Mössbauer Spectroscopic Studies of the Hydroxofluorostannate(IV) Complexes

Mössbauer isomer shifts of ¹¹⁹Sn in a series of complexes K₂Sn(OH)_6-mF_m observed at 78 K were ?0.05, ?0.05, ?0.24, ?0.27 and ?0.40 mm s^?1, respectively, for m=0, 2, 4, 5 and 6. These IS values were linearly related to both m and (the average Pauling electronegativity of the ligands): . The IS straight line was compatible within experimental error with the one reported by Parish and Row-botham for the hexahalogenostannate complexes SnX₄Y₂², namely, The revised IS straight line including both series of complexes could be expressed by the equation Quadrupole splittings observed in the complexes of m = 2,4 and 5 were 1.16, 0.80 and 0.73 mm s^?1 respectively. They were linearly related to both m and .     

Synthesis of Heterobimetallic Phosphido-Bridged W-Mo Complexes with Chelating dppe and dppm Ligands

Reactions between and bidentate phosphines (dppm and dppe) produced complexes and with chelating dppm and dppe ligands as only products. No bridging bidentate phosphine complex was observed. Both complexes were spectroscopically characterized.     

Structural studies on polyformals. III. Poly-1,3-dioxocane and poly-1,3-dioxonane

Molecular and crystal structures of poly-1,3-dioxocane and poly-1,3-dioxonane, the polyformals [? OCH₂O? (CH₂)_m? ]_m with m = 5 and m = 6, respectively, are analyzed. Poly-l13-dioxocane is triclinic, space group with m = 5 and m = 6, respectively, are analyzed. Poly-1,3-dioxocane is triclinic, space group (fiber axis) and N (number of chains per unit cell) = 2. Poly-1,3-dioxonane is orthorhombic, (fiber axis) = 18.8 Å, and N = 2. The molecular conformations are roughly where T, G, and G are the trans, and the two gauche forms, respectively.     

Anodic Deposition of Iodide Ion at Silver Electrode

Anodic deposition of iodide ion on silver at 25° in aqueous (0.5 M KNO₃) and in 90% (w/w) ethanol-water (0.05 M KClO₄) solutions was studied galvanostatically. The exchange current density, transfer coefficient and the rate constants for the electrode reaction were evaluated. The experimental results revealed that the overall electrode reaction and the charge-transfer step was the same one, i.e., , which might be assumed highly reversible as reflected by the exchange current density (i) and transfer coefficient (α). The numerical values of the rate constants, and at 25° were, in aqueous solution, 1.02×10^?5 and 2.88×10^?6, and in ethanol solution, 2.88×10^?5 and 6.3×10^?6 cm sec^?1, respectively.     

13C NMR spectra of 2,3-dihydro-1H-pyrrolo[1,2-c]imidazol-1,3-dione and its thione analogues

Analysis of the ¹³C NMR spectra of a series of 2,3-dihydro-1H-pyrrolo[1,2-c]imidazole derivatives has provided chemical shift data for (?184 ppm), (?173.5 ppm), (?158 ppm) and (?148 ppm) groups. A full analysis of the ¹³C chemical shifts of the C atoms of the pyrrole ring and of an N-phenyl substituent is described.     

Effects of linking groups in fluorinated aromatic polyamides

Based on dynamic thermogravimetric analysis (TGA) of fluorinated aromatic polyamides, we found that substituting terephthaloyl units for isophthaloyl units usually increased the thermal stability of the polymers. In contrast, the first steps of thermal degradation of poly(5,5′-sulfonyl-2,2′-difluoro-diphenyl terephthalamide) (2,2′-DIF-PSDPT) and poly(5,5′-sulfonyl-2,2′-difluorodphenyl isophthalamide)(2,2′-DIF-PSDPI) followed almost the same curve. This was attributed to the relative flexibility of the ? SO₂? group, and also to the activating effect on the dehydrofluorination reaction, which was believed to be the first step of the degradation of the ortho-fluorinated aromatic polyamides, , resulting in the formation of benzoxazole groups, , on the polymer backbone. With fluorinated aromatic polyamides having ortho fluorine to the amide nitrogen, the electron releasing ? CH₂? group deactivated the nucleophilic substitution of the dehydrofluorination reaction and the electron withdrawing group ? SO₂? activated the reaction, so that the onset degradation temperatures of the fluorinated aromatic units R in followed the order:      

Representable reference density matrices induced by information theory

A class of reference full density matrices and their reduced density matrices is presented. These density matrices are designed to be of value as references from which to describe and measure the effects of electron correlation in atoms, molecules, and solids. A given reference full density matrix is constructed to contain the least possible information consistent with having the (recognized) symmetry properties of—and reducing to the 1-matrix of—a given “true” full density matrix (which in a typical application is constructed from a correlated variational wave function). Therefore, the reduced density matrices derived from are representable and depend only upon the 1-matrix of and the (recognized) symmetry properties of for their construction. Furthermore, the property of containing the least possible information consistent with the given constraints makes these reference density matrices ideally suitable as references from which to describe the electron correlation contained in the “true” full density matrix .     

