Thermophysics of alkali and related azides II. Heat capacities of potassium,rubidium, cesium,and thallium azides from 5 to 350 K

The heat capacities of potassium, rubidium, cesium, and thallium azides were determined from 5 to 350 K by adiabatic calorimetry. Although the alkali-metal azides studied in this work exhibited no thermal anomalies over the temperature range studied, thallium azide has a bifurcated anomaly with two maxima at (233.0±0.1) K and (242.04±0.02) K. The associated excess entropy was 0.90 cal_th K^?1 mol^?1. The thermal properties of the azides and the corresponding structurally similar hydrogen difluorides are nearly identical. Both have linear symmetrical anions. However, thallium azide shows a solid-solid phase transition not exhibited by thallium hydrogen difluoride. At 298.15 K the values of C_p^o, S^o, and $\text{?{G}{}^{\mathrm{o}}\text{(T)?H}{}^{\mathrm{o}}\text{(0)}}\text{T}$, respectively, are 18.38, 24.86, and 12.676 cal_th K^?1 mol^?1 for potassium azide; 19.09, 28.78, and 15.58 cal_th K^?1 mol^?1 for rubidium azide; 19.89, 32.11, and 18.17 cal_th K^?1 mol^?1 for cesium azide; and 19.26, 32.09, and 18.69 cal_th K^?1 mol^?1 for thallium azide. Heat capacities at constant volume for KN₃ were deduced from infrared and Raman data.     

The stoichiometric hydrogenation of 1,1-diphenylethylene with hydridocobalt tetracarbonyl; differences from the hydroformylation reaction

The kinetics of the stoichiometric hydrogenation of 1,1-diphenylethylene with HCo(CO)₄ is cleanly second order, permitting a determination of the activation parameters. The rate is unaffected by the atmosphere over the reaction and is enhanced by substituting DCo(CO)₄ for HCo(CO)₄. These results contrast sharply with those secured in the hydroformylation of 1-alkenes and thus dual mechanistic pathways are available for the reaction of HCo(CO)₄ with unsaturated systems. It is very possible that the stoichiometric hydrogenation of 1,1-diphenylethylene involves a geminate free radical pair but definitive proof is still lacking.     

Heat capacity and thermodynamic properties of the alkali metal compounds in the temperature range 300–800 K. I. Cesium and rubidium molybdates

The heat capacities of cesium and rubidium molybdates, Cs₂MoO₄ and Rb₂MoO₄, have been measured by differential scanning calorimetry (DSC) in the temperature range 300–800 K. These values have been combined with published low-temperature heat capacity data for Cs₂MoO₄ to obtain thermodynamic functions to 800 K. For Rb₂MoO₄, however, these functions could not be calculated because low-temperature heat capacities are unavailable. Instead, only heat capacity data are reported.     

The stoichiometric hydrogenation of 9-methylidenefluorene and related compounds with hydridocobalt tetracarbonyl

9-Methylideneflourene (IIa) reacts rapidly with HCo(CO)₄ at -67° C to give a quantitative yield of 9-methylfluorene (IIIa); k₂  (13.4 ± 0.5) × 10^-2 l mol^-1_S^-1. Although the internal olefin, 9-ethylidenefluorene (IIb) reacts more slowly than IIa, it is hydrogenated about 2.5 times as fast as the terminal olefin, 1,1-diphenylethylene (I). Measurement of the rate of the reaction of IIb with DCo(CO)₄ and comparison with HCo(CO)₄ shows a very large inverse isotope effect k_H/k_D of 0.43.     

The stoichiometric hydrogenation of substituted phenyl alkenes by hydridocobalt tetracarbonyl

The relative rates of hydrogenation of a series of styrenes, phenylpropenes, 1,1-diphenylethylenes, and 1,1-diphenylpropenes were measured. Compared to 1,1-diphenylethylene (k₂ = 2.42 X 10^-2 I mol^-1 sec^-1), 1,1-diphenylpropene and styrene have relative rates of 0.0045 and 0.011 respectively. The effect of 4-chloro and 4-methoxy substituents on both styrene and diphenylethylene is slightly rate enhancing. An unusual kinetic dependence occurs with mixtures of alkenes.     

