On some controversy regarding νOH assignments in CsH2PO4

Spectroscopic methods such as Raman scattering and IR absorption, as well as structural methods such as x-ray and n-diffraction, offer rather ambiguous interpretation of the high-frequency phonon spectrum of CsH₂PO₄ (CDP), especially regarding the proper assignment of proton vibrational modes. Empirical lattice dynamics (LD) simulations of the proton vibrational density of states ((H-VDOS)) in CDP also reveal a discrepancy in the frequency assignments of the OH stretching modes of its two non-equivalent hydrogen bonds. This may be resolved by accounting for the LD simulated directional (H-VDOS) along the three Cartesian axes of CDP, from which the corresponding anisotropy of the proton kinetic energy tensor can be deduced. The results may then be tested by a simple deep inelastic neutron scattering (DINS) measurement on a single crystal of para-electric CDP at room temperature.     

Preparation,characteristics and crystal structures of novel N-heterocyclic carbene substituted furan- and pyridine-containing azadithiolate Fe–S complexes

Two novel N-heterocyclic carbene disubstituted furan- and pyridine-containing azadithiolate Fe-only hydrogenase models (2 and 4) have been synthesized, and characterized by IR and ¹H NMR spectra and X-ray single crystal diffraction. Cyclic voltammetry (CV) experiments indicate that they show more negative reductive potentials at −2.53 V and −2.49 V, respectively versus the ferrocene/ferrocenium couple (Fc/Fc⁺) and are easier to capture proton attributing to the strong electron-donating ligand NHC. After the protonation under F₃CCO₂H the reductive potentials of 2 and 4 have 1.02 V and 0.77 V shifts, indicating the formation of Fe–H–Fe bond. The results also are confirmed by the data changes in IR spectra and the negative H signals are detected by ¹H NMR spectra at −27 ppm and −55 ppm.     

Stereochemistry of nitrogen heterocycles. 69. 13C NMR spectra of stereoisomeric 10-methyl-5-oxygen-substituted trans-decahydroquinolines

The ¹³C NMR spectra of 5-keto- and 5a- and 5e-hydroxy-10-methyl- and 1,10-dimethyltrans-decahydroquinolines have been recorded and interpreted. The increments of the oxo and hydroxy groups in the 10-methyldecahydroquinoline and the isostructural 10-methyldecaline systems were compared. The difference between the increments of azacyclic and the carbocyclic systems appears- at the -positions relative to the electronegative substituents (C₍₇₎ and C₍₉₎) and at the antiperiplanar -positions relative to nitrogen (C₍₅₎ and C₍₇₎). The increments of the oxo and the equatorial hydroxy groups in the aza ring are more shielded than in the carbon ring (at C₍₇₎, 2 ppm; at C_(g), 1 ppm), while the increments of the axial hydroxy group are more deshielded (at C₍₅₎, 1.5–2.0 ppm; at C₍₉₎, 1.0–1.5 ppm). The more the respective carbon atoms of the heterocycle are hydrogenated, the stronger are the deshielding -effect and the shielding -effect of the methyl group on nitrogen.For Communication 68, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 60–65, January, 1990.     

An external helium flushed milli-beam for combined PIXE and PIGE analysis

A helium flushed external beam PIXE/PIGE facility for nondestructive multielemental analysis has been developed and tested. By using proton energies E_p4.1 MeV and simultaneous detection of X- and gamma-rays, nearly complete analysis of all elements is achieved with nondestructively low ion current of I_p1 nA (except H, He, C, O and Ne are detected in a single measurement with sensitivities from the ppm level to about one percent). For most of the elements there are at least two channels of identification, which is a special advantage in analyzing unfavourable matrices, where the radiations of certain elements may interfere with each other.     

