23Na NMR study of ionic mesophases in molten sodium carboxylates

The ²³Na NMR lineshapes are reported for the ionic mesophase and isotropic phase of the melts of sodium n-butyrate and sodium isovalerate. The powder pattern for the central transition typical for the second-order quadrupole effect observed in the mesophase melts is of particular interest. Some analogies to ²³Na behavior in sodium β-alumina are pointed out.     

NMR study of 23Na complexing by polyethers,siloxanes and polyamides

Complexation of Na⁺-ion with polyethers and polyamides is studied by using ²³Na NMR spectroscopy. The variation of the linewidth and the position of the ²³Na NMR signal give evidence for the interaction of oxygen atoms of poly(ethylene oxide) in acetonitrile and those of siloxanes in T.H.F. with the solvated ion. In addition chemical shift data are given for perturbation of the Na⁺ solvation shell by interaction of the ion with substituted amides and polyamides in T.H.F.     

用23Na和27Al固体核磁共振研究Na+在γ-Al2O3上的吸附状态

The adsorption of Na~+ on γ-alumina surface at four coverages of Na_2CO_3 (5%, 10%, 15%, and 20% wt/wt) was characterized by solid-state ~(23)Na and ~(27)Al NMR spectroscopy. The experimental results suggest that two distinct adsorbed species are present on alumina surface: surface species and surface salts. At lower coverages of Na_2CO_3 (5% and 10%), a surface species is predominant, in which the Na~+ cations are associated with the oxygen atoms of γ-alumina. With increasing the loading level to 15%, a second adsorbed species begins to appear which is attributed to the surface salt, Na_2CO_3, deposited on the solid surface. Further adsorption of Na_2CO_3 leads to an increase in the amount of surface salt while the amount of surface species remains unchanged. ~1H-~(27)Al CP/MAS experiments give the evidence that some Na~+ cations in the form of surface species are coordinated with the Br~(‥)onsted acid sites of γ-alumina. This may be the main driving force that improves appreciably the catalytic efficiency of Na_2CO_3/γ-Al_2O_3 catalyst.     

Na4Sn9与一些配合物相互作用的119Sn和23Na NMR研究

以¹⁹⁹Sn和²³Na核磁共振研究了Na₄Sn₉-乙二胺体系中加入M(acacen)(M=Cu²⁺,Ni²⁺)和Ln(fod)₃(Ln=Pr³⁺,Yb³⁺,Eu³⁺)后的化学位移和偶合常数。结果表明,假接触和体积磁化率的变化是引起化学位移变化的主要原因,而Fermi接触的贡献可以忽略。     

Nuclear magnetic relaxation of 23Na in polyelectrolytes with mono/divalent ion clouds

The nuclear magnetic relaxation rate of ²³Na ions in polyelectrolyte solutions containing both monovalent and divalent counter-ions is investigated to obtain information on the nature of the divalent ion/poly-ion interaction.     

Ab initio calculation of the equilibrium geometry and the 13C, 17O, 23Na and 7Li NMR shielding tensors of the systems Na+/CO and Li+/CO

Using ab initio SCF calculations two minima have been found in Na⁺/CO and Li⁺/CO. The minimum corresponding to CO…Na⁺ is slightly deeper than in Na⁺…CO. The minimum corresponding to CO…Li⁺ is deeper than in Li⁺…CO. The ¹³C, ¹⁷O, ²³Na and ⁷Li NMR shielding tensors were computed with the coupled Hartree—Fock method with large gaussian basis sets.     

Long-range electric field gradients in charged polymer solutions as probed by 23Na relaxation

Bi-exponential ²³Na nuclear magnetic relaxation is shown to be a general phenomenon in aqueous solutions of charged polymers in the semi-dilute region. Dependence on concentration, degree of polymerization, degree of ionization and presence of simple salt is established and discussed.     

On the concentration dependence of the nature of polyelectrolyte solutions as detected by 23Na relaxation

Dependence of ²³Na nuclear magnetic relaxation on concentration and degree of polymerization is reported for solutions of Na polystyrenesulfonate. In the concentration range 10^?1 ? c 10^?1 eq/e, ²³Na relaxation is far outside the extreme-narrowing limit and relaxation rates depend on the degree of polymerization. These phenomena seem to disappear outside this range.     

