Reaction Of CCl4 Research Articles

Tuning catalytic activity of dimolybdenum paddlewheel complexes by ligands: mechanism study on the radical addition reaction of CCl4 to 1-hexene

The detailed catalytic mechanism of a series of paddlewheel complexes [Mo2L4] featuring Mo-Mo quadruply-bond on radical addition of CCl4 to 1-hexene was studied using density functional theory. Different ligands of Mo-Mo bond are investigated to illustrate the ligand effect on the catalytic activity. The results show that the Mo-Mo quadruply-bond paddlewheel complexes have high catalytic activities on the title reaction. The whole reaction involves 4 steps. Firstly, the C-Cl bond of first CCl4 is activated by [Mo2L4] catalyst, and [Mo2L3Cl] and CH3COOCCl3 are obtained. Then the second CCl4 adds to [Mo2L3Cl] to produce [Mo2L3Cl2] and·CCl3 radical;·CCl3 radical interacts with 1-hexene to get an addition, the addition product which reacts with one Cl atom of [Mo2L3Cl2] to get the last product nBuCHClCH2CCl3 and regenerate [Mo2L3Cl]. The addition of the first CCl4 to [Mo2L4] catalyst is the rate-determining step of the whole reaction. Because this step is not in the catalytic cycle, the reaction would speed up after a certain period of time. The catalytic activity of dimolybdenum paddlewheel complex is depended on the natural population analysis (NPA) charge of Mo and the redox potential E(Mo24+/Mo25+). The higher NPA of Mo atom and higher E(Mo24+/Mo25+) of the catalyst, the higher catalytic activity it has. Our results provide an explanation for experimental observations and useful insights for further development of bimetallic catalysts in radical addition reactions.

Reaction of Mass-Selected, Thermalized V nO m+ Clusters with CCl4.

The kinetics of V nO m+ + CCl4 ( n, m = 2, 5; 3, 6-8; 4, 9-11; 5, 12-13) have been measured under thermal conditions using a selected-ion flow tube equipped with a laser vaporization ion source. All reactions proceed at approximately the capture rate limit, yielding three dominant categories of products: CCl3+ + V nO mCl (i.e., chloride transfer), COCl2 (phosgene) formation, and CO2 formation. Both CO2 and COCl2 are products of CCl4 reaction on a bulk vanadium oxide surface, while chloride (or chlorine) transfer is not observed. The product branching fraction of CCl3+ approaches 100% for small (V2) reactants and generally decreases with increasing cluster size down to <5% for V5O13. The fraction of chloride transfer is correlated to the fraction of terminal oxygen atoms in the V nO m+ reactant. As cluster size increases, phosgene replaces chloride transfer as the dominant product channel. The channel producing CO2 is observed only for highly oxygenated clusters, V3O8+, V4O11+, and V5O13+, and appears to require a superoxide O2 in the reactant structure; the mechanism is likely distinct from that producing CO2 on bulk V2O5. Increasing the temperature of the system from 300 to 500 K increases the observed fraction of CCl3+ at the expense of all other product channels. Likely mechanisms, informed by density functional calculations, are discussed.

Preparation and Properties of Chlorosulfuryl Chloroformate, ClC(O)OSO2Cl.

The novel chlorosulfuryl chloroformate, ClC(O)OSO2Cl, was prepared by the reaction of CCl4 and SO3. Alternatively, the compound was obtained from the direct insertion reaction of SO3 to Cl2C═O. The latter reaction constitutes also a confirmation of the proposed mechanism for the former one. Density functional theory and MP2 theoretical approximations predict the existence of two conformers, syn-gauche and syn-anti, depending on the value adopted by the dihedral angles ϕ(Cl-C-O-S) and ϕ(C-O-S-Cl). The structure of the syn-gauche conformer was determined by gas-phase electron diffraction (GED). The existence of the syn-anti conformer can be neither confirmed nor excluded by the GED experiment. Vibrational spectra (vapor-phase and argon-matrix Fourier transform infrared and liquid Fourier transform Raman) were interpreted by an equilibrium mixture between both conformers.

Structural and Electronic Noninnocence of α-Diimine Ligands on Niobium for Reductive C–Cl Bond Activation and Catalytic Radical Addition Reactions

A d0 niobium(V) complex, NbCl3(α-diimine) (1a), supported by a dianionic redox-active N,N'-bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1,3-butadiene (α-diimine) ligand (ene-diamido ligand) served as a catalyst for radical addition reactions of CCl4 to α-olefins and cyclic alkenes, selectively affording 1:1 radical addition products in a regioselective manner. During the catalytic reaction, the α-diimine ligand smoothly released and stored an electron to control the oxidation state of the niobium center by changing between an η4-(σ2,π) coordination mode with a folded MN2C2 metallacycle and a κ2-(N,N') coordination mode with a planar MN2C2 metallacycle. Kinetic studies of the catalytic reaction elucidated the reaction order in the catalytic cycle: the radical addition reaction rate obeyed first-order kinetics that were dependent on the concentrations of the catalyst, styrene, and CCl4, while a saturation effect was observed at a high CCl4 concentration. In the presence of excess amounts of styrene, styrene coordinated in an η2-olefinic manner to the niobium center to decrease the reaction rate. No observation of oligomers or polymers of styrene and high stereoselectivity for the radical addition reaction of CCl4 to cyclopentene suggested that the C-C bond formation proceeded inside the coordination sphere of niobium, which was in good accordance with the negative entropy value of the radical addition reaction. Furthermore, reaction of 1a with (bromomethyl)cyclopropane confirmed that both the C-Br bond activation and formation proceeded on the α-diimine-coordinated niobium center during transformation of the cyclopropylmethyl radical to a homoallyl radical. With regard to the reaction mechanism, we detected and isolated NbCl4(α-diimine) (6a) as a transient one-electron oxidized species of 1a during reductive cleavage of the C-X bonds; in addition, the monoanionic α-diimine ligand of 6a adopted a monoanionic canonical form with selective one-electron oxidation of the dianionic ene-diamido form of the ligand in 1a.

Direct Solvothermal Synthesis of B/N‐Doped Graphene

AbstractHeteroatom‐doping into graphitic networks has been utilized for opening the band gap of graphene. However, boron‐doping into the graphitic framework is extremely limited, whereas nitrogen‐doping is relatively feasible. Herein, boron/nitrogen co‐doped graphene (BCN‐graphene) is directly synthesized from the reaction of CCl4, BBr3, and N2 in the presence of potassium. The resultant BCN‐graphene has boron and nitrogen contents of 2.38 and 2.66 atom %, respectively, and displays good dispersion stability in N‐methyl‐2‐pyrrolidone, allowing for solution casting fabrication of a field‐effect transistor. The device displays an on/off ratio of 10.7 with an optical band gap of 3.3 eV. Considering the scalability of the