Synthesis and mass spectrum of 3-(3′-pyridinyloxymethyl)pyridine and polarography of its dialkyl diquaternary salts

3-(3′-Pyridinyloxymethyl)pyridine is prepared by reaction of 3-hydroxymethylpyridine with 3-bromopyridine and converted to the 1,1′-dimethyl and 1,1′-diethyl diquaternary salts with alkyl iodides. The salts are reduced polarographically at a potential (E_o) of about - 1.02 to - 1.10 V in the pH range of 5.5-8.5.     

L3/L2 white-line intensity ratios in the electron energy-loss spectra of 3d transition-metal oxides

The L₃/L₂ white-line intensity ratio in transition-metal oxides deviates widely from the statistical value of 2 : 1 but shows interesting systematics. In a series of oxides of a given metal, the ratio reaches a maximum for the d⁵ configuration (e.g. MnO) and a minimum for the d⁰ configuration (e.g. KMnO₄). In a series of monoxides, sesquioxides and dioxides of different metals, the ratio is again a maximum at the d⁵ configuration and decreases as the configuration changes towards d⁰ or d¹⁰. Our results, obtained by electron energy-loss spectroscopy, carried out in an electron microscope, are interpreted on an atomic mechanism involving spin-spin coupling. According to this model, the L₂ transition probability decreases in the progression d⁰ to d⁵ whereas the L₃ transition probability decreases beyond d⁵.     

Temperature-induced structural transitions and vibrational properties of microclusters: ab-initio molecular dynamics studies

We present the results of ab-initio molecular dynamics studies of selected microclusters of sodium, silicon and magnesium at finite temperatures, and especially discuss those obtained around room temperature. In particular, from the analysis of the atomic trajectories we can identify in some cases the existence of different isomers and the isomerization pathways. We have also calculated vibrational spectra at low temperatures and find that they can be used as a very sensitive structural probe also in sodium clusters, where the electronic properties are quite insensitive to the geometry.     

Prediction of chromatographic parameters for some anilines by molecular connectivity

Summary The possible relation existing between R_F values obtained by thin-layer chromatography for a group of anilines with connectivity indices proposed by Kier and Hall has been studied. Using multivariable regression the corresponding connectivity functions, selected for their respective correlation coefficients, standard deviations, Snedecor's F and Student's t were obtained. Regression analysis of the connectivity functions gives a correct prediction of the experimental elution sequence for this group of substances on silica gel stationary phases and various mobile phases of different polarity. The corresponding random and stability studies of the different prediction models selected were carried out, showing good stability and null randomness in all cases.     

Synthèse stéréospécifique récurrente de structures apparentées à celle de l'hormone juvénile de Hyalophora cecropia

A stereospecific synthesis of Hyalophora cecropia juvenile hormone analogs is proposed. The three double bonds are obtained successively by addition of an alkyl copper reagent to the apporpriate 1-alkyne.     

Thermochemical properties of benzoic acid derivatives VIII. Enthalpies of combustion and formation of o-, m-, and p- t-butylbenzoic acids

The enthalpies of formation in the crystalline state at 298.15 K of o-, m-, and p-t-butyl-benzoic acids have been determined by static-bomb calorimetry. Vapour-pressure determinations were made by the Knudsen-effusion technique and the sublimation enthalpies at the mean temperatures of the measurement ranges have been derived for the three acids. The values obtained are:

     

997.

Die Kristallstruktur von Ammonium-dioxodifluorovanadat     

R. Mattes  H. Rieskamp 《无机化学与普通化学杂志》1973,399(2):205-210

The Crystal Structure of NH₄VO₂F₂ Crystals of NH₄VO₂F₂ are monoclinic, space group Pc, a = 4.814(2), b = 11.434(3), c = 7.214(2) Å, β = 108.84(4)°. Z = 4. The VO₂F-ion is polymeric. The structure consists of endless chains of strongly distorted octahedra with common edges. Two adjacent polyhedra are linked by an asymmetrical oxygen bridge (bond lengths 1.74 and 2.21 Å) and an asymmetrical fluorine bridge (bond lengths 1.97 und 2.21 Å). The terminal V? O- and V? F-distances are 1.55 and 1.86 Å, respectively.     

998.

Electro-optic scattering from nitrocellulose solutions     

B.R. Jennings  J.F. Schweitzer 《European Polymer Journal》1974,10(6):459-464

Measurements have been made of the light intensity scattered from dilute solutions of a sample of nitrocellulose ($\text{M}{}_{\mathrm{w}}\text{= 460,000}$) in acetone, both in the absence and presence of a.c. and d.c. electric fields. In an earlier study, owing to a mathematical slip and a false interpretation of an experimental parameter, other workers [5] interpreted similar measurements in terms of a freely rotating polar chain model. It is shown herein that this cannot be so and that the molecules of nitrocellulose of this order of molecular weight and in this type of solvent are better regarded as extremely stiff and extended.     

