The reactions of methyl radicals with chloromethanes

The reaction of methyl radicals with CCl₄ and CCl₃Br have been reinvestigated in the gas phase over a wide range of temperatures and pressures using both the photolysis of acetone and the pyrolysis of di-tertiary butyl peroxide (dtBP) as the methyl radical sources. The results are in essential agreement with previous work; however, these new studies provide evidence that at higher pressures the major source of HCl in the reactions is due to methyl radical attack on CH₃CCl₃, formed via the combination of methyl and trichloromethyl radicals. From these investigations Arrhenius parameters for the reactions have been determined: Pyrolysis of dtBP in the presence of relatively high-pressure mixtures of CCl₄ and CCl₃Br resulted in no enhanced methane formation, since, under these conditions, the only termination product is C₂Cl₆, and the HCl precursor CH₃CCl₃ is not formed. A competitive technique has been used in which dtBP was pyrolysed in the gas phase in the presence of high-pressure mixtures of CCl₃Br and a chloromethane. Arrhenius parameters were obtained for the reactions and the results were used to provide information on the importance of polar effects for hydrogen abstraction from halogenated methanes.     

The kinetics of radiation-induced hydrogen abstraction by CCl3 radicals in the liquid phase: Cyclohexene

The kinetics of hydrogen abstraction from cyclohexene by CCl₃ radicals were studied in CCl₄ solution as a function of cyclohexene concentration and temperature in the range of 26–140°C. The CCl₃ radicals were produced both by radiolysis of CCl₄ and by photolysis of CCl₃Br. The rate constant for the reaction was found to be given by the equation where θ = 2.303 RT kcal/mol. This activation energy leads to C? H bond strength for the allylic hydrogen of 85 ± 1 kcal/mol, which means a resonance stabilization energy of 11 ± 1.5 kcal/mol for the C-C₆H₁₁ radical.     

Some hydrogen abstraction reactions of the CF3CCl2 radical

The gas phase photolysis of CF₃CCl₃ in the presence of several alkanes has been used to obtain Arrhenius parameters for the abstraction of hydrogen atoms by the CF₃CCl₂ radical: Activation energies of 9.6 and 8.0 kcal/mole are found for abstraction from secondary and tertiary C–H bonds, respectively. The Arrhenius parameters are compared to those for CCl₃ and CF₃ radicals.     

Synthesis of thiols,disulfides, and sulfonic acids containing trichloromethyl,dichloro vinyl,and carboxy groups

Summary Starting from...-tetrachloroalkanes, trichloroalkenes of structure CCl₂=CH(CH₂)_nCl, and-chloro carboxylic acids, we obtained ithio, mercapto, and sulfo compounds and some of their derivatives of structure; [CCl₃(CH₂)₄]₂S₂; [CCl₂=CH(CH₂)₃]₂S₂; [ROOC(CH₂)₄]₂S₂ (in which ); CCl₃(CH₂)₄SCl; CCl₃(CH₂)_nSH (in which n=4,6,8); CCl₂=CH(CH₂)₃SH; ROOC(CH₂)₄SH (in which R=H, C₂H₅); CCl₃(CH₂)_nSO₃Na (in which n=4,6,8); C₂H₅OOC(CH₂)₄SO₃Na.     

Photochemistry of acetylenic derivatives of aromatic amines. Communication 1. Photolysis products of P-ethynyl-N,N-dimethylaniline in carbon tetrachloride

Conclusions During photolysis of p-ethynyl-N,N-dimethylaniline in CCl₄, products are formed that are exclusively due to a reaction at the triple bond and amino group, without affecting the aromatic ring: p-dimethylaminoacetophenone, N-methyl-N-(p-ethynylphenyl)-carbamoyl chloride, N-methyl-N-[p-(-chlorovinylphenyl)]-carbamoyl chloride, p-dimethylamino--chlorostyrene, and p-dimethylamino-,-dichlorostyrene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1163–1166, May, 1986.     

