Beiträge zur Chemie der Oxidhalogenide von Molybdän und Wolfram. V. Molybdänoxidtetrachlorid und Molybdänoxidtrichlorid

The formation enthalpies were ascertained from the solution enthalpies in 2 n NaOH resp. 2 n NaOH + 1% H₂O₂. The results of equilibrium measurements in the systems give the formation enthalpies and standard entropies: . The value of the standard entropy of the gaseous MoOCl₄ was estimated to be 91 (±3) cl. From the enthalpies and entropies of sublimation the values were obtained.     

Reactions of alkoxy radicals with O2. I. C2H5O radicals

C₂H₅ONO was photolyzed with 366 nm radiation at ?48, ?22, ?2.5, 23, 55, 88, and 120°C in a static system in the presence of NO, O₂, and N₂. The quantum yield of CH₃CHO, Φ{CH₃CHO}, was measured as a function of reaction conditions. The primary photochemical act is and it proceeds with a quantum yield ?_1a = 0.29 ± 0.03 independent of temperature. The C₂H₅O radicals can react with NO by two routes The C₂H₅O radical can also react with O₂ via Values of k₆/k₂ were determined at each temperature. They fit the Arrhenius expression: Log(k₆/k₂) = ?2.17 ± 0.14 ? (924 ± 94)/2.303 T. For k₂ ? 4.4 × 10^?11 cm³/s, k₆ becomes (3.0 ± 1.0) × 10^?13 exp{?(924 ± 94)/T} cm³/s. The reaction scheme also provides k_8a/k₈ = 0.43 ± 0.13, where      

The kinetics of the reactions of C2F5 radicals with Br2 and HBr

A mixture of Br₂ + HBr + C₂F₅I was photolyzed in the vapor phase. The reaction forms C₂F₅ radicals which are removed by Competitive studies over the range of 74–146°C gave ratios of k₁₀/k₉, and these were combined with values obtained previously by different methods at higher temperatures upto 515°C to give where θ = 2.303RT J/mol. A value is assigned to the activation energy E₁₀, and this, with other data, leads to at 25°C. This result is in excellent agreement with two previous independent determinations.     

Lösungsthermodynamik von FeCl2 in Mischschmelzen aus Alkalichloriden und LaCl3 bzw. CeCl3

Solution Thermodynamics of FeCl₂ in Molten Mixtures of Alkaline Chlorides and LaCl₃ or CeCl₃ Activity coefficients and the chemical excess potential of FeCl₂ dissolved in molten chloride mixtures were determined by EMF measurements with galvanic cells of the type in the concentration range from 0.01–5 mole-% at 720 and 820°C. An average cationic potential is defined and used to calculate a distance parameter () for the different solvent melt mixtures. may be estimated by equations of the type      

Über Chalkogenolate. 121. Untersuchungen über N-Cyanomonothiocarbimidsäure 1. Darstellung und Eigenschaften von Alkalimetall-N-cyanomonothiocarbimaten

On Chalcogenolates. 121. Studies on N-Cyanomonothiocarbimic Acid. 1. Synthesis and Properties of Alkali Metal N-Cyanomonothiocarbimates The hitherto unknown N-cyanomonothiocarbimates M₂[SOC?N? CN] · H₂O, where M = Na, K, Rb, Cs, have been prepared by reaction of the corresponding alkali metal salt of cyanamide with COS. N-Cyanomonothiocarbimates react with sulfur to form the ion, which gives with an acid and with CH₃I the methyl compound . The reaction of the latter compound with H₂O₂ yields . All compounds have been characterized by means of diverse methods.     

Zum chemischen Transport im System Mn?O unter Berücksichtigng des Sauerstoffkoexistenzdruckes (I)

Chemical Transport in the System Mn? O in Consideration of the Oxygen Coexistence Pressure (I) The chemical transport of the coexistent phases Mn₂O₃? Mn₃O₄ and Mn₃O₄? MnO with Cl₂, Br₂, I₂, HCl, HBr, and HI was analysed thermodynamically and experimentally. The mentioned transport agents are able to transport the following phases:

1 Index (o) bedeutet obere, (u) untere Phasengrenze (index (o) – upper phase boundary, (u) – lower phase boundary).

.     