Substituent effects in 13C NMR spectroscopy: Methyl,ethyl, 2-propyl and 2-methyl-2-propyl carboxylates

The ¹³C chemical shifts of the 28 carboxylic esters have been determined by high-resolution NMR spectroscopy with the aid of proton decoupling. A linear relationship is shown to exist between the ¹³C chemical shifts of the carbinyl carbon (C-1) of the esters and the pK_a values of the acids from which they are derived. This is a consequent of the polar character of the

bond. Similarly, if the carboxyl group is kept constant, but the alcoholic part of the ester is varied from primary to secondary and tertiary alcohols, the esterification effect on C-1 can be correlated with the increasing stability of the +δ charge on the carbinyl carbon. The smallest esterification effect at C-1 (1.3 ppm, relative to the parent alcohol) is observed for methyl pivalate (pK_a 5.03 for the parent acid), and the highest effect (17.7 ppm) for 2-methyl-2-propyl trichloroacetate (pK_a 0.70). In contrast, the C-2 esterification effect has been found to be essentially constant (?3.8±0.7 ppm), which is in agreement only with a conformation of the ester group in which the carbinyl carbon is cis with respect to the CO group.     

A solid-state NMR study of cellulose degradation

A series of laboratory-aged transformer insulating papers were investigated using solid-state NMR spectroscopy. Carbon-13 CPMAS, and proton MAS experiments were carried out along with static proton relaxation (T₁, and T₁) and free induction decay (FID) measurements. Some proton CRAMPS and proton-carbon-13 correlation (WISE) experiments were also undertaken. A change in the proton T₁ and FID with ageing was detected. No detectable change was found in the proton T₁. Some amorphous cellulose was detected in the carbon-13 spectrum. There was, however, no evidence for a substantial change in the nature of the cellulose with ageing. The carbon-13 spectra from some aged samples showed signals not present in the spectrum from an unaged sample. This was taken to be evidence of chemical degradation. Proton MAS and the WISE exeriment gave some information about the nature of the water in the sample.     

Conformation of monobenzyl ethers of piperidyl-containing acetylenic glycols,according to13C NMR spectroscopic data

In the¹³C NMR spectra of individual ()- and ()-epimers (through the C₄ carbon atom of the six-membered ring) of monobenzyl ethers of piperidyl-containing acetylenic glycols, it has been found that the chemical shifts of the epimers differ by as much as 3 ppm for the C₂, C₄, and C₆ carbon atoms. The most probable conformations of the epimers are suggested, including intramolecular hydrogen bonds between the proton of the OH group and the unshared electron pair of the nitrogen.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2780–2785, December, 1991.     

Cationic Heteroconjugation Constants in the OHN+ and NHO+ Systems in Propylene Carbonate: Dependence on Difference in Basicity

Cationic heteroconjugation equilibria of more than ninety systems consisting of substituted pyridines, their N-oxides, and trimethylamine N-oxide, i. e., in systems with mixed hydrogen bridges of type OHN⁺ (NHO⁺) were studied in propylene carbonate. Both experimental systems without proton transfer, BH⁺/B₁, and those with proton transfer, B₁H⁺/B, were explored. The stability of the mixed hydrogen bridges, OHN⁺ (NHO⁺), is compared with that of the OHC⁺-type bridges. The influence of the difference in basicity of the conjugate base of the proton donor and the proton acceptor on the presence of the proton transfer equilibria, and, consequently, the possibility of determination of the cationic heteroconjugation constant values is discussed.     

Analysis of oxides, carbides and iron-rich particles in magnesium

Summary A new method for quantitative analysis of inclusions in magnesium has been developed. 5 g samples are dissolved in absolute methanol and the content of the undissolved particles is measured with X-ray fluorescence and their size distribution by Coulter Counter or Scanning Electron Microscope (SEM). Microprobe and SEM-analysis revealed that the undissolved particles are MgO, Al₄C₃, CaC₂, (Fe,Mn)₃Si, -(Fe,Mn) and -Fe. The samples analyzed contain 15–30ppm MgO, 2–4ppm Al₄C₃, <1ppm CaC₂ and 45–270 ppm iron-rich particles. The results have been compared and found in agreement with neutron activation analysis of oxygen, gas-chromatographic analysis of carbides and spectrographical measurements of iron in parallel magnesium samples. The new method has also been used for measurements of the magnesium content in dust.

