factors limiting oxygen delignification of kraft pulp
Authors: Akim Leonid G , Colodette Jorge Luiz , Argyropoulos Dimitris S
Published: April 2011

Softwood kraft pulp was subjected to a laboratory one- and three-stage oxygen delignification process. Pulp and liquor samples were collected at different stages of the process with particular attention being paid to the early and late stages. A novel residual lignin isolation method extracted about 65% of the oxidized residual lignins at a purity exceeding 90%. Using this methodology coupled to quantitative31P NMR,13C NMR, 2D heteronuclear (HMQC) NMR spectroscopic and analytical pyrolysis techniques allowed a thorough characterization of the residual and solubilized lignin fractions at the various stages of the process. Our conclusions do not point to a single factor as being responsible for the limits confronting oxygen delignification. Amongst the major factors impeding the effectiveness of oxygen delignification are: (i) the accumulation of relatively inert 5,5' biphenyl structures originally present in kraft lignin from dibenzodioxocin ring opening reactions; and (ii) the accumulation of considerably less reactive p-hydroxyphenyl structures. Detailed quantitative information was obtained and discussed in relation to the presence and role of these unreactive phenolic fractions on the residual oxidized lignins. As such we arrived at important conclusions as to why and how these structures remain and accumulate on the fiber. In addition, issues related to the profiles of the total phenolic hydroxyl content of the residual lignins and the remaining arylglycerol β-O-4 structures are discussed.Key words: analytical pyrolysis, biphenyl structures, HMQC, NMR, oxidation mechanism, oxygen delignification, p-hydroxyphenyl moieties, quantitative13C NMR, quantitative31P NMR, residual lignin, solubilized lignin, total phenolic hydroxyls.
Gaussian basis sets for the atoms from K through Xe
Authors: Centoducatte R , de Castro E VR , Jorge F E
Published: April 2011

An improved generator coordinate Hartree-Fock (IGCHF) method is used to generate Gaussian basis sets for the atoms from K (Z = 19) through Xe (Z = 54). The Griffin-Hill-Wheeler-HF equations are integrated using the integral discretization technique. The ground state HF total energies obtained by us are compared with those calculated with the original GCHF method and with other approaches reported in the literature. The largest difference between our energy values and the corresponding ones computed with a numerical HF method is equal to 6.003 mhartree for Kr (Z = 36).Key words: improved generator coordinate Hartree-Fock method, Gaussian basis sets, total energies.
One-electron reduction of the γ*-isomer of [S2W18O62]4leads to isolation of the α-isomer
Authors: Richardt Peter JS , White Jonathon M , Tregloan Peter A , Bond Alan M , Wedd Anthony G
Published: April 2011

Bu4N+salts of [S2W18O62]5and [S2W18O62]6can be isolated by electro reduction of γ*-(Bu4N)4[S2W18O62] in MeCN. α-(Bu4N)5[S2W18O62]·4MeCN crystallizes in space group C2/c with a = 26.226(2) Å, b = 15.570(2) Å, c = 38.407(2) Å, β = 115.59(2)°, V = 14 145(2) Å3, and Z = 8. The observations indicate that a γ* « α isomerization is associated with the [S2W18O62]4 [S2W18O62]5couple. However, the transformation could not be detected on the timescale of cyclic voltammetry up to a scan rate of 10 V s1. The available data suggest that either: (i) the γ* « α equilibrium favors one of the isomers in solution for both redox states, or (ii) the isomerization is slow on the cyclic voltammetric timescale but the differences in E1/2values for the α-[S2W18O62]4[S2W18O62]5and γ*-[S2W18O62]4[S2W18O62]5couples cannot be resolved by cyclic voltammetry.Key words: polyoxometalates, synthesis, electrochemistry, isomerization.
On the reduction of rhodium trichloride in the presence of triisopropylphosphine
Authors: Butler David CD , Bruce Duncan W , Lightfoot Philip , Cole-Hamilton David J
Published: April 2011