The determination of the arrhenius parameters for the reaction Cl + C2F5I → ICl + C2F5 using a competitive method

The reactions have been studied competitively over the range of 28–182°C by photolysis of mixtures of Cl₂ + C₂F₅I+ CH₄. We obtain where θ = 2.303RT J/mol. The use of published data on reaction (2) leads to log (k₁cm³/mol sec) = (13.96 ± 0.2) ? (11,500 ± 2000)/θ.     

Chlorine-photosensitized reactions in the Cl2 + O2 + 1,1,1,2-C2H2Cl4 system

The gas-phase photochlorination (λ = 436 nm) of the 1,1,1,2-C₂H₂Cl₄ has been studied in the absence and the presence of oxygen at temperatures between 360 and 420°K. Activation energies have been estimated for the following reaction steps: The dissociation energy D(CCl₃CHCl? O₂) ± (24.8 ± 1.5) kcal/mole has also been estimated from the difference in activation energy of the direct and reverse reactions The mechanism is discussed and the rate parameters are compared to those obtained for a series of other chlorinated ethanes.     

H2S-promoted thermal isomerization of cis-2-pentene to 1-pentene and trans-2-pentene around 800 K

H₂S accelerates the thermal isomerization of cis-2-pentene (P2c) to 1-pentene (P1) and trans-2-pentene (P2t) to around 800 K. This effect is interpreted on the basis of a free radical mechanism in which 2-pentenyl and thiyl radicals are the main chain carriers. P1 formation is essentially explained by the competing processes: P2t formation is due to addition-elimination processes: the importance of which has been evaluated against process (?4μ): The following ratios of rate constants have been measured and are discussed: (RT in cal mol^?1).     

A shock tube study of the reactions of NH with NO,O2, and O

The reactions of NH(X³Σ⁻) with NO, O₂, and O have been studied in reflected and incident shock wave experiments. The source of NH in all the experiments was the thermal dissociation of isocyanic acid, HNCO. Time-histories of the NH(X³Σ) and OH(X²Π) radicals were measured behind the shock waves using cw, narrow-linewidth laser absorption at 336 nm and 307 nm, respectively. The second-order rate coefficients of the reactions: were determined to be: and cm³ mol⁻¹ s⁻¹, where ƒ and F define the lower and upper uncertainty limits, respectively. The branching fraction of channel defined as k_3b/k_3total, was determined to be 0.19 ± 0.10 over the temperature range of 2940 K to 3040 K.     

The reactions of alkoxy radicals with O2. II. n-C3H7O radicals

n-C₃H₇ONO was photolyzed with 366 nm radiation at ?26, ?3, 23, 55, 88, and 120°C in a static system in the presence of NO, O₂, and N₂. The quantum yields of C₂H₅CHO, C₂H₅ONO, and CH₃CHO were measured as a function of reaction conditions. The primary photochemical act is and it proceeds with a quantum yield ?₁ = 0.38 ± 0.04 independent of temperature. The n-C₃H₇O radicals can react with NO by two routes The n-C₃H₇O radical can decompose via or react with O₂ via Values of k₄/k₂ ? k_4b/k₂ were determined to be (2.0 ± 0.2) × 10¹⁴, (3.1 ± 0.6) × 10¹⁴, and (1.4 ± 0.1) × 10¹⁵ molec/cm³ at 55, 88, and 120°C, respectively, at 150-torr total pressure of N₂. Values of k₆/k₂ were determined from ?26 to 88°C. They fit the Arrhenius expression: For k₂ ? 4.4 × 10^?11 cm³/s, k₆ becomes (2.9 ± 1.7) × 10^?13 exp{?(879 ± 117)/T} cm³/s. The reaction scheme also provides k_4b/k₆ = 1.58 × 10¹⁸ molec/cm³ at 120°C and k_8a/k₈ = 0.56 ± 0.24 independent of temperature, where      

