Ammonia chemical ionization mass spectrometry of alcohols: Structural,stereochemical, molecular-size and temperature effects

Ammonia chemical ionization (CI) mass spectra of various open-chain, cyclic and unsaturated C₅- to C₁₀-alcohols were obtained at source temperatures ranging from 60° to 250°C. The reactivity of the ammonia adduct ion MNH and its fragmentation channels are characteristic for substrate structure. Although strongly temperature-dependent, the spectra give nevertheless information on the OH-group environment as well as on the C-skeleton at any source temperature. Primary, secondary and tertiary alcohols as well as allylic and simple olefinic alcohols can be distinguished by their spectra, which show ammonium adduct ions [MNH₄]⁺, adduct dehydrogenation ions [MNH₄-H₂], ammonium substitution ions [MNH₄-H₂O]⁺ and [M-OH]⁺-ions as the main characteristic peaks. Moreover, konfigurational assignments of stereoisomeric alcohols are possible for larger substrate-size and source-temperature ranges than with isobutane CI mass spectrometry. Homologous M NH-ions show molecular-size control of fragmentation and linear MNH-ions are less stable than branched isomers due to incomplete energy randomization.     

Salting-out thin-layer chromatography of transition metal complexes. IV: Effect of sorbent on the behaviour of mixed aminocarboxylato cobalt (III) complexes

Summary From literature data for 14 mixed aminocarboxylato cobalt(III) complexes, the effect of the sorbent on R_M values, salting-out efficiency (m) and separation factors () of adjacent members of homologous series was investigated in salting-out, thin-layer chromatography on silica gel, polyacrylonitrile and cellulose sorbents, using ammonium sulphate solutions as developers. For complexes belonging to the same homologous series, linear dependence was found between R_M,m and log values, respectively, on two different sorbents. Polyacrylonitrile was shown to be the most suitable sorbent for the separation of the complexes since it gave the highest values for R_M,m and .     

Cation exchange column chromatography in aqueous ammonium acetate: Separation of U(VI), Al(III), Sr(II), Ba(II) and Hg(II) from other metal ions

Summary A rigorous analysis of the effect of various concentrations (0.02–1.60M) of ammonium acetate on the distribution coefficients (K) of a number of metal ions using cation exchanger Dowex 50W-X8 (100–200 mesh NH₄ ⁺-form) has been made. On account of the low affinity of U(VI) for resin in 0.20M NH₄OAc it can be separated from all other metal ions. HighK values of Sr(II), Ba(II) and Hg(II) at higher 0.50M NH₄OAc are responsible for their separation from others. The abnormal column Chromatographic behaviour of Al(III) permits its separation from other metal ions including U(VI), Sr(II), Ba(II), Hg(II). A number of binary and ternary separations have been achieved.     

Room temperature phosphorescence optosensing for gadolinium

An optosensing method for gadolinium based on the room-temperature phosphorescence behavior in aqueous solution induced by the transient adsorption of the complex formed by 1,4-bis (1-phenyl-3-methyl-5-pyrazolone-4-)butanedione (1,4) with Gd (III) on the chelating resin Chelex 100 (packed in a flow cell) is proposed. The proposed optosensing is satisfactory for the determination of the gadolinium ion in the range 8 × 10^–7–5 × 10^–5 M with a correlation coefficient of 0.995. The relative standard deviation was 2.0% for determination of 5× 10^–6 M gadolinium ion (n = 10). The response mechanism of the optosensing and the interferences of other lanthanide ions were also investigated. The method has been used to determine gadolinium ion in synthetic sample.     

Tetramethylammonium-calcium-triazid. Darstellung und Kristallstruktur

[N(CH₃)₄]Ca(N₃)₃,M=240.29, was prepared from aqueous solutions of tetramethylammoniumazide with calciumazide at 298 K. The crystals are tetragonala=936.6(7) pm,c=694.7(5)pm, space group P4/nmm,Z=2, (x)=1.31Mgm^–3. The crystal structure was determined by single crystal x-ray diffraction (234 Mo-K-reflections, =0.469 mm^–1,R=0.064). Calcium is octahedrally coordinated to six azide groups. The octahedra are connected via azide groups to a threedimensional array with the complex ammonium ions between. The terminal nitrogen atoms of the azide groups and the methyl groups are considerably disordered.