Xenon sensitized photolysis of CCl4/CH4 mixtures

The kinetics and mechanism of energy transfer from Xe/³P₁/ atoms to CH₄ molecule was investigated by XeCl/B-X/ transition fluorescence intensity measurements in xenon sensitized photolysis of CCl₄/CH₄ mixtures. The kinetic analysis of the experimental I_B-X=f/CH₄/ relation at constant CCl₄ and xenon concentrations showed that the “third order” energy transfer reaction should be included into the reaction mechanism: $$Xe/^3 P_1 / + Xe + CH_4 \to products$$ with the rate constant /2.5±0.5/×10^?28 cm⁶s^?1.     

Photolysis of water-carbon tetrachloride and water-chlorobenzene saturated solutions and their two-phase systems. Quantum yields of chloride ions

The quantum yields of formation of chloride ions were determined in photolysis (=254 nm) of watercarbon tetrachloride organic phase of CCl₄(Cl^–)=0.89±0.04 water-chlorobenzene (_PhCl(Cl^–)=0.137± ±0.005) two-phase systems and saturated aqueous solutions of carbon tetrachloride (_CCl4(Cl^–)=18.9±5.6 and chlorobenzene _PhCl(Cl^–)=0.56±0.03. The quantum yields of chloride ions obtained from these systems are compared with partial radiation yields in the same systems. A mechanism for formation of Cl^– ions is proposed.     

The effect of inclusion on the heat capacities of some simple molecules in adducts of Dianin's compound

The heat capacities of unsolvated (empty) Dianin's compound (4p-hydroxypheny]-2,2, 4-trimethylchroman) and the ethanol and carbon tetrachloride adducts of Dianin's compound have been measured in the 30–300K temperature range. The molar heat capacities of the guest species were calculated from the experimental results and compared with molar heat capacities of bulk CCl₄ and bulk C₂H₅OH The stoichiometry of the CCl₄ adduct was determined to be six host molecules per guest CCl₄, in contrast to an earlier report.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.     

Calculation of the ultraviolet and visible absorption spectra of the complex of nickel (ii) with 1, 5-diphenylformazan

The ultraviolet and visible absorption spectra of 1,5-diphenylf ormazan and its nickel complex in acetone, ethanol, and carbon tetrachloride have been calculated. For a qualitative interpretation of the spectrum, the calculations for the molecules of the complex and the ligand were carried out by the MO LCAO method in the Mulliken-Helmholz-Wolf sberg approximation. According to the results obtained the oscillator strengths of the transitions in the spectrum of the complex decrease as the interaction of the solvents with Ni increases in the order CCl₄, C₂H₅OH, C₃H₆O. This leads to a decrease in the negative charges on the nitrogen atoms and a decrease in the oscillator strengths of the transitions between the MO including the AO of nitrogen. All the transitions are interpreted as —* transitions.     

ESR spectroscopic investigation of steric and polar factors in the addition of radicals to unsaturated compounds

The rate constants of the addition of CCl₃CH₂ClCH₃(R⁶) radicals to -methyl-styrene, styrene, methyl methacrylate, methyl acrylate, and acrylonitrile and of CCl₃CH₂(CH₃)₂(R⁷) radicals to styrene, methyl acrylate, and acrylonitrile were determined by ESR spectroscopy. It was shown that the radicals R⁶ and R⁷ possess approximately equal reactivity in addition to unsaturated compounds, despite the difference in the donor-acceptor properties of the substituents at the vinyl group. In a comparison of the reactivity of radicals R⁶ and R⁷ with the reactivity of radicals CCl₃CH₂H₂(R¹), CCl₃CH₂HCH₃(R³), CCl₃CH₂HCl(R⁴), and ClCH₂CH₂Cl₂(R⁵) [1] in addition reactions, it was shown that polar and steric effects of the substituents situated in the -position to the radical site of the above-mentioned radicals, as well as the donor-acceptor properties of the substituents at the vinyl group in the unsaturated compounds, lead to appreciable changes in reactivity.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 136–141, January, 1992.     