Studies on polyyne polymers containing transition metals in the main chain. IV. Polymer synthesis by oxidative coupling of transition metal-bis(acetylide) complexes

The metal-polyyne polymers consisting of transition metals and conjugated tetrayne systems where M represents ? Pt(PBu₃)₂? or ? Pd(PBu₃)₂? moiety were prepared by the oxidative coupling method and characterized by spectral analysis, associated with novel depolymerization giving binuclear transition metal complexes, and      

Structure and formation of some [C4H5O2]+ ions generated by radical losses in pseudo simple cleavage reactions

Characterization of some [C₄H₅O₂]⁺ ions in the gas phase using their collisional activation mass spectra shows that the isomeric ions \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_3 {\rm OCH = CH} - \mathop {\rm C}\limits^ + {\rm = O,} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm HC} \equiv {\rm C} - \mathop {{\rm C}({\rm OH}){\rm OCH}_3 }\limits^ + $\end{document} are stable for t?10^?5 s. Of these, ions of structure were generated by the site specific gas phase protonation of γ-crotonolactone with isobutane or methanol as chemical ionization reagent gases. These results and those derived from measurements on some ²H, ¹³C and ¹⁸O labelled [C₄H₅O₂]⁺ product ions, were used to study the mechanisms of unimolecular radical elimination reactions, viz. (1) loss of CH₃˙ from [trans-methyl crotonate], (2) loss of H˙ from [methyl acrylate]⁺˙, (3) loss of H˙ from [cyclopropane carboxylic acid]⁺˙ and (4) loss of CH₃˙ from [1,3-dimethoxypropyne]⁺˙. It is concluded that none of these losses occur by simple bond cleavage. Mechanisms are presented which account for the observation that the first three reactions yield product ions of structure whereas the ions generated by reaction (4) have structure \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_3 {\rm OCH = CH} - \mathop {\rm C}\limits^ + {\rm = O}{\rm .} $\end{document}. It is further proposed that a minor fraction of the [M-CH₃]⁺ ions from ionized trans-methyl crotonate is generated via a rearrangement process which yields ions of structure \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_3 {\rm OCH = CH} - \mathop {\rm C}\limits^ + {\rm = O}{\rm .} $\end{document}.     

Field Sweep Spin Decoupling of Weakly Coupled Unsymmetrical Three-Spin System

Proton magnetic resonance spectrum of 25% (volume) methyl 2,3-dibromopropionate in benzene exhibits a typical ABC pattern in which the four strong lines from each nucleus can be immediately recognized. The assignment of spectral lines and the determination of energy-level diagram were thus straightforward. Field-sweep spin decoupling experiment with respect to the outer transition-square of the sample was found to be in complete analogy with two-spin AX system. However, spin decoupling with respect to the inner transition-square reveals a weak satellite line on each side of the decoupled A (or C) signal. These weak satellite lines are found to be due to J_AB (or J_BC) and may prove to be useful for the direct determination of J_AB and J_BC.     

Concentration fluctuation effects for dynamics of polymer solutions

Dynamics of concentration fluctuation in a semidilute polymer theta-solution in the regime of entanglements is studied theoretically. A number of relaxation modes is predicted, the largest amplitude corresponding to a reptation mode with the time , where q is the wave vector, the static correlation length, R the size of a polymer coil. A mode with a “superlong” time N²q⁻² is predicted for . It is shown also that fluctuations of molecular field result in a substantial decrease of macromolecular curvilinear diffusion constant. The same effect gives rise to an increase of zero-shear viscosity of the solution; the dependence of viscosity on number of links per chain, N, is much stronger than N³ in the regime of high N.     

An NMR study of cis-2-butene partially oriented in a nematic phase

The NMR spectrum of cis-2-butene partially oriented in a nematic phase has been analysed, and information about the geometry and the indirect spin-spin coupling constants has been obtained. Assuming the barrier of rotation of the methyl groups and other geometrical information from microwave studies, we obtained = 126 ± 2° and = 116.8 ± 0·6°. The angle that the CH₃ rotation axis makes with the double bond was calculated to be 127·5 ± 0.4°; this value is closely linked with the assumed value of = 109°28′.     