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Analyse von Oxiden, Carbiden und eisenreichen Teilchen in Magnesium

Zusammenfassung Eine neue Methode wurde entwikkelt zur Analyse von Einschlüssen in Magnesium, ausgehend von 5 g-Proben, die in reinem Methanol aufgelöst werden. Der Gehalt der unlöslichen Teilchen wurde röntgenfluorescenzanalytisch und ihre Größenverteilung mit einem Coulter Counter oder Rasterelektronenmikroskop (REM) gemessen. Mikrosonden- und REM-Untersuchungen zeigten, daß die unlöslichen Teilchen aus MgO, Al₄C₃, CaC₂, (Fe,Mn)₃Si, -(Fe,Mn) und -Fe bestanden. Die untersuchten Proben enthielten 15–30 ppm MgO, 2–4ppm Al₄C₃, <1 ppm CaC₂ und 45–270 ppm eisenreiche Teilchen. Die Ergebnisse stimmten mit denen der neutronenaktivierungsanalytischen Sauerstoffbestimmung, der gaschromatographischen Carbidanalyse und spektrographischen Eisenbestimmung in Parallelproben überein. Das Verfahren wurde auch zur Bestimmung des Magnesiumgehaltes in Staub eingesetzt.

     

Pyrroles from ketoximes and acetylene

The reaction between ketoximes CH₃(RCH₂)C = NOH and acetylene in the presence of KOH and dimethyl sulfoxide at 120°C leads exclusively to 1-vinyl-2-methyl-3-R-pyrroles in 73–87% yields. The regiospecificity of the reaction is disrupted when the temperature is raised, and the fraction of a second isomer (1-vinyl-2-RCH₂-pyrrole) reaches 20–50% at 140°C. Regioselectivity is not observed for R¹CH₂(R²CH₂)C = NOH (R¹ and R² = n-alkyl). The relative shifts of the signals of the ring protons and the vinyl group for a number of 2-alkyl-1-vinyl- and 2,3-dialkyl-1-vinylpyrroles were measured. Alkyl substituents have a distinct effect on the chemical shifts of the protons of the 4–5 bonds. As the volume of the 2-alkyl substituent increases the protons of the N-vinyl group are deshielded by 0.10–0.13 ppm, and the 4-H ring proton is shielded by 0.05–0.16 ppm; this is explained by steric inhibition of the p- conjugation in the N-vinyl group during an s-trans(anti)-gauche conformational transition.This is actually communication XVI. The first publications (for example, see [1–3] and the literature cited in them) were not numbered.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 54–59, January, 1978.     