Gas phase reactions of CF3, C2F5, and n-C3F7 with carbon tetrachloride

The reactions of some perfluoroalkyl radicals with carbon tetrachloride have been studied using the photolysis of the corresponding perfluoroalkyl iodide as the free radical source. The Arrhenius parameters, based on the value of 2.3 × 10¹³ cm³ mol^?1 s^?1 for the self-combination rate constant of all radicals are:

Beeinflussung der Umsetzung von Phosphor(V)-chlorid mit Isopropenylacetat durch polare Lösungsmittel

Zusammenfassung Bei der Umsetzung von PCl₅ mit Isopropenylacetat verlaufen zwei konkurrierende Reaktionen, deren Wechselbeziehung weitgehend vom Charakter des Lösungsmittels abhängt.In PCl₃- und CCl₄-Lösung^1–4 entsteht beim Erhitzen zunächst ein komplexes Anlagerungsprodukt,1 (R=R=CH₃), das durch Wanderung der Acetylgruppe in die -Stellung eine Umlagerung erfährt. Als Endprodukt (nach Behandlung des Reaktionsgemisches mit SO₂) bildet sich das Säurechlorid der -Acetyl--chlorpropenylphosphonsäure4 (3a:R=R=CH₃). Die Nebenreaktion ergibt nur unbedeutende Mengen von phosphorhaltigen niedrigsiedenden Verbindungen. In Phosphoroxychlorid- oder Thionylchloridlösung wird die Nebenreaktion, namentlich bei niederer Temperatur, zur Hauptreaktion. Das Gemisch enthält CH₃CCl₂CH₂POCl₂, CH₃CCl=CHPOCl₂ und CH₃COCH₂POCl₂, die als entsprechende Äthylester nachgewiesen wurden. In POCl₃ und SOCl₂ beim Erhitzen sowie in PCl₃ und CCl₄ bei niedriger Temp. treten beide konkurrierende Reaktionen nur mäßig in Erscheinung.

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Two competing reactions occur between PCl₅ and isopropenyl acetate; their ratio depends largely on the solvent. In PCl₃ and CCl₄ on heating a complex adduct1 (R=R=CH₃) ist first formed which undergoes rearrangement by migration of the acetyl group into the -position. The final product, after treatment of the reaction mixture with SO₂, is -acetyl--chloropropenyl phosphonic acid chloride (3a). The side reaction yields only insignificant amounts of phosphorus-containing low boiling compounds. In POCl₃ or SOCl₂ the side reaction becomes the main reaction especially at low temperatures. The mixture contains CH₃CCl₂CH₂POCl₂, CH₃CCl=CHPOCl₂ and CH₃COCH₂ POCl₂, identified as their ethyl esters. In POCl₃ and SOCl₂ on heating, and in PCl₃ and CCl₄ at low temperatures, the two competitive reactions take place only to a moderate extent.

     

Ruthenium catalysed oxidation without CCl4 of oleic acid, other monoenic fatty acids and alkenes

Ruthenium catalysed oxidation of alkenes and monoenic fatty acids is reported. The study of the influence of cosolvents (H₂O/MeCN/X) shows that toxic CCl₄ initially used in the Sharpless system (H₂O/MeCN/CCl₄) can be avoided and demonstrates that the oxidative cleavage of CC bond could be accomplished in good yields with H₂O/MeCN/AcOEt solvent system in a ratio 3/2/2, respectively.     

Effects of dipole interaction and solvation on the CO stretching band of N,N-dimethylacetamide in nonpolar solutions: Infrared, isotropic and anisotropic Raman measurements

The concentration dependence of the CO stretching (ν_CO) band of N,N-dimethylacetamide (NdMA) in cyclohexane, n-hexane, and CCl₄ has been investigated by infrared (IR) and polarized Raman spectroscopy. For the neat liquid of NdMA, the noncoincidence of the aniso- and isotropic Raman wavenumbers is evident. In the 0.47 M cyclohexane solution of NdMA, the noncoincidence effect almost disappears and the ν_CO envelopes in both the Raman and IR spectra are asymmetric to the low-wavenumber side. When the concentration of NdMA decreases from 0.33 to 0.023 M, the peak of these bands slightly shifts to a higher wavenumber and the band shape becomes symmetric. The shape of the ν_CO envelope does not show any significant change below 0.023 M. These results suggest that the asymmetric shape of the ν_CO band observed for the 0.33 M cyclohexane solution is associated with the intermolecular interaction among NdMA molecules, which vanishes at around 0.02 M. Spectral changes for the CCl₄ solution of NdMA show a similar tendency. However, the shape and peak wavenumber of the ν_CO band observed in a highly diluted CCl₄ solution (≤0.023 M) indicate that the solvation effect of CCl₄ is more complicated than those of cyclohexane and n-hexane. The analyses of the ν_CO band, which is sensitive to the intermolecular interaction between solutes and between solute and solvent for NdMA dissolved in nonpolar solvents, would serve to clarify the electronic property of the molecule in a solution.     