Organische Phosphorverbindungen XXIX. Eine neue Methode zur Darstellung von dialkylaminomethylsubstituierten Phosphonig- und Phosphinsäuren der allgemeinen Formel R2NCH2PH(O)OH und (R2NCH2)2P(O)OH [1]

A new method for the preparation of dialkylaminomethyl-phosphonous and-phosphinic acids, R₂NCH₂P(O)H(OH) and (R₂NCH₂)₂P(O)OH, is described. This involves reaction of hypophosphorous acid with hydroxymethyl-dialkyl-amines or a mixture of formaldehyde and a secondary amine. and The crystalline acids form monohydrates which are stable up to the melting points of the acids. The IR. and ³¹P-NMR. spectra are reported.     

Thermal stability of alcohols

3,3-Dimethylbutanol-2 (3,3-DMB-ol-2) and 2,3-dimethylbutanol-2 (2,3-DMB-ol-2) have been decomposed in comparative-rate single-pulse shock-tube experiments. The mechanisms of the decompositions are The rate expressions are They lead to D(iC₃H₇? H) – D((CH₃)₂(OH) C? H) = 8.3 kJ and D(C₂H₅? H) – D(CH₃(OH) CH? H) = 24.2 kJ. These data, in conjunction with reasonable assumptions, give and The rate expressions for the decomposition of 2,3-DMB-1 and 3,3-DMB-1 are and      

Kinetics and the mechanism of the thermal reaction between trifluoromethylhypofluorite and hexafluoropropene

The kinetics of the thermal reaction between CF₃OF and C₃F₆ have been investigated between 20 and 75°C. It is a homogeneous chain reaction of moderate length where the main product is a mixture of the two isomers 1-C₃F₇OCF₃ (68%) and 2-C₃F₇OCF₃ (32%). Equimolecular amounts of CF₃OOF₃ and C₆F₁₄ are formed in much smaller quantities. Inert gases and the reaction products have no influence on the reaction, whereas only small amounts of oxygen change the course of reaction and larger amounts produce explosions. The rate of reaction can be represented by eq. (I): The following mechanism explains the experimental results: Reaction (5) can be replaced by reactions (5a) and (5b), without changing the result: Reaction (4) is possibly a two-step reaction: For ∣CF₃ = ∣C₃F₆∣, ν_20°C = 36.8, ν_50°C = 24.0, and ν_70°C = 14.2.     

Über Chalkogenolate. 126. Untersuchungen über N-Cyanformamidinodithiocarbimidsäure 2. Thermisches Verhalten von Kalium-N-cyanformamidinodithiocarbimat in Lösung

On Chalcogenolates. 126. Studies on N-Cyanformamidino Dithiocarbimic Acid. 2. Thermal Behaviour of Potassium N-Cyanformamidino Dithiocarbimate in Solution The thermal treatment of K₂[S₂C?N? C(NH₂)?N? CN] in methanolic solution yields . The semi-hydrate has been isolated. It reacts with acid to form The reaction with H₃CI gives The compounds have been characterized by means of electron absorption, ¹H- and ¹³C-N.M.R., infrared, and mass spectra.     

The kinetics of the thermal gas-phase reaction Br2 + C6F5I → BrI + C6F5Br. An attempt to determine the bond dissociation energy D(C6F5-I)

The kinetics of the thermal bromination reaction have been studied in the range of 261°–391°C. The observed rate law is compatible with initiation by the step for which we obtain where Θ = 2.303RT cal/mol. Using the above value of E₆, we have This result disagrees with values of D(C₆F₅-I) obtained in other ways and we conclude that reaction (3) probably does not involve initiation by reaction (6). Instead, initiation may involve an addition of Br to the ring in C₆F₅I followed by decomposition of the adduct to give C₆F₅Br. If correct, this implies that the Arrhenius parameters above refer to the addition reaction rather than to reaction (6).     