Neutron activation analysis of aluminium with radiochemical separation of 24Na

Summary In the irradiation of aluminium with fission neutrons, dominant radioactivity of ²⁴Na (t _1/2=15.03 h) is produced from the matrix element by fast neutrons via the ²⁷Al(n,) reaction. The high Compton underground resulting from this matrix radionuclide is a serious limiting factor of the determination of low contents of elemental impurities in aluminium by direct gamma ray spectrometry via indicator radionuclides with t _1/23 d. A specific removal of this matrix activity was achieved by adsorption of sodium (> 99%) on hydrated antimony pentoxide from a HCl/HF-medium, while 48 other elements remain in the eluate with yields > 99% and the elements Br, Cs, K, Rb, and Se with yields between 93–98.5%. Applying this radiochemical separation to the analysis of high purity aluminium, the limits of detection could be improved by a factor up to 200. The attainable limits of detection are at the 0.01 ng/g level for Au, Eu and Sc, at the 0.1 ng/g level for

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Neutronenaktivierungsanalyse von Aluminium mit radiochemischer Abtrennung von ²⁴Na

Zusammenfassung Bei der Bestrahlung von Aluminium mit Spaltneutronen wird durch die ²⁷Al(n,)-Reaktion aus dem Matrixelement eine dominierende Aktivität von ²⁴Na (t _1/2=15,03 h) gebildet. Der aus dieser Matrixaktivität resultierende hohe Comptonuntergrund stellt eine wesentliche Beeinträchtigung der direkten gammaspektrometrischen Bestimmung von sehr kleinen Spurenelementgehalten in Aluminium über Indicatorradionuklide mit t _1/23d dar. Eine spezifische Abtrennung dieser Matrixaktivität wurde durch Adsorption des Natriums (< 99%) an hydratisiertem Antimonpentoxid aus HCl/HF-Medium erreicht, während 48 andere Elemente mit Ausbeuten > 99% und die Elemente Br, Cs, K, Rb und Se mit Ausbeuten zwischen 93–98,5% im Eluat verbleiben. Bei Anwendung dieser radiochemischen Trennung für die Analyse von hochreinem Aluminium können die Nachweisgrenzen der INAA um einen Faktor bis 200 verbessert werden. Die erreichbaren Nachweisgrenzen liegen in der Größenordnung von 0,01 ng/g für die Elemente Au, Eu und Sc, von 0,1 ng/g für Co, Cs, Dy, Hf, Ir Lu, Mn, Re, Sb, Sm, Ta, Tb, Th, U und Yb, von 1 ng/g für Ag, As, Cd, Ce, Cr, Cu, Er, Ga, Hg, Ho, In, La, Mo, Pt, Rb, Ru, Se, Te, Tm und W und zwischen 10 ng/g und 7 g/g für die Elemente Ba, Ca, Fe, Gd, K, Nd, Ni, Os, Pd, Pr, Sn, Zn und Zr.

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Dedicated to Prof. Dr. K. H. Lieser on the occasion of his 65th birthday     

17O-enriched α-azohydroperoxides: 17O NMR spectroscopy, 17O-labeling reagents

¹⁷O-enriched α-azohydroperoxides, prepared by autoxidation, are efficient ¹⁷O-labeling reagents; ¹⁷O NMR (CD₃CN) of 2 showed broad signals at δ 254 and 204 PPM; the solvent dependence of the ¹⁷O chemical shifts and the kinetics of ionic oxidations are interrelated.     

29Si and 13C NMR spectra of permethylpolysilanes

²⁹Si, ¹³C and ¹H NMR spectra are reported for the series of linear permethylpolysilanes Me(SiMe₂)_nMe where n = 1 to 6, for the cyclic permethylpolysilanes (Me₂Si)_n where n = 5 to 8, and for a few related compounds. For linear polysilanes the ²⁹Si and ¹³C chemical shifts can be accurately calculated from simple additivity relationships based on the number of silicon atoms in α, β, γ and δ positions. Adjacent (α) silicon atoms lead to upfield shifts in the ²⁹Si and ¹³C resonances, whereas more remote silicon atoms lead to downfield shifts. The ²⁹Si chemical shifts of the polysilane chains are linearly related to the ¹³C shifts of the carbon atoms attached to the silicon. The ²⁹Si and ¹³C resonances of the cyclic silanes deviate from this relationship. Ring current effects arising from σ delocalization are suggested as an explanation for the deviations. Proton-coupled ²⁹Si NMR spectra are reported for Me₃SiSiMe₃ and for (Me₂Si)_n, n = 5 to 7.     