Gas phase reaction of heptafluoroisopropyl radicals with carbon tetrachloride

The reaction was investigated in the gas phase over the range 80–225°C using the photolysis of heptafluoroisopropyl iodide as the source of radicals. The rate constant, based on the value of 10^13.36 cm³ mol^?1 s^?1 for the recombination of i-C₃F₇ radicals, is given by where θ = 2.303 RT/cal mol^?1. Arrhenius parameters for chlorine abstraction from CCl₄ by CF₃, C₂F₅, n-C₃F₇, and some hydrogenated radicals are compared.     

The kinetics and the mechanism of the thermal gas-phase reaction between NO2 and 1,1-dichlorodifluoroethylene,CF2CCl2

The kinetics of the gas phase reaction between NO₂ and CF₂CCl₂ has been investigated in the temperature range from 50 to 80°C. The reaction is homogeneous. Three products are formed: O₂NCF₂CCl₂NO₂ and equimolecular amounts of CINO and of O₂NCF₂C(O)Cl. The rate of consumption of the reactants is independent of the total pressure, the reaction products, and added inert gases and can be represented by a second-order reaction: However, the distribution of the products is influenced by the pressure of the present gases, which favor the formation of the dinitro-compound in a specific way. The effect of CF₂CCl₂ is the greatest. In the absence of added gases, the ratio of O₂NCF₂CCl₂NO₂ to that of O₂NCF₂C(O)Cl is proportional to (CF₂CCl₂ + γ_P products). The experimental results can be explaned by the following mechanism: P and X represent the products and the added gases:      

Improvement of Fluorescence Lifetime from Er-Doped Sol-Gel Silica Glass by Dehydration in CCl4

Monolithic Er-doped silica xerogels with erbium content of 5000 ppm were prepared by sol-gel technique. Samples were densified by thermal treatment in O₂/CCl₄ environment. The 1.55 m photoluminescence lifetimes after annealing at different temperatures were measured, together with the relative content of hydroxyl groups inside the samples. It was found that hydroxyl groups can be removed by CCl₄ effectively. Consequently the photoluminescence lifetime of the samples increased significantly after the removal of hydroxyl groups. For sample treated in O₂/CCl₄ at 900°C, fluorescence lifetime as long as 6ms was obtained and is pretty stable when the sample is kept in ambient air.     

Synthesis of heterocycles on the basis of products of addition of polyhaloalkanes to unsaturated systems.

Oximes of 3,3-dichloropropenal and 4,4,4-trifluoro-3-chloro-1-butenal were obtained on the basis of products of free-radical addition of CCl₄ and CF₃CCl₃ to vinyl butyl ether. Generation of the corresponding nitrile oxides from these oximes and reaction of the nitrile oxides in situ with vinyl butyl ether, phenylacetylene, and propargyl alcohol via the scheme of 1,3-dipolar cycloaddition are proposed as a method for the synthesis of isoxazoles containing ,-dichlorovinyl and -trifluoromethyl--chlorovinyl substituents in the 3 position.See [1] for Communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1250–1255, September, 1990.     

The reaction of cyclohexyl radicals with carbon tetrachloride

The photolysis of azocyclohexane, carbon tetrachloride, and cyclohexane at 360 nm has been investigated over a wide temperature range. At moderate temperatures a chain reaction ensues from which the following approximate rate constants could be determined assuming 2CCl₃. → C₂Cl₆, k₅ = 10^9.7 (303–673K): The really striking feature of the results is that they show that termination in bicyclohexyl [reaction (7)] is extremely slow: The root-mean-square rule for estimating the cross-combination rate is also followed. The photolysis of carbon tetrachloride and cyclohexane at 250 nm has also been investigated. The reaction is complicated by the occurrence of two concurrent photolytic processes, the main one yielding trichloromethyl radicals and chlorine atoms, and the subsidiary one yielding dichlorocarbene and molecular chlorine. Nonetheless the results from this reaction can be interpreted in the medium temperature range 360–430K, where long chains are present, in terms of the rate constants derived from the azocyclohexane system.