Darstellung und Kristallstruktur von Cyclooktadekaschwefel,S18, und Cycloikosaschwefel,S20

Preparation and Crystal Structure of Cyclooctadecasulphur, S₁₈, and Cycloikosasulphur, S₂₀ Starting with mixtures of sulfanes and chlorosulfanes new sulfur rings S₁₈ and S₂₀. are synthesized according to The new compounds are remarkable stable. Preparation of the starting materials as well as the structure determinations by X-rays are reported.     

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.     

Effects of olefins on the thermal decomposition of propane part V. Effect of butene-2-Cis

The thermal decomposition of butene-2-cis at low conversion and its effect on the pyrolysis of propane have been studied in the temperature range 779-812 K. It was established that 2-butene decomposes in a long-chain process, with the chain cycle (Besides the radical path, the molecular reaction can also play a role in the formation of the products.) The thermal decomposition of propane is considerably inhibited by 2-butene, which can be explained by the fact that the less reactive radicals formed in the reactions between the olefin and the chain-carrying radicals regenerate the chain cycle more slowly than the original radicals in the above chain cycle or in the reactions The reactions of the 2-propyl radical are further initiation steps. The ratios of the rate coefficients of the elementary steps of the decomposition (Table III) have been determined via the ratios of the products. Estimation of the radical concentrations indicated that only the methyl, 2-propyl and methylallyl radicals are of importance in the chain termination. On the basis of the inhibition-influenced curves, the role of the bimolecular initiation steps. could be clarified in the presence of 2-butene.     

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.     

Gas-phase thermolysis of sulfur compounds. Part VIII. Chloromethyl allyl,cyanomethyl allyl, 1-cyanoethyl allyl and neopentyl allyl sulfides

The pyrolyses of four alkyl allyl sulfides with substituents on the α? C atom of the alkyl moiety have been studied in a stirred-flow system over the temperature range 340-400°C and pressures between 2 and 12 torr. The only products formed are propene and thioaldehydes. The reactions showed first-order kinetics with the rate coefficients following the Arrhenius equations: Chloromethyl allyl sulfide: Cyanomethyl allyl sulfide: 1-cyanoethyl allyl sulfide: Neopentyl allyl sulfide: The effects of these and other substituents on the reactivity is discussed in relation with the stabilization of a polar six-centered transition state. The results support a non-concerted mechanism where the 1–5 α? H atom shift is assisted by its acidic character.     

Photolysis of azomethane–propane mixtures. Arrhenius parameters for the hydrogen abstraction reactions of methyl with azomethane and with propane

Mixtures of up to 14% azomethane in propane have been photolyzed using mainly 366 nm radiation in the ranges of 323–453 K and 25–200 torr. Detailed measurements were made of the yields of nitrogen, methane, and ethane. Other products observed were isobutane, n-butane, ethene, and propene. A detailed mechanism is proposed and shown to account for the observed variation of product yields with experimental conditions. The quantum yield of the molecular process is found to be given by the temperature-independent equation The values of rate constants obtained are where the reactions are and it is assumed that the rate constant for the reaction is given by      

Pyrolysis of tetrafluorohydrazine

The pyrolysis of tetrafluorohydrazine has been studied from 578 to 791°K. The stoichiometry has been established as Reaction rates have been measured and the effects of surface area, inert gas pressure, and nitric oxide have been examined. The rate-determining step proposed is and the general rate expression obtained for this is      

Über Chalkogenolate. 86. Massenspektren von Dialkyltrithiocarbonaten

On Chalcogenolates. 86. Mass Spectra of Dialkyl Trithiocarbonates Dialkyl trithiocarbonates have been studied by means of mass spectra. The decomposition schemes are communicated.     

Über Chalkogenolate. 108. Untersuchungen über Perthiocyansäure 1. Darstellung und Eigenschaften von Perthiocyanaten

On Chalcogenolates. 108. Studies on Perthiocyanic Acid. 1. Synthesis and Properties of Perthiocyanates The perthiocyanates have been prepared by different techniques. The compounds were characterized by means of diverse methods.     

The mechanism of thermal dehydrochlorination. Pyrolysis of 1-Chloro-1-fluoroethane and 1-chloro-1, 1-difluoroethane

The thermal decompositions of 1-chloro-1-fluoroethane and 1-chloro-1,1-difluorethane at atmospheric pressure have been studied in the temperature range 500–600°C in a flow system. The dehydrochlorinations are homogenous in a carbonaceous reactor and unimolecular. The rate constants are given by and The criteria for molecular or chain processes in thermal dehydrochlorinations are discussed.     