Anionic copolymerization of styrene and 1,1-diphenylethylene

Kinetics of anionic copolymerization of styrene (S) and 1,1-diphenylethylene (D) were investigated in THF. The rate constant of addition of D to living polystyrene was found to be k_{1,2 ±} = 250 l./mole-sec. for , Na⁺ ion-pair, and that for the free , Na⁺ ion is k_1,2?～400,000 l./mole-sec. Both values refer to 25°C. The addition of styrene to ? D^?, Na⁺ was found to be reversible: and k_2,1 was determined by three different methods to be ～0.5–0.7 l./mole-sec. Studies performed in a stirred-flow reactor led to k-₂₁ = 13 sec. ^?1 and K₂₁ ～ 5 × 10^?2 l./mole. An alternating copolymer is obtained in the presence of a large excess of 1,1-diphenylethylene.     

Electron impact studies. CI—negative ion mass spectra of the carbonyl group. The Aryl?CH2?CO- and Aryl?(CH2)2?CO- systems

Fragmentations of the molecular anions of m- and p-nitrophenyl-CH₂? CO? R yield nitrobenzyl anions in the ion source when R = Ph, but the corresponding ion from the system where R = Me is only formed after collision activation. o- and p-Nitrophenyl parent anions undergo β-cleavage to the carbonyl centre to produce nitrobenzyl anions. Pronounced rearrangement peaks are noted in the spectra of o-nitrophenyl- compounds. Labelling studies indicate the identity of the eliminated species, but the mechanisms of the rearrangements are complex.     

Pyrolysis of 2,4-dimethylhexene-l and the stability of isobutenyl radicals

2,4-Dimethylhexene-l has been decomposed in single-pulse shock tube experiments. Rate expressions for the initial reactions are and sec^?1 at 1.5–5 atm and 1050°K. This leads to ΔH^°_f300 (CH₂ = C(CH₃)CH₂) = 124 kJ/mol, or an allylic resonance energy of 50 kJ/mol. Rate expressions for the decomposition of the appropriate olefins which yield isobutenyl radicals and methyl, ethyl, isopropyl, n-propyl, t-butyl, and t-amyl radicals, respectively, are presented. The rate expression for the decomposition of isobutenyl radical is (at the beginning of the fall-off region). For the combination of isobutenyl and methyl radicals, the rate constant at 1020°K is Combination of this number and the calculated rate expression for 2-methylbutene-1 decomposition gives S. (1100) = 470 J/mol °K. This yields It is demonstrated that an upper limit for the rate of hydrogen abstraction by isobutenyl from toluene is      

Darstellung und Eigenschaften einiger Monoarylthalliumbis-dithiocarbamate und -xanthogenate

Synthesis and Properties of Some Monoarylthalliumbisdithiocarbamates and -xanthates The synthesis and properties of some compounds of the general formula R? T and are described. Crystalline substances were obtained, which can be characterized excellently by NMR spectroscopy. Reactions and NMR data are discussed.     

Cluster ions in the secondary ion mass spectrometry of choline and acetylcholine halides

Liquid secondary ion mass spectra of choline and acetylcholine halides exhibit several series of cluster ions whose origins were investigated using B/E and B²/E linked-scan techniques. In the case of choline halides three series of cluster ions were identified as (Me₃$ \mathop {\rm N}\limits^ + $CH₂CH₂OH + nM), (Me₃$ \mathop {\rm N}\limits^ + $CH₂CH₂OMe + nM) and (Me₃N$ \mathop {\rm N}\limits^ + $CH₂CH₂OH · Me₃$ \mathop {\rm N}\limits^ + $CH₂CH₂O^? + nM), while (CH₃COOCH₂CH₂$ \mathop {\rm N}\limits^ + $Me₃ + nM), (Me₃$ \mathop {\rm N}\limits^ + $CH₂CH₂OH + nM) and (CH₂ = CH$ \mathop {\rm N}\limits^ + $Me₃ + nM) were observed in the spectra of acetylcholine halides. For these cluster ions, bimolecular reactions induced on ion bombardment under secondary ion mass spectrometric conditions are discussed.     

The first normal stress difference and viscosity in shear of liquid crystalline solutions of hydroxypropylcellulose: new experimental data and theory

The constitutive equations for liquid crystalline polymers recently proposed by one of us [1] are applied here to interpret the behaviour of the shear viscosity η and the first normal stress difference N₁() measured for liquid crystalline (LC) solutions of hydroxypropylcellulose in acetic acid. N₁( ) is observed to change from positive to negative and again to positive, as the shear rate increases, at lower concentrations, in the LC phase. The -values at which N₁ changes sign depend on the molecular mass (degree of polymerization) and on the concentration. η shows a small Newtonian plateau at low shear rates and a strong shear-thinning at higher values of . The rate of decrease of η in this region shows an “hesitation” similar to one previously observed in LC solutions of poly-γ-benzyl-L-glutamate PBLG. All these observations can be rationalized within the frame-work of Martins' theory. The expressions for N₁() and η derived from this theory fit very well (quantitatively) to the experimental data and some fundamental viscoelastic parameters of the system under study are thereby obtained for the first time.     