The reduction of RhCl3·3H2O by sodium amalgam in the presence of P-i-Pr3 has been reexamined. Reaction of RhCl3·3H2O with P-i-Pr3 in THF gives i-Pr3PO and [RhHCl2(P-i-Pr3)2] or [RhDCl2(P-i-Pr3)2] if D2O is added. Further reaction of [RhHCl2(P-i-Pr3)2] with P-i-Pr3 gives [i-Pr3PH][RhHCl3(P-i-Pr3)2], which reversibly dissociates to [RhHCl2(P-i-Pr3)2] and [i-Pr3PH]Cl at high temperatures in solution. Sodium amalgam reduction of [RhHCl2(P-i-Pr3)2] in THF containing P-i-Pr3 gives [RhH(P-i-Pr3)3] if water is rigorously excluded, but [RhH2Cl(P-i-Pr3)2] if water is present.Key words: rhodium, trisiopropylphosphine, hydride, reduction.
The versatile reactivity of 2-aryl-4,6-dinitrobenzotriazole 1-oxides in Diels-Alder type condensations and in σ-complexation - A relationship between superelectrophilicity and pericyclic reactivity
Authors: Vichard Dominique , Boubaker Taoufik , Terrier François , Pouet Marie-José , Dust Julian M , Buncel Erwin
Published: April 2011

A two-pronged study of a series of 2-aryl-4,6-dinitrobenzotriazole 1-oxide substrates (2ac) is reported: DielsAlder type pericyclic reactivity and covalent hydration to yield Meisenheimer type hydroxy anionic σ-adducts. The most activated benzotriazole 1-oxide 2a is found to exhibit both dienophilic and heterodienic behaviour on treatment with cyclopentadiene, providing a highly functionalized stereoselective diadduct (7). This diadduct is shown to be the result of two consecutive inverse demand DielsAlder condensations proceeding through the endo mode with a trans addition of two cyclopentadiene molecules. Kinetic and thermodynamic measurements of the ease of covalent hydration of 2ac to give σ-adducts 4ac in aqueous solution indicate that the electrophilic reactivity of the 4,6-dinitrobenzotriazole 1-oxide structure is much closer to that of the superelectrophilic 4,6-dinitrobenzofuroxan (DNBF, 1a) than that of the standard Meisenheimer electrophile 1,3,5-trinitrobenzene (TNB). The pKa values range from 6.70 for the 2-(2',4',6'-trinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide (Pi-DNBT, 2a) to 10.73 for the 2-phenyl-4,6-dinitrobenzotriazole 1-oxide (Ph-DNBT, 2c). The observation that the most activated benzotriazole 1-oxide structure 2a which resembles 4,6-dinitrobenzofuroxan (DNBF) in superelectrophilic behaviour, is the only one that undergoes DielsAlder reactions, points to a direct relationship between superelectrophilic and pericyclic reactivity.Key words: σ-complexes, arylnitrobenzotriazole 1-oxides, super-electrophiles, DielsAlder condensations, pericyclic reactions.
N,N-dimethylhydroxamidovanadium(V). Interactions with sulfhydryl-containing ligands: V(V) equilibria and the structure of a V(IV) dithiothreitolato complex
Authors: Bhattacharyya Sudeep , Martinsson Anette , Batchelor Raymond J , Einstein F WB , Tracey Alan S
Published: April 2011