The photochemistry of methyl cyclobutyl ketone. Part 2. Temperature dependence and the acetyl radical decomposition

Following earlier room-temperature studies, gaseous mixtures of methyl cyclobutyl ketone (MCK) diluted in argon have been photolyzed at temperatures up to 205°C. Experiments have been carried out at a variety of pressures (up to ca. 2 atm) at wavelengths of 313 nm (steady state conditions) and 308 nm (pulsed photolysis). The results are consistent with a mechanism dominated by radical-radical reactions involving acetyl, methyl, and cyclobutyl radicals. Acetyl radical processes predominate at lower temperatures while methyl radical reactions are more important at high temperatures. The results are interpreted via kinetic modelling of a mechanism in which a key role is played by the acetyl radical decomposition reaction Values for k₃ have been obtained and its temperature and pressure dependence are fitted by RRKM theory and a weak-collisional activation model to yield This high-pressure limiting Arrhenius equation is consistent with other studies in the same temperature range, but is difficult to reconcile with higher temperature investigations.     

Über Chalkogenolate. 76. Untersuchungen über Glykolkohlensäuren. 1. Alkalimetallglykolmonocarbonate und -glykolidicarbonate

On Chalcogenolates. 76. Studies on Glycol Carbonic Acids. 1. Glycol Monocarbonates and Glycol Dicarbonates of Alkali Metals The reactions between CO₂ and glycolates lead to glycol carbonates. The compounds have been prepared and characterized by different methods. The i.r. spectra have been assigned.     

Hydrogen abstraction from trichlorosilane by the trichloromethyl and 1,1-dichlorotrifluoroethyl radicals

The Arrhenius parameters for the reactions and have been measured. Reaction (2a) was generated and studied by the photolysis of tetrachloromethane in the presence of trichlorosilane and reaction(2b) by the photolysis of 1,1,1,-trichlorotrifluoroethane in the presence of trichlorosilane. The measured data are given by the expressions .     

Über Chalkogenolate. 82 [1]. N-Hydroxycarbamate und Ester der N-Hydroxycarbamidsäure und -carbimidsäure

On Chalcogenolates. 82. N-Hydroxy Carbamates and Esters of N-Hydroxy Carbamic Acid and Carbamic Acid The reaction between hydroxylammonium chloride, CO₂, and the corresponding hydroxide leads to N-hydroxy carbamates Esters of N-hydroxy carbamic acid have been prepared by reaction of N-hydroxy carbamates with alkyl bromide. – At room temperature the ethyl ester decomposes and forms the ester of N-hydroxy carbimic acid HO? N?C(OC₂H₅)₂. The prepared compounds have been characterized by different methods.     

Thermal stability of cyclohexane and 1-hexene

The mechanism and initial rates of decomposition of cyclohexane and 1-hexene have been determined from single-pulse shock-tube experiments. The main initial processes involve isomerization of cyclohexane to 1-hexene, followed by decomposition of 1-hexene. From comparative rate experiments the following rate expressions have been derived: The 1-hexene bond-braking reaction leads to an allylic resonance energy of 42.7 kJ and a heat of formation of allyl radicals of 176.6 kJ (300°K). There appear to be general relations relating the rate expressions for the decomposition of alkynes, alkanes, and alkenes. Studies on the induced decomposition of cyclohexane have also been carried out.     

The kinetics of the thermal bromination of CF3I. Determination of the bond dissociation energy D(CF3−I)

The kinetics of the thermal bromination reaction have been studied in the range of 173–321°C. For the step we obtain where θ=2.303RT cal/mole. From the activation energy for reaction (11), we calculate that This is compared with previously published values of D(CF₃?I). The relevance of the result to published work on k_c for a combination of CF₃ radicals is discussed.     

Kinetics of the pyrolyses of endo- and exo-5-methylbicyclo (2.2.2) oct-2-ene in the gas phase

The pyrolyses of endo- and exo-5-methylbicyclo (2.2.2) oct-2-ene (endo- and exo-MBO) have been studied between 608 and 679°K at pressures between 7 and 37 torr. These reactions correspond to parallel first-order eliminations of propene and ethylene: The rate constants (in sec^?1) for endo-MBO are given by and those for exo-MBO by Reaction mechanisms involving diradicals are shown to be compatible with the experimental results. The heats of formation and the entropies of endo and exo-MBO are estimated.     

Über Chalkogenolate. 141. Untersuchungen über Trimethylsilylxanthogensäure. 1. Darstellung und Eigenschaften von Trimethylsilylxanthaten

On Chalcogenolates. 141. Studies on Trimethylsilyl Xanthic Acid. 1. Synthesis and Properties of Trimethylsilyl Xanthates The trimethylsilyl xanthates have been prepared by reaction of the corresponding silanolate with carbon disulfide. The compounds were characterized by means of chemical and diverse spectroscopic methods. The existence of unstable trimethylsilyl xanthic acid has been demonstrated.     

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.     

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).