Mössbauer Spectroscopic Studies of K2SnCl6 and SnCl4·5H2O in Frozen Aqueous Solutions and in Ion Exchange Resins

Concentration dependence of isomer shift of K₂SnCl₆ and tin(IV) chloride was studied. Tin was hydrolyzed in both cation and anion exchange resins after water washing. Two pairs of these two solutions showing the same isomer shift values, and therefore the same , were selected for further studies in HCl solutions and in anion exchange resins. The first pair was 0.04 M K₂SnCl₆ and tin(IV) chloride solutions (δ=0.00 mm/s; =0): Their δ-[HCl] curves coincided each other. Tin was sorbed on anion exchange resin as pentachlorstannate(IV) at (HCl)≤6 N, and chiefly as hexachlorostannate(IV) at [HCl]≥7 N. The both complexes were sorbed when 6 N < [HCl] < 9 N. The δ-[HCl] curves of the second pair, 0.4 M K₂SnCl₆ and 3 M tin(IV) chloride(δ =0.23 mm/s; =3), also coincided each other, and tin was sorbed as pentachlorostannate(IV) from K₂SnCl₆ solutions in the HCl concentration range studied (≥5 N).     

The Radicals and Radical Dianions of Bridged [11]- and [15]Annulenyls as Compared with Those of Benzotropyl and 2,3-Naphthotropyl

The 1,6-methano[11]annulenyl ( 1 ·), 1,6:8, 14-propane-1,3-diylidene[15]annulenyl ( 2 ·), benzotropyl ( 3 ·) and 2,3-naphthotropyl ( 4 ·) radicals have been characterized by their ESR. spectra. The corresponding radical dianions, , , and , have also been studied both by ESR. and ENDOR. spectroscopy. Assignment of the coupling constants a_Hμ to protons in the individual positions μ of these radicals and radical dianions is to a large extent based on investigations of specifically deuteriated derivatives. The radicals 1· , 2· , 3· and 4· exist in temperature-dependent equilibria with ( 1 )₂, ( 2 )₂, ( 3 )₂ and ( 4 )₂, respectively, where ( 1 )₂ to ( 4 )₂ denote mixtures of dimers of 1 · to 4 ·. The dissociation enthalpies, ΔH°, of ( 1 )₂ (102 kJ/mol) and ( 2 )₂ (88 kJ/mol) are considerably smaller than those of ( 3 )₂ and ( 4 )₂ which do not significantly differ from the ΔH° value of bitropyl (139 ± 6 kJ/mol). This finding indicates that the gain in π-electron delocalization energies, Δ(DE)_π, upon dissociation markedly increases on going from bitropyl, ( 3 )₂ and ( 4 )₂ to ( 1 )₂ and ( 2 )₂, and thus points to an additional ‘resonance stabilization’ of 1 · and 2 ·, as compared with 3 · and 4 ·. A more pronounced π-spin localization on the 7-membered ring is observed in 3 ·, 4 ·, and relative to the corresponding species, 1 ·, 2 ·, and . It can be interpreted in terms of simple π-perimeter models without explicitly invoking substantial homoconjugative interactions between the bridged centres in 1 ·, 2 ·, and . However, the shortcomings of these crude models do not allow one to make a clear-cut statement about the contributions of the homotropyl structures to the π-systems of these paramagnetic species. The radical dianions and exhibit considerable hyperfine splittings from one ²³Na or ³⁹K nucleus of the counter-ion, whereas for and such splittings stem from two equivalent alkali metal nuclei. This finding is readily rationalized by different geometries of the bridged annulenyls and their benzo- and naphthotropyl analogues. Hyperfine data are also given for the radical anions of 7 H-benzocycloheptene, ( 3-H )\documentclass{article}\pagestyle{empty}\begin{document}$2^{\ominus \atop \dot{}}$\end{document}, and 6 H-(2,3-naphtho)cycloheptene, ( 4-H )\documentclass{article}\pagestyle{empty}\begin{document}$2^{\ominus \atop \dot{}}$\end{document}, as well as for the radical dianion of 1,6:8,14-bismethano[15]annulenyl, 5 \documentclass{article}\pagestyle{empty}\begin{document}$2^{\ominus \atop \dot{}}$\end{document}.