Asymmetric Synthesis of Phosphinous Tungsten Complexes

Abstract

The asymmetric synthesis of phosphinous compounds from diheterophosphacycloal kane-1,3,2 was investigated in a transition metal complex series. Complexes 1 and 2 were prepared from diaminophosphine, (?)-ephedrine and W (CO)₅ THP (1: δ³¹ P=+147,6 ppm; J_PW=313 Hz M^.+=595;2 δ³ p=+156 ppm J_PW=304 Hz M^.+=533; 90%dp) in two steps. Methyl lithium reacted with 1 to give stereospecific 3 (83%Yield) by P-O linkage (3 δ³¹ P=+64 ppm; J_PW =261 Hz; M^.+ ? 28=583). The aminophosphine complex 3 was stereochemically stable and was used for studies of synthetic applications. HCL gas reacted with 3 in CH₂Cl₂ to give the non optically active chlorophosphine complex 4 (δ³¹ P=+103,6 ppm; J_PW=290 Hz; M^.+ =482). This compound immediately gave salt 6 (δ³¹ P=+66,7 ppm; J_PW =240 Hz) by reaction with (?)-menthol and triethylamine. The acid methanolysis of 3 gave a mixture of 5 and 6 and the unchanged (?)-ephedrine salt [5:30% yield; δ³¹ P=+114 ppm; J_pw=280 Hz; [α]_D=+1,2° (CH₂Cl₂); M^.+=478; 6 : 60% yield; δ³¹p=+102,9 ppm; J_PW=264 Hz; [α]_D =+16,9° (CH₂Cl₂); M^.+=464]. Compound 6 was thus obtained with a 80% yield and a specific rotation of + 20,2° (CH₂Cl₂) in isopropanol/H₂SO₄ 5M medium. The enantiomeric excess of 6 was determined by RMN³¹P. Acid hydrolysis of 3 or the reaction with CH₃SO₃H, gave phosphinous acid complex 6 with an optical rotation of + 4,8° or ?1,8° respectively. These results provide precious informations about the stereochemistry and reactivity of the P-N linkage in this aminophosphine transition metal series, which differs notably from that of the corresponding (PO) N bond.     

Hydrogen Evolution at Liquid–Liquid Interfaces

Blowing bubbles : Hydrogen evolution by proton reduction with [(C₅Me₅)₂Fe] occurs at a soft interface between water and 1,2‐dichloroethane (DCE). The reaction proceeds by proton transfer assisted by [(C₅Me₅)₂Fe] across the water–DCE interface with subsequent proton reduction in DCE. The interface essentially acts as a proton pump, allowing hydrogen evolution by directly using the aqueous proton.

     

Synthesis,spectral studies,antimicrobial and insect antifeedant activities of some substituted styryl 4′-fluorophenyl ketones

Good yield of some substituted styryl 4′-fluorophenyl ketones were synthesized by solvent free fly-ash:water catalyzed eco-friendly environmentally benign Aldol reaction. These chalcones were characterized by physical constants, micro analysis and spectral data. Antimicrobial and insect antifeedant activities were measured in all chalcones. The group frequencies of all chalcones like carbonyl stretches νCO, C–F and the deformation modes of vinyl part of CH– out of plane, in-plane, CHCH out of plane and >CC< out of plane (cm⁻¹), the vinyl hydrogen and carbons δ(ppm) of H_α, H_β, C_α, C_β and CO were assigned and these frequencies were correlated with various kinds of substituent constants. From the results of statistical analysis the influence of electronic effects of substituents on the spectral data of carbonyl group, vinyl proton and carbons of the ketones have been explained.     

Bestimmung von Calciumgehalten im ppm-Bereich in Natriummetall mit Hilfe der R?ntgenfluorescenzanalyse

Zusammenfassung Eine Methode zur Bestimmung von Calcium in Natriummetall wird beschrieben. Das Natriummetall wird mit Methanol, H₂O und H₂SO₄ zu Na₂SO₄ umgesetzt, dieses in einem Platin-Tiegel zu Scheiben geschmolzen und diese direkt mit dem Röntgenfluorescenzgerät gemessen (Cr-Röhre, 55 kV, 36 mA; Analysatorkristall LiF; Ca-K-Linie, 113,01°). Die Nachweisgrenze dieser Methode liegt bei 4 ppm und gestattet daher noch eine sichere Aussage über die bei Na-Metall Reaktorqualität geforderte Spezifikation < 10 ppm Ca.

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Determination of ppm amounts of calcium in sodium metal by X-ray fluorescence analysis

The metal is converted to Na₂SO₄ by treatment with methanol, water and sulphuric acid. The salt is fused in a platinium crucible to form disks which can be directly measured in the X-Ray fluorescence apparatus (Cr tube, 55 kV, 36 mA; analyzing crystal LiF; Ca-K-line, 113.01°). The limit of detection of the method is as low as 4 ppm and thus permits reliable statements with regard to the specification < 10 ppm Ca required for reactor quality sodium metal.