     

Mechanism of catalytic ascorbic acid oxidation system Cu2+–ascorbic acid–O2

Analysis is made of reported results on the kinetics and mechanism of ascorbic acid oxidation with oxygen in the presence of cupric ions. The diversities due to methodological reasons are cleared up. A kinetic study of the mechanism of Cu²⁺ anaerobic reaction with ascorbic acid (DH₂) is carried out. The true kinetic regularities of catalytic ascorbic acid oxidation with oxygen are established at 2.7 ≤ pH < 4, 5 × 10^?4 ≤ [DH₂] ≤ 10^?2M, 10^?4 ≤ [Cu²⁺] ≤ 10^?3M, and 10^?4 ≤ [O₂] ≤ 10^?3M: where??₁ (25°C) = 0.13 ± 0.01 M^?0.5˙sec^?1. The activation energy for this reaction is E₁ = 22 ± 1 kcal/mol. It is found by means of adding Cu⁺ acceptors (acetonitrile and allyl alcohol) that the catalytic process is of a chain nature. The Cu⁺ ion generation at the interaction of the Cu²⁺ ion with ascorbic acid is the initiation step. The rate of the chain initiation at [Cu²⁺] ± 10^?4M, [DH₂] ± 10^?2M, 2.5 < pH < 4, is where??_i,1 (25°C) = (1.8 ± 0.3)M^?1˙sec^?1, E_i,1 = 31 ± 2 kcal/mol. The reaction of the Cu⁺ ion with O₂ is involved in a chain propagation, so that the rate of catalytic ascorbic acid oxidation for the system Cu²⁺? DH₂? O₂ is where??₁ (25°C) = (5 ± 0.5) × 10⁴ M^?1˙sec^?1. The Cu⁺ ion and a species interacting with ascorbate are involved to quadratic chain termination. By means of photochemical and flow electron spin resonance methods we obtained data characteristic of the reactivities of ascorbic acid radicals and ruled out their importance for the catalytic chain process. A new type of chain mechanism of catalytic ascorbic acid oxidation with oxygen is proposed: .     

On “Coordinational Stabilization” of High Oxidation States of Metals

A hypothesis of the ligand matrix stabilization of metal ions in high oxidation states is considered using the structural thermodynamic model and stabilization of Zr⁴⁺ ion in ZrC₆₀ cluster as an example. The corresponding energy estimates are presented for fullerides of the M ^z @C _m M ^s type (m 60). The possibility of using fullerenes as matrices with a high electron affinity is shown.     

Determination of cobalt,molybdenum and vanadium in austrian mineral waters by ICP-AES after ion-exchange separation and preconcentration

A method is described for the determination of cobalt, molybdenum and vanadium in mineral water samples by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) after separation of these elements from the matrix by ion exchange. The samples are acidified with concentrated hydrochloric acid (10 ml/l) and the elements are adsorbed as thiocyanate complexes. Elution is performed with a mixture 2M in perchloric acid and 1M in hydrochloric acid and subsequently with 1M hydrochloric acid. After evaporation of the eluates and dissolution of the residue the volume of the measuring solution for ICP-AES is 10 ml. The recoveries for Co, Mo and V at a concentration level of 1 g/1 in mineral waters were approximately 99%. A concentration factor of 100 is achieved by this procedure.     

Synthesis and chemistry of dimetallacyclic compounds: Utility ofM(CO)4(η2-alkyne) (M=Ru,Os) building blocks

Low temperature photolysis ofM(CO)₅ (M=Ru, Os) provides efficient synthesis for a variety ofM(CO)₄(²-alkyne) derivatives. The molecules show surprising reactivity toward other 18-electron transition metal carbonyl compounds (M(CO)₅ and CpM(CO)₂,M=Co, Rh, Ir) to give homo- and heterodimetallacyclic complexes. The general features of the condensation reactions are described, the structures of the compounds discussed, and a few illustrative examples of the transformation of the bridging organic units given.     

The solubility of cellulose in liquid ammonia/ammonium thiocyanate solutions: Thermoreversible gelation and a preliminary report on fiber formation

The melting temperatures of thermoreversible gels formed from solutions of cellulose in liquid ammonia/ammonium thiocyanate mixtures were measured over a volume fraction range of .01–.004. Three samples of cellulose with M_w ranging from 1 × 10⁵ to 1.64 × 10⁵ were used. The findings show that the structural makeup of the gels is strongly reflected in their time-dependent behavior. The reciprocal of their melting temperature is a nearly linear function of the logarithm of the cellulose concentration. The relation between the logarithm of M_w and the reciprocal temperature of gel melting was also nearly linear. Exothermic heats of reaction ranging from 150 to 460 kcal/mol were calculated from the Ferry-Eldridge relationship (? ln C/?) = ΔH_x/R for the formation of cross-links, assuming that they result from a binary association of chains. It is inferred that the cross-linking loci in the gel were crystallites that consisted of glucose units. In addition, an initial study is reported of the fiber-forming potential of the liquid ammonia/ammonium thiocyanate system. Rudimentary fiber extrusion from a modified syringe was readily demonstrated. Operable coagulation systems involved proton-donating agents as well as methanol. Tenacities of these unstretched, as spun fibers, ranged as high as 0.89 g/d.     