13C NMR of pterocarpans

¹³CNMR spectra of eight pterocarpans are reported Assignments are based on multiplicities and second-order features in off-resonance decoupled spectra and on chemical shifts in model compounds. Comparison of the degree of long-range (C, H) coupling in ¹H-coupled spectra is found useful     

15N and 31P NMR spectroscopy of triclorophosphazopolyfluoroaryls.

¹⁵N and ³¹P NMR spectra of trichlorophosphazopolyfluoroaryls obtained by the interaction between polyfluoroanilines and PCI₅ in benzene (Kirsanov reaction) have been investigated. The interconversions of monomeric and dimeric forms of trichlorophosphazopolyfluoroaryls by ³¹P NMR are also shown.     

129Xe NMR: Porous-structure of silica gels

¹²⁹Xe NMR has been used to study the pore structure of several commercial silicas. They have been shown to possess micropores of 5–10 Å size. Micropores of different type appear not to be connected directly. A model is suggested explaining the experimental dependences of chemical shifts on temperature and pressure.     

1H,2H,19F and 31P NMR and ESR investigations of aryl-t-butyl nitroxides

Aspects of translocation of spin to fluorine and phosphorus are discussed. (2p–3d)_π overlap in phosphorus is insignificant. Spin polarization and (2p–3p)_π overlap are opposing spin transfer mechanisms for phosphorus. The³¹P NMR spectrum of the nitroxide from 7a shows some features which are not fully understood. Some gain in resolution of the NMR spectra can be achieved by deuteration, but it is considerably lower than predicted.     

14N and 13C NMR of tautomeric systems of hydroxy-pyridines

¹⁴N NMR is shown to be an efficient method of investigation of the tautomeric equilibria in hydroxy-and related substituted pyridines. Large relative ¹⁴N chemical shifts within tautomeric pairs estimated from N-Me and O-Me derivatives make possible quantitative determinations of the equilibria. Qualitative conclusions may be drawn from ¹⁴N line widths as well as from ¹³C and proton chemical shifts.     

NMR (1H, 13C, 29Si) study of some allylhalogenosilanes

¹H, ¹³C and ²⁹Si NMR spectra of the allylchlorosilanes (CH₂CH-CH₂-)_xSiCl_4?x and of triallylbromosilane have been analysed. Results are discussed in terms of inductive and steric effects and of contributions of diamagnetic anisotropy. There is no conclusive evidence for (p-d)π conjugation.     

13C-{1H} NMR spectra of episulphide copolymers

Ethylene sulphide-isobutylene sulphide and propylene sulphide-isobutylene sulphide copolymers have been prepared using anionic catalysts and investigated by ¹³C-{¹H} NMR spectroscopy. The carbon-13 NMR spectra are assigned in terms of diad and triad sequences. There is discussion of the effects of mono- or dimethyl substitution in the α, β, γ or δ positions on the chemical shift of the main chain carbon atoms. It has also been shown that for isobutylene sulphide, as for propylene sulphide, under the influence of an anionic catalyst, there is a normal ring opening only at the primary carbon atom.     

13C NMR spectrum of coumarin

Summary The positions of the signals from the C₃, C₅, C₆, and C₇ carbon atoms in the¹³C NMR spectrum of coumarin have been established with the aid of information obtained from the¹³C NMR spectra of [3-D]-, [4-D]-, and 7-methoxycoumarins and by the use of an additive calculation based on the increments of the methoxy group in the¹³C NMR spectrum of anisole.M. V. Lomonosov Moscow State University Scientific-Research Institute of Pharmacology, Academy of Medical Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 458–462, July–August, 1975.