     

Gas-Phase Reactions of Dimethyl Disulfide with Aliphatic Carbanions - A Mass Spectrometry and Computational Study

Ion-molecule reactions of Me₂S₂ with a wide range of aliphatic carbanions differing by structure and proton affinity values have been studied in the gas phase using mass spectrometry techniques and DFT calculations. The analysis of the spectra shows a variety of product ions formed via different reaction mechanisms, depending on the structure and proton affinity of the carbanion. Product ions of thiophilic reaction (m/z 47), S_N2 (m/z 79), and E2 elimination – addition sequence of reactions (m/z 93) can be observed. Primary products of thiophilic reaction can undergo subsequent S_N2 and proton transfer reactions. Gibbs free energy profiles calculated for experimentally observed reactions using PBE0/6-311+G(2d,p) method show good agreement with experimental results.

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Graphical Abstract ?

     

Analytical block-diagonalization of matrices using unit spherical tensors

A new method for block-diagonalizing large Hamiltonian matrices, in closed form, is described. The method is based on (i) a general unitary transformation due to Slichter, and (ii) Fano's unit spherical operatorsÛ _Q ^K (I _i,I _i). The method is illustrated with a simple three spin 1/2 dipolar coupled spin system, characterized by off-block-diagonal unit spherical tensorsÛ ₀ ² (3/2,1/2,) andÛ ₀ ² (3/2,1 /2,). In addition, it is pointed out that any Hamiltonian matrix can be re-labelled in terms of fictitious spin labels, enabling a wide variety of unit spherical tensors to be used in block-diagonalization. For example, a single spin 5/2 matrix can be re-labelled using three spin labels 1/2, 1/2, and 1/2, respectively. Thus the tensor algebra required to block-diagonalize a 6 x 6 matrix is determined solely by the properties of the Pauli spin matrices. Finally, it is shown that re-labelling within the unit spherical tensor framework provides a unifying framework for standard basis operators, fictitious spin 1/2 and 1 operators, and others. The fictitious spin 1 / 2 unit spherical operators discussed in this paper differ from those of Vega and Pines.     

Theoretical study on sulfonated and phosphonated poly[(aryloxy)phosphazenes] as proton-conducting membranes for fuel cell applications

Polyphosphazenes are considered to be more useful as proton-conducting membranes than Nafion due to their low methanol permeability, low water swelling ratios, satisfactory mechanical properties, and conductivities comparable to those of Nafion. In this work, compounds 1-6, six polyphosphazenes with different side groups, were designed and calculated. Structural parameters, proton affinities and water adsorptions were obtained on the basis of the optimized geometrical structures. Our calculations were in agreement with experimental results. It was found that the proton conductivities of the sulfonated poly[(aryloxy)phosphazenes] (R¹SO₃H) are higher than those of the phosphonated ones (R¹PO₃H₂), while the phosphonated poly[(aryloxy)phosphazenes] will retain water better at higher temperature than the sulfonated ones. The electron-withdrawing substituent of R² is beneficial to proton conductivities and water adsorptions of both sulfonated and phosphonated poly[(aryloxy)phosphazenes].     