999.

Zur theoretischen interpretation entgegengesetzter substituenteneffekte auf die 29Si-NMR-chemische verschiebung in substituierten trifluorphenyl- und trimethylphenyl-silanen     

R. Radeglia  G. Engelhardt 《Journal of organometallic chemistry》1974,67(2):C45-C47

Bond lengths in the gold(III) cation trans-[{(p-MeC₆H₄NH)₂C}₂AuI₂]⁺, determined by X-ray crystal structure analysis, indicate that the carbenoid ligands exert an appreciable trans influence on each other.     

1000.

Some viscoelastic properties of siloxane polymers during irradiation     

R. K. Jenkins 《Journal of Polymer Science.Polymer Physics》1966,4(1):41-52

The dynamic moduli, E′ dyn, and loss tangents, tan δ, of polydimethylsiloxane and polydimethyldiphenylsiloxane polymers have been investigated by an in situ technique during γ-irradiation. These viscoelastic properties were calculated and plotted as a function of irradiation exposure time by measuring the free end displacements and resonance frequencies of polymeric cantilever reeds. The reeds were swept through a small frequency range from about 20 to 100 cycles/sec. The moles of effectively elastic chains per unit volume (v) of the two unfilled polysiloxahes were calculated from in situ modulus data and compared to values obtained utilizing the swelling technique. The approximate molecular weights between entanglements, M_e, of these unfilled polymers were determined by extrapolation of moduli data to zero radiation exposure. The addition of a large silica filler, SiO₂, into the polymers did not alter the crosslinking rates, and the filler did not enter into polymer—filler bonding.     

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	$\text{ΔH}{}_{\mathrm{f}}{}^{\mathrm{o}}\text{(c, 298.15 K)/kJ mol}{}^{\mathrm{?1}}$	$\text{ΔH}{}_{\mathrm{s}}\text{/kJ mol}{}^{\mathrm{?1}}$
o-t-butylbenzoic acid	476.2 ± 1.9	99.8 ± 0.4	(at 314.6 K)
m-t-butylbenzoic acid	504.3 ± 1.6	103.0 ± 0.5	(at 326.5 K)
p-t-butylbenzoic acid	502.9 ± 1.7	103.8 ± 0.4	(at 334.1 K)

Die Kristallstruktur von Ammonium-dioxodifluorovanadat

The Crystal Structure of NH₄VO₂F₂ Crystals of NH₄VO₂F₂ are monoclinic, space group Pc, a = 4.814(2), b = 11.434(3), c = 7.214(2) Å, β = 108.84(4)°. Z = 4. The VO₂F-ion is polymeric. The structure consists of endless chains of strongly distorted octahedra with common edges. Two adjacent polyhedra are linked by an asymmetrical oxygen bridge (bond lengths 1.74 and 2.21 Å) and an asymmetrical fluorine bridge (bond lengths 1.97 und 2.21 Å). The terminal V? O- and V? F-distances are 1.55 and 1.86 Å, respectively.     

Electro-optic scattering from nitrocellulose solutions

Measurements have been made of the light intensity scattered from dilute solutions of a sample of nitrocellulose ($\text{M}{}_{\mathrm{w}}\text{= 460,000}$) in acetone, both in the absence and presence of a.c. and d.c. electric fields. In an earlier study, owing to a mathematical slip and a false interpretation of an experimental parameter, other workers [5] interpreted similar measurements in terms of a freely rotating polar chain model. It is shown herein that this cannot be so and that the molecules of nitrocellulose of this order of molecular weight and in this type of solvent are better regarded as extremely stiff and extended.     

Zur theoretischen interpretation entgegengesetzter substituenteneffekte auf die 29Si-NMR-chemische verschiebung in substituierten trifluorphenyl- und trimethylphenyl-silanen

Bond lengths in the gold(III) cation trans-[{(p-MeC₆H₄NH)₂C}₂AuI₂]⁺, determined by X-ray crystal structure analysis, indicate that the carbenoid ligands exert an appreciable trans influence on each other.     

Some viscoelastic properties of siloxane polymers during irradiation

The dynamic moduli, E′ dyn, and loss tangents, tan δ, of polydimethylsiloxane and polydimethyldiphenylsiloxane polymers have been investigated by an in situ technique during γ-irradiation. These viscoelastic properties were calculated and plotted as a function of irradiation exposure time by measuring the free end displacements and resonance frequencies of polymeric cantilever reeds. The reeds were swept through a small frequency range from about 20 to 100 cycles/sec. The moles of effectively elastic chains per unit volume (v) of the two unfilled polysiloxahes were calculated from in situ modulus data and compared to values obtained utilizing the swelling technique. The approximate molecular weights between entanglements, M_e, of these unfilled polymers were determined by extrapolation of moduli data to zero radiation exposure. The addition of a large silica filler, SiO₂, into the polymers did not alter the crosslinking rates, and the filler did not enter into polymer—filler bonding.