Interaction between CO and O

The reaction between carbon monoxide and atomic oxygen was studied in a gas flow over a temperature range of 136 to 230°C at atmospheric pressure. The rate constant of this reaction, considered to be one for a second-order reaction, was found to decrease with increasing temperature and to depend on the ratio of O₂ to CO that was varied from 0.11 to 2.69. A conclusion was made that under the experimental conditions the reaction was third order The rate constant of this reaction was determined for a mixture of O₂ and CO and it was found that the efficiency of O₂ as particle M is four times that of CO.     

Beiträge zum thermischen Verhalten von Oxoniobaten der Übergangsmetalle. IV. Zum Chemischen Transport von CoNb2O6 mit Cl2, NH4 und HgCl2. Experimente und Modellrechnungen

Contributions on the Thermal Behaviour of Oxoniobates of the Transition Metals. IV The Chemical Vapour Transport of CoNb₂O₆ with Cl₂, NH₄Cl, or HgCl₂. Experiments and Calculations Well shaped crystals of CoNb₂O₆ were obtained by CVT using Cl₂ (added as PtCl₂), NH₄Cl or HgCl₂ as transport agents (1020°C → 960°C). As a result of thermodynamic calculations the evaporation and deposition of CoNb₂O₆ in the presence of Cl₂ can be expressed by the heterogenous endothermic equilibrium (1). The endothermic reaction (2) is responsible for the CVT of CoNb₂O₆ if NH₄Cl is used as transport agent: The unfavourable site of the equilibrium (3) causes the small transport effect using HgCl₂ as transport agent. Assuming Δ_BH°₂₉₈(CoNb₂O_6,s) = ?524.7 kcal/mol a satisfying agreement between thermodynamical calculation and experimental results can be reached.     

Thermochemische Untersuchungen im System V/Nb/O. II Zum chemischen Transportverhalten im Bereich V2O5/Nb2O5/VO2/NbO2

Thermochemical Investigations in the System V/Nb/O. II. Chemical Transport in the Region V₂O₅/Nb₂O₅/VO₂/NbO₂ Transport experiments were used to support the phase relationships of the V₂O₅/Nb₂O₅/VO₂/NbO₂ system, which were established by annealing experiments of powder mixtures. The phase relations were studied in the NbO₂-rich region of the system by means of X-ray and ESMA methods. The NbO₂-rich section is characterized by the following two phase and three phase regions: Two phase region: V₃Nb₉O₂₉/rutile mixed crystal V_1?xNb_xO₂ Two phase region: BI-mixed crystal/V_xNb_1?xO₂ Three phase region: V₃Nb₉O₂₉/solubility limit LG1 (V_1?xNb_xO₂)/BI-mixed crystal Three phase region: solubility limit LG1 (V_1?xNb_xO₂)/BI-mixed crystal/solubility limit LG2 (V_xNb_1?xO₂). The composition of the solubility limits LG1 and LG2 was ascertained by means of ESMA-investigation: LG1: 57.5 ± 5 mol% NbO₂/43.5 ± 5 mol% VO₂ LG2: 22.5 ± 5 mol% NbO₂/78.5 ± 5 mol% VO_2?     

Silicium-Komplexe. VI. Oxalato-silicate und Oxalato-germanate

Silicon complexes. VI. Oxalatosilicates and oxalatogermanates By reaction of SiCl₄(GeCl₄) or diaryldichloro silanes (germanes) with Ag₂C₂O₄ and quartary ammonium or phosphonium iodides, compounds of the following formulas were prepared: These products are resistant towards hydrolysis and were characterized by IR-spectra, conductivity and thermal decomposition. The compounds resulting from reaction of monoorganitrichloro silanes nearly correspond to the formula and are extremely sensitive towards hydrolysis.