The major aqueous equilibrium complexation reactions of vanadate in the presence of N,N-dimethylhydroxylamine (DMHA) and with dithiothreitol (DTT), β-mercaptoethanol, glycine, or cysteine in solution have been studied using 51V NMR spectroscopy. Previously unreported DMHA complexes of 2:1 and 2:3 V:DMHA stoichiometry were observed and characterized. Concentration studies showed that, for the three sulphur-containing ligands, the major product of sulphur coordination has a 1:2:1 stoichiometry of vanadate to dimethylhydroxylamine to heteroligand. These products do not carry a charge in neutral to moderately basic solution. A second product type of 1:1:1, V to DMHA to heteroligand, stoichiometry is also formed. These products carry a single negative charge. A reductive reaction between vanadate and excess DTT to form a V(IV) complex was also observed and a solid product was isolated. This product could also be obtained by direct reaction of vanadyl sulphate with DTT. It was characterized by X-ray diffraction studies. Crystal structure of [{VO(SCH2CHOHCHOCH2S)}2] [AsPh4]2: monoclinic, space group P21/n, Z = 2, a = 10.1607(18) Å, b = 17.8255(42) Å, c = 15.1520(33) Å, β = 104. 000(15)°, V = 2662.8 Å3, RF = 0.038 for 2327 data (Io [Formula: see text] 2.5σ(Io)) and 325 variables.Key words: vanadate, vanadyl, dithiothreitol, mercaptoethanol, cysteine, glycine, equilibrium constants, crystal structure, X-ray, vanadium NMR.
Kinetic modeling of homogeneous methanol synthesis catalyzed by base-promoted nickel complexes
Authors: Mahajan Devinder , Krisdhasima Viwat , Sproull Robert D
Published: April 2011

Nickel complexes promoted by alkoxide bases can affect facile conversion of synthesis gas into methanol under thermodynamically favorable temperatures. At 100°C, syngas conversion of 99% with turnover frequency of 66 h-1 is reported. The reaction is truly catalytic in Ni as well as in base. A kinetic study of the Ni(CO)4-KOMe catalyst system in 1,2-bis(2-methoxy ethoxy)ethane (triglyme)-MeOH solvent mixture is presented. The kinetic expression includes terms of zero-order in H2 and first-order in CO with syngas of H2-CO stoichiometry of ~2:1 and less than first-order in Ni (0.03-0.10 M), ~third-order in base (2.0-4.75 M), and an exponential dependence on methanol concentration (13.0-23.7 M at 2.0 M base; 15.8-22.6 M at 3.0 M base). The activation energy of 42.2 kJ mol-1 was estimated from the Arrhenius plot of the data between 374 and 393 K. Gas phase IR spectrum at the end of each run showed an intense signature peak at 2060 cm-1 for Ni(CO)4. Process uncertainties to commercialization of this versatile homogenous catalyst system for CO hydrogenation to methanol are discussed.Key words: homogeneous catalysis, syngas conversion, methanol synthesis, alkoxides, carbonyls of nickel.
Highly efficient and stable catalyst for peroxynitrite decomposition
Authors: Geletii Yurii V , Bailey Alan J , Cowan Jennifer J , Weinstock Ira A , Hill Craig L
Published: April 2011

The new cobalt substituted-polyoxometalate K7[CoAlW11O39]·15H2O and the simple CoCl2·6H2O salt are efficient catalysts for peroxynitrite decomposition. These compounds also catalyze the oxidation of ascorbic acid and the nitration of phenol by peroxynitrite.Key words: peroxynitrite, polyoxometalates, antioxidant.
A novel coordination mode for a pyridylphosphine ligand. X-ray structures of [RuCl2(NO)L] (I) and [RuCl2(NO)L]·DMSO (II) (L = [(2-py)2PC2H4POO(2-py)2]-)
Authors: Batista Alzir A , Queiroz Salete L , Healy Peter C , Buckley Robbie W , Boyd Sue E , Berners-Price Susan J , Castellano Eduardo E , Ellena Javier
Published: April 2011