On the use of electron paramagnetic resonance to implement thermogravimetry data: the thermal decomposition of zinc oxalate dihydrate

The complementary use of thermogravimetric analysis and electron paramagnetic resonance spectroscopy enables the identification on interrelated and successive steps in the vacuum decomposition of ZnC₂O₄ · 2H₂O. After completion of the oxalate dehydration, CO adsorbed species (analogous to those previously reported on MgO) are observed by EPR, starting at a temperature of 250°C. In the temperature range 250–350°C, the CO ad-species disappear while paramagnetic ZnO_1?x and possibly CO^?₄ entities are formed. It is proposed that the latter stems from the reaction of oxygen released by the decomposition of ZnO with CO₂ produced during the oxalate decomposition. Above 300°C, ZnO_1?x and CO^?₄ disappear, leading to the formation of O^3?₃ centers. The latter are gradually decomposed between 350 and 575°C, releasing O₂ observed in EPR as O^?₂ molecular anions and trapped electrons which are again detected as ZnO_1?x. A partially reduced ZnO phase is most probably the end-product of the decomposition.     

Mechanism and reaction rate of the karl-fischer titration reaction: Part III. Rotating ring-disk electrode measurements— comparison with the aqueous system

A platinum disk-platinum ring electrode was used to investigate the oxidation of sulfur dioxide by iodine and triiodide in aqueous solutions. Contrary to methanolic solutions, where the monomethyl sulfite ion is the only oxidizable species, in aqueous solutions both the hydrogen sulfite ion and the sulfite ion can be oxidized. The reaction rate was generally so high, that the method for measurements of homogeneous second order reactions had to be used. At pH values >5, the reaction proceeded too fast to be measured reliably. In a solution “diluted” with ethanol (50% of weight), however, the reaction rate was within the range where a rotating ring-disk electrode can be applied to measure fast homogeneous reactions. At very low pH values both the first order calculation technique and the second order method could be used. The results with both methods were in fair agreement.     

The thermodynamic properties of acetals+heptane mixtures at 298.15 K

Excess enthalpies and excess volumes were determined at 298.15 K for: dimethoxymethane+heptane, diethoxymethane+heptane, 1,1-dimethoxyethane+heptane, 1,1-diethoxyethane+heptane, 2,2-dimethoxypropane+heptane and 1,1-diethoxypropane+heptane.     

Heat capacity and thermodynamic functions of MnBr2 · 4D2O and MnCl2 · 4D2O

The heat capacities of MnBr₂ · 4D₂O and MnCl₂ · 4D₂O have been experimentally determined from 1.4 to 300 K. The smoothed heat capacity and thermodynamic functions (H°_TH°₀) and S°_T are reported for the two compounds over the temperature range 10 to 300 K. The error in the thermodynamic functions at 10 K is estimated to be 3%. Additional error in the tabulated values arising from the heat capacity data above 10 K is thought to be less than 1%. A λ-shaped heat capacity anomaly was observed for MnCl₂ · 4D₂O at 48 K. The entropy associated with the anomaly is 1.2 ± 0.2 J/mole K.     

Studies of Ziegler-type catalysts for the polymerization of ethylene and propylene II The polymerization of ethylene with VOCl3-Et3Al2Cl3 (chlorinated activator) catalysts

VOCl₃-Et₃Al₂C1₃(chlorinated activator) catalysts have been employed for the polymerization of ethylene at T between 15 and 85° in n-hexane. Using butylperchlorocrotonate as the activator, the following catalyst efficiencies (g polymerization, hr, atmosphere ethylene in the cap gas) were achieved: 10^6,1 MFI = 0-00; 10^5,8, e.g. MFI = 1 0 (with 9 per cent H₂ present in the cap gas) and 10^6–9 MFI = 0?4 (with 44 mmole/1 styrene in the hexane medium). Reactions between the aluminium alkyl and the activator molecules produced other chlorinated species of high average activator effectiveness. The catalyst system could be reactivated by further additions of Et₃Al₂Cl₃. The minimum value of the polymerization propagation rate constant is estimated to be 10¹²²?6x10,461 cm³/mole sec.     

Standard potentials of silver-silver bromide electrode and related thermodynamic quantities in (5, 10 and 15 wt-%) 2-butanol-water mixtures

The standard potentials of silver-silver bromide electrode in 5, 10 and 15 wt.-% 2-butanol have been determined from e.m.f. measurements of a cell of the type: Pt(or Pd), H₂(g)|HBr(m), 2-butanol-water mixtures| AgBr, Ag at temperatures 15°, 25° and 35°C and in the molality range of HBr from 0.003 to 0.1 mol kg^?1. Standard potentials were utilized to calculate: (1) the standard thermodynamic quantities for the cell reaction and for the reaction of HBr formation, (2) the mean activity coefficients of HBr, and (3) the standard thermodynamic quantities for transfer of HBr from water to 2-butanol-water mixtures. The thermodynamic functions for the transfer process have been interpreted in regard to the acid-base properties and structure of the solvents.     