Exciton Chirality Method. Oriented Molecules – Anisotropic Phases

Summary. The results of the theory of the anisotropy of optical activity (ACD), especially of the circular dichroism (CD), in view of its application to the exciton chirality method was presented. In order to introduce the phenomenology some typical experimental anisotropy effects of the ACD of a dibenzoate and two taddoles were discussed. The CD and ACD of unbridged and bridged 1,1-binaphthols were described taking into account results of the polarized spectroscopy. Their CD and ACD spectra were decomposed into contributions of their two exciton transitions. It was proven that the electric dipole/electric quadrupole transition moments contribute in same order of magnitude as the electric dipole/magnetic dipole transition moments to the tensor coordinates of the CD tensor for a bridged 1,1-binaphthol. The CD tensor coordinates _ii^* for a light beam propagation along the principal axes of the order tensor of a 1,1-binaphthol of approximately C₂ symmetry are very different in size and also of different sign. The largest tensor coordinate belongs to the direction along the naphthyl–naphthyl bond. The CD along the C₂ symmetry axis is approximately zero. The CD tensor coordinates of different sign along different directions within a molecule can be assigned to different helicities in their molecular structure along these directions. For (R)-1,1-binaphthol skeleton the left handed helix along an axis, which is perpendicular to the naphthyl–naphthyl bond and perpendicular to the C₂ symmetry axis, leads to a positive couplet whereas for the right-handed helix along the naphthyl–naphthyl bond a negative couplet has been found. Thus, the ACD with its determination of the _ii^* allows to observe different helicities along different directions within a molecule. As well for the bridged as the unbridged binaphthols in the spectral region of the exciton bands a third transition not belonging to the exciton band system was detected.     

Exciton Chirality Method. Oriented Molecules – Anisotropic Phases

The results of the theory of the anisotropy of optical activity (ACD), especially of the circular dichroism (CD), in view of its application to the exciton chirality method was presented. In order to introduce the phenomenology some typical experimental anisotropy effects of the ACD of a dibenzoate and two taddoles were discussed. The CD and ACD of unbridged and bridged 1,1-binaphthols were described taking into account results of the polarized spectroscopy. Their CD and ACD spectra were decomposed into contributions of their two exciton transitions. It was proven that the electric dipole/electric quadrupole transition moments contribute in same order of magnitude as the electric dipole/magnetic dipole transition moments to the tensor coordinates of the CD tensor for a bridged 1,1-binaphthol. The CD tensor coordinates _ii^* for a light beam propagation along the principal axes of the order tensor of a 1,1-binaphthol of approximately C₂ symmetry are very different in size and also of different sign. The largest tensor coordinate belongs to the direction along the naphthyl–naphthyl bond. The CD along the C₂ symmetry axis is approximately zero. The CD tensor coordinates of different sign along different directions within a molecule can be assigned to different helicities in their molecular structure along these directions. For (R)-1,1-binaphthol skeleton the left handed helix along an axis, which is perpendicular to the naphthyl–naphthyl bond and perpendicular to the C₂ symmetry axis, leads to a positive couplet whereas for the right-handed helix along the naphthyl–naphthyl bond a negative couplet has been found. Thus, the ACD with its determination of the _ii^* allows to observe different helicities along different directions within a molecule. As well for the bridged as the unbridged binaphthols in the spectral region of the exciton bands a third transition not belonging to the exciton band system was detected.     

Structural and spectral studies of 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one and its diorganotin(IV) complexes

Two diorganotin(IV) complexes of the general formula R₂Sn[Ph(O)CCH-C(Me)N-C₆H₄(O)] (R = Ph, 1a; R = Me, 1b) have been synthesized from the corresponding diorganotin(IV) dichlorides and the ligand, 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one (1) in methanol at room temperature in presence of triethylamine. Both compounds have been characterized by elemental analyses, IR and ¹H, ¹³C, ¹⁵N, ¹¹⁹Sn NMR spectra. The structures of the free ligand and the complexes have been confirmed by single crystal X-ray diffraction. There are three independent molecules in the crystal structure of the ligand 1 and in all three the O-bound proton is transferred to the imine nitrogen and makes an intramolecular N-H?O hydrogen bond with the carbonyl oxygen. In turn this makes an intermolecular hydrogen bond with the phenolic H atom. The crystal structure of 1 is trigonal and a new polymorph; triclinic and monoclinic forms have already been published. In 1a, the central tin atom adopts distorted trigonal-bipyramidal coordination geometry whereas in dimeric 1b it is distorted octahedral when including the intermolecular Sn-O(phenolic) bond [2.7998(20) Å]. The δ (¹¹⁹Sn) values for the complexes 1a and 1b are −306.6 and −127.9 ppm, respectively, thus indicating penta-coordinated Sn centres in solution.