The ruthenium(II) complex, [RuCl2(NO)L] (I), (L = [(2-py)2PC2H4PO2(2-py)]-) was obtained from recrystallization of RuCl3NO(d2pype) (d2pype = (2-py)2PC2H4P(2-py)2) in the presence of HNO3, crystallizing in the monoclinic space group P21 (no. 4), with a = 8.012(4) Å, b = 14.454(4) Å, c = 9.353(3) Å, β = 105.77(3)°, and Z = 2. Crystals of the DMSO solvate of the complex (II) were obtained from (CD3)2SO solution, crystallizing in the monoclinic space group P21/c (no.14) with a = 9.7080(2) Å, b = 22.2920(5) Å, c = 11.5230(3) Å, β = 92.0450(10)°, and Z = 4. In both complexes, the geometry about the ruthenium atom is a distorted octahedron mainly as a result of the tridentate [P,N,O]-bonding mode of L. The ν (NO) bands at 1875 cm1 in both complexes are consistent with the linear disposition of the NO group and the Ru atom as is observed in the X-ray crystal structure (Ru-N1-O1 angle = 178.5(4)°).Key words: pyridylphosphine, nitrosyl, ruthenium complex, X-ray structure.
Functionalization vs. degradation of 1,4-polybutadiene by ruthenium complex catalyzed reaction with vinylsilanes
Authors: Marciniec Bogdan , Malecka Ewa , Gulinski Jacek , Grundwald-Wyspianska Monika , Lewandowski Mariusz
Published: April 2011

Polybutadiene (I) containing 91% of 1,4-(cis-trans) units and 9% of 1,2-units in the presence of vinyltriethoxysilane (II) and ruthenium catalysts RuCl2(PPh3)3 (III), RuHCl(CO)(PPh3)3 (IV), and [RuCl2(CO)3]2 (V) at 100-130°C undergoes functionalization and (or) partial degradation as an effect of competitive silylative coupling of =C-H and cross-metathesis of I with II. Significant degradation of I occurs at lower temperatures (100-110°C) (particularly when the process is carried out in air), but exclusive functionalization of I is observed at higher temperature (120-130°C) regardless of the atmosphere (air or argon) used.Key words: functionalization, degradation, polybutadiene, ruthenium complexes.
Synthesis, spectroscopic characterization, and structural studies of new Cu(I) and Cu(II) complexes containing organophosphorus ligands, and crystal structures of (Ph3P)2Cu[S2PMe2], (Ph3P)2Cu[(OPPh2)2N], Cu[(OPPh2)2N]2, and Cu[(OPPh2)(SPPh2)N]2
Authors: Silvestru Anca , Rotar Adina , Drake John E , Hursthouse Michael B , Light Mark E , Farcas Sorin I , Rösler Roland , Silvestru Cristian
Published: April 2011

The Cu(I) complexes, (Ph3P)2CuL (L = [S2PMe2]-, [OSPR2]- (R = Me, Ph), [(XPR2)(YPR'2)N]- (X, Y, R, R' = O, O, Ph, Ph; O, S, Ph, Ph; O, S, OEt, Ph; S, S, Me, Me)) and Cu(II) complexes, CuL2 (L = [(XPR2)(YPR'2)N]- (X, Y, R, R' = O, O, Ph, Ph; O, S, Ph, Ph)), have been prepared. The Cu(I) derivatives were characterized by multinuclear NMR spectroscopy and in two cases by X-ray crystallography. (Ph3P)2Cu[S2PMe2] (1) crystallizes in the orthorhombic space group P212121 (No. 19) with cell parameters a = 9.782(2), b = 17.808(4), c = 20.216(4) Å, V = 3521(6) Å3 and Z = 4, and (Ph3P)2Cu[(OPPh2)2N] (4) in the triclinic space group P[Formula: see text] (No. 2) with cell parameters a = 9.8079(2), b = 12.9141(3), c = 22.5666(5) Å, α = 75.714(2), β = 79.465(2), γ = 68.2770(8)°, V = 2559.9(1) Å3 and Z = 2. In both cases the phosphorus ligands are bidentate, thus resulting in monomeric molecules that contain tetrahedral CuP2S2 and CuP2O2 cores. The molecular structures of two of the Cu(II) derivatives were also determined. Cu[(OPPh2)2N]2 (8) and Cu[(OPPh2)(SPPh2)N]2 (9) crystallize in the triclinic space group P[Formula: see text] (No. 2) with cell parameters a = 8.887(2), b = 10.739(2), c = 12.477(3) Å, α = 77.61(3), β = 76.15(5), γ = 79.46(3)°, V = 1118.3(4) Å3 and Z = 1 for 8, and a = 9.626(2), b = 14.151(3), c = 24.752(5) Å, α = 88.23(3), β = 79.93(3), γ = 89.77(3)°, V = 3181(1) Å3 and Z = 3 for 9. The molecule of Cu[(OPPh2)2N]2 (8) has a planar CuO4 core, while in Cu[(OPPh2)(SPPh2)N]2 (9) both planar and tetrahedral copper cores are observed in a ratio of 1:2.Key words: structure, copper, thiophosphinates, oxo- and thio-imidodiphosphinates
Determination of the complexation properties of a crosslinked poly(acrylic acid) gel with copper(II), nickel(II), and lead(II) in dilute aqueous solution
Authors: Morlay Catherine , Mouginot Yolande , Cromer Monique , Vittori Olivier
Published: April 2011