Molecular recognition as shown by the solvent extraction of (R)- and (S)-[α-(1-naphthyl)ethyl] ammonium picrate or orange 2 by chiral pyridino-crown ethers

A solvent extraction technique was used to determine equilibrium constants for the reactions occurring when an aqueous phase containing [-(1-naphthyl)ethyl]ammonium ions [(R)- and (S-isomers] is equilibrated with a chloroform phase containing chiral substituted pyridino-18-crown-6 ligands. Selectivity coefficients and equilibrium constants for the interactions in chloroform solutions were calculated. The existence of two different types of ion pairs separated by the macrocycle molecule was detected from the UV spectra. One ion pair has a nearly complete separation of the picrate anion from the protonated amine by the ligand. The other has the picrate ion only partly separated from the cation by the macrocycle.     

Infrared spectral studies of ion association in nonaqueous solutions of cyanide salts with consequences for their nucleophilic reactivity

An infrared spectrometric study of alkali metal and tetraphenylarsonium cyanide (As ⁴ CN) solutions in DMSO or DMF shows that even for concentrations of 0.1M a large proportion of the ions are associated. The order of basicity established through methanol (OH) frequency shifts is CN^–>Cl^–>Br^–. Addition of common ions or cyclic polyether to these solutions, as well as correlations between the (CN^–) frequencies and those of the (CN) bands of CH₃CN bonded to the same cations, suggests assignments of the observed bands to solvated contact ion pairs M⁺ CN^–, triple ions M⁺ CN^– M⁺, and aggregates (M⁺ CN) _n ^– . The nucleophilic reactivity of these salts is related to the structure of these solutions.This article is taken in part from the thesis of A. Loupy, University Paris-Sud Orsay, April 9, 1975, CNRS thesis order No. AO 10102.     

Electronic Structures, (d-p)π Conjugation Effects, and Spectroscopic Properties of Polyoxometalates: M6O19 2− (M=Cr, Mo, W)

The electronic structures and bonding of isopoly oxometalates M₆O₁₉ ^2– (M=Cr, Mo, W) have been investigated by using ab initio and relativistic density functional methods. We have discussed the role of the central oxygen atom and the (d-p) conjugation interactions between the metal and bridging oxygen atoms. It is found that there exist 12 three-centered two-electron (d-p-d) bonds for the three M₄(-O)₄ planar rings in M₆O₁₉ ^2– ions and these hexametalates are considered to have quasi-aromaticity. The (d-p) conjugation effects play essential role in stabilizing these cluster compounds, and the reduced (d-p) conjugation effects account for the instability of the isopoly oxochromate ion, Cr₆O₁₉ ^2–. The vibrational spectra and electronic spectra of M₆O₁₉ ^2– ions are evaluated and assigned theoretically and the calculated spectra are in fairly good agreement with the measured experimental results.     

Ionic interaction behavior and facilitated olefin transport in poly(n‐vinyl pyrrolidone):Silver triflate electrolytes; Effect of molecular weight

Interactions of cation/anion and cation/polymer in poly(N‐vinyl pyrrolidone) (PVP):silver triflate (AgCF₃SO₃) electrolytes with different weight‐average molecular weights (M_w's) of 1 × 10⁶ (1 M), 3.6 × 10⁵ (360 K), 4 × 10⁴ (40 K), and 1 × 10⁴ (10 K) have been studied with IR and Raman spectroscopies. According to the change of the C?O peak, coordination of silver ions by C?O in a low M_w (10 or 40 K) PVP matrix tend to be always thermodynamically favorable than high M_w (1 M or 360 K) PVP, demonstrating that the polymer matrix of low M_w dissolves silver salts more effectively. In addition, silver cations interact with both larger SO and smaller CF₃ to form ion pairs, and the former interaction is stronger than the latter in a monomer or low M_w polymer matrix (40 K, 10 K), as demonstrated by theoretical ab initio calculation or experimental spectroscopy, respectively. However, CF₃ interacts more favorably with silver cation than SO in high M_w (1 M and 360 K) PVP, which is ascribed to the steric effect of the bulky SO anion by highly entangled polymer chains. Despite the superior dissolving property of the low M_w polymer matrix, the membranes consisting of low M_w PVP and AgCF₃SO₃ exhibited poor separation performance for propylene/propane mixtures in comparison with those of high M_w, presumably because of the poor mechanical property for membrane formation in low M_w PVP. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1813–1820, 2002     