The phase diagram for the binary system K2CrO4CaCrO4

The phase diagram for the binary system K₂CrO₄CaCrO₄ has been determined for CaCrO₄ concentrations up to 60 mole%, using the techniques of differential thermal analysis, X-ray diffraction, and drop calorimetry. Essential features of the phase diagram are: the solid-solid phase transition for pure K₂CrO₄ at 670°C, β-K₂CrO₄ ? α-K₂CrO₄; a eutectoid reaction at 14 mole% CaCrO₄ and 548°C, β-K₂CrO₄ ? α-K₂CrO₄ + K₂CrO₄ · CaCrO₄; a peritectoid event at 50 mole% CaCrO₄ and 640°C, β-K₂CrO₄ + CaCrO₄ ? K₂CrO₄ · CaCrO₄; and a eutectic reaction at 51 mole% CaCrO₄ and 678°C, L ? β-K₂CrO₄ + CaCrO₄. X-ray diffraction studies lead to the determination of the unit cell dimensions for the K₂CrO₄ · CaCrO₄ double salt, a C-centered monoclinic form with a₀ = 7.615(6) Å, b₀ = 22.797(15) Å, c₀ = 9.777(9) Å, β = 115.45(5)°.     

Infrared spectra of Cs3CoCl5

The infrared spectra, transmittance, and polarized reflectance of Cs₃CoCl₅ are reported. The group theoretical analysis was executed and a vibrational assignment proposed on the basis of D_4h symmetry. Factor group and site effects are discussed.     

Studies on constituents of Abies grandis: The structures and absolute stereochemistry of cyclograndisolide and epicyclograndisolide,novel cyclopropane triterpene lactones

The light petroleum extract of grand fir [Abies grandis (Dougl.) Lindl.] was found to contain two novel triterpene lactones. The first compound, named cyclograndisolide, was shown by chemical and spectroscopic considerations and finally confirmed by X-ray analysis to be (23 R)-3α-methoxy-9,19-cyclo-9β-lanost-24-ene-26,23-olide (6). The second component, epicyclograndisolide was isomeric with the first and was assigned as (23 S)-3α-methoxy-9,19-cyclo-9β-lanost-24-ene-26,23-olide (10).     

Ambient pressure synthesis,properties, and structure refinements of VP4 and CoP2

The previously reported compounds VP₄ and CoP₂, prepared at high pressure, were synthesized in well-crystallized form at ambient pressure by reaction of the elemental components in the presence of iodine. Their structures were refined from single-crystal X-ray diffractometer data to conventional residuals of R = 0.033 for VP₄ (CrP₄ type structure, 11 variables, 815 F values) and R = 0.019 for CoP₂ (arsenopyrite structure, 14 variables, 932 F values). VP₄ is paramagnetic and a metallic conductor. CoP₂ is a diamagnetic semiconductor with an activation energy of 0.34 eV. Chemical bonding and potential displacive phase transitions of these compounds are discussed.     

The preparation and properties of dicarbonyl-h5-cyclopentadienyliron h2-vinyl ether and h2-ketene acetal complexes

Metallation of >-haloacetals wth sodium dicarbonyl-h⁵-cyclopentadienyl- ferrate (Fp^-) provides a convenient point of departure for the synthesis of alhyde -iron complexes (FpCHRCHO) and of h²-vinyl alcohol and vinyl ether cations [Fp(CH₂=CHOR)]⁺. These latter complexes are shown to be best described as distorted dihapto cation. Treatment of FpCOCH₂OMe with strong acid leads to the ketene hemiacetal cation [Fp(CH₂=C(OH)OMe)]⁺ rather than to the expected ketene complex. This substance, as well as the acetal cation [Fp(CH₂=C(OMe)OEt)]⁺ prepared by alkylation of FpCH₂COOMe, may possess the structure of an h¹-metal complex incorporating a carboxonium ion. A correlation is shown to exist between the chemical shift of cyclopentadienyl protons and the average infrared carbonyl stretching frequency in a variety of Fp(olefin)⁺ FpR complexes.