The possible removal of copper(II), nickel(II), or lead(II) by an insoluble crosslinked poly(acrylic acid) was investigated in dilute aqueous solution. The binding properties of the polymer were examined at pH = 6.0 or 4.0 with an ionic strength of the medium µ = 0.1 or 1.0 M (NaNO3) using differential pulse polarography as an investigation means. The highest complexing capacity of the polyacid was obtained with lead(II) at pH = 6.0 with µ = 0.1 M, 4.8 mmol Pb(II)/g polymer. The conditional stability constants of the complex species formed were determined using the method proposed by Ruzic assuming that only the 1:1 complex species was formed; for lead(II) at pH = 6.0 and µ = 0.1 M, log K' = 5.3 ± 0.2. It appeared that the binding properties of the polymer increased, depending on the metal ion, in the following order: Ni(II) < Cu(II) < Pb(II). The complexing capacity and log K' values decreased with the pH or with an increase of the ionic strength. These results were in agreement with the conclusions of our previous studies of the hydrosoluble linear analogues. Finally, with the insoluble polymer, the log K' values were comparable to those previously obtained with the linear analogue whereas the complexing capacity values expressed in mmol g-1 were slightly lower.Key words: insoluble crosslinked poly(acrylic acid), copper(II), nickel(II), and lead(II) complexation.
Tautomerization tendencies of 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, and cyclic β-keto esters of five- and six-membered rings
Authors: Rojas Antonio , Perez-Encabo Alfonso , Herraiz-Sierra Ignacio , Blanco Carlos A
Published: April 2011

NMR and kinetics studies of the tautomeric equilibrium of 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, and methyl 2-oxocycloalkanecarboxylates of five- and six-membered rings have been carried out. By comparing 1H NMR and 13C NMR spectra recorded in D2ODOCD3 and CDCl3, with those results derived using a bromination kinetic procedure in dilute aqueous solution, information concerning tautomeric interconversion is provided. Some discussions considering ionisation equilibria and rate constants involved have also been considered. Solvent and concentration effects on keto-enol equilibria have also been discussed.Key words: 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, methyl 2-oxocycloalkanecarboxylates, equilibrium, tautomerization, ionization.
Excess enthalpies of the ternary mixtures: ethyl tert-butylether + n-heptane + (n-decane or n-dodecane) at 298.15 K
Authors: Wang Zhaohui , Horikawa Yoshiteru , Benson George C , Lu Benjamin C
Published: April 2011

Excess molar enthalpies, measured at 298.15 K in a flow microcalorimiter, are reported for the two ternary systems, ethyl tert-butylether + n-heptane + n-decane and ethyl tert-butylether + n-heptane + n-dodecane. Smooth representations of the results were used to construct constant enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the LiebermannFried model using only the physical properties of the components and their binary mixtures.Key words: excess enthalpies, ternary mixtures, ethyl tert-butylether, n-alkanes, LiebermannFried model.