Mass-spectral Study of 9-[α(β,γ)-Picolylidene]-1(4)-azafluorenes

A mass-spectral study was carried out on the behavior of the Z- and E-isomers of 9-picolylideneazafluorenes. A possible mechanism for the elimination of a hydrogen atom from the M⁺ ion of the Z- and E-isomers of 1(4)-azafluorene derivatives was examined. Mass spectrometry permitted a distinction between compounds isomeric relative to the position of the nitrogen atom in the azafluorene fragments and also the Z- and E-isomers of picolylidene derivatives of 1- and 4-azafluorenes possessing - and -pyridyl substituents.     

Determination of Nitrogen in Silicon Carbide by Secondary Ion Mass Spectrometry

The emission of atomic and complex nitrogen ions, which are the main impurity determining the n type conduction of silicon carbide, is investigated. It is shown that, among all the secondary ions of the C _x N and Si _x N kind (x = 0, 1, 2, 3), the ²⁶(CN)^– fragment exhibits the highest ion yield. The use of an ion peak with a specified mass as an analytical signal provides a detection limit for nitrogen in SiC at a level of 10¹⁶ cm^–3. This result is attained in measurements at high mass resolution (M/M = 7500, interference peak ²⁶(¹³C₂)^–).     

Fullerides: heterometallic superconductors with composition M<Subscript>2</Subscript>M′C<Subscript>60</Subscript> (M = K,Rb; M′ = Yb,Lu, Sc)

One- or two-step reactions of potassium and rubidium fullerides with composition M_k C₆₀ (M = K, Rb; k = 3—6) and K₆C₆₀ + m K mixtures (m = 1, 3) with anhydrous salts MCl₃ (M = La, Pr, Nd, Sm, Gd, Tb, Yb, Lu, Y, Sc) and YbI₂ in a toluene—THF medium afforded heterometallic fullerides M_3–nM_nC₆₀ (n = 1—3). Among these compounds, substituted fullerides with composition M₂MC₆₀ (M = Yb, Lu, Sc) display superconducting properties with critical temperatures of 14—20 K.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1623–1628, August, 2004.     

SIMS yields from glasses; secondary ion energy dependence and mass fractionation

SIMS studies of glasses indicate that calibration of positive monatomic ion yields via relative sensitivity factors (RSF) is significantly dependent both on the kinetic energyE _k and on the massM _t of the analyzed ions. Due to elemental differences in the energy distributions of the sputtered ions, relative emissivities at highE _k are radically different from those at the tops of the distributions. While the RSF values of cations from glasses range within ca. 3 powers of ten, atE _k above ca. 40 eV the range remains within a factor of ten or less, and further change of relative elemental sensitivities withE _k is slow. At low exit energy the LTE formalism is reasonably well obeyed. At highE _k , a trend is noted towards a relative suppression of the ion yields of lowvalent elements.Measurements of isotope fractionation in secondary ion yield were performed on 17 elements sputtered from glasses. The mass factor (defined by the proportionality of the yield toM _i ^– ) is found to range from near-zero to2.5, dependent on the element and onE _k . For most elements a drops steeply at lowE _k , but generally a slow rise is noted at higher energies. The behaviour of appears to be to some extent connected with the shape of the energy distribution curve. The dependence of onE _k and on elemental parameters can qualitatively be described in terms of a simple phenomenological model.     

Creatinine in Serum and Plasma Direct Microdetermination by Kinetics

Abstract

A kinetic method for the determination of creatinine in 50 ul of serum or plasma, without deproteinization or pre-treatment, at rate of 50 to 100 samples an hour is described. The precision is better than 2% (CV) in the normal range and the recovery very close to 100%. The method is linear at least up to 10^?3 M (11.3 mg/lOOml) and can be standardized with aqueous creatinine solutions. Glucose and proteins do not interfere with the reaction.     

Analysis of the Probability of the Mössbauer Effect in Iron(III) β-Diketonates

The probability of the Mössbauer effect f has been evaluated and the Debye temperatures of intermolecular vibrations _M at 295 and 78 K have been determined for ten Fe(III) -diketonates, which are complexes of molecular type. Variation of _M with temperature and molecular mass M has been found; in the latter case, _M decreases as M increases. As a result of this antibatic change in _M and M, the effect of a decreased energy of intermolecular interaction dominates the effect of increased molecular mass, and f decreases in conformity with the prediction provided by the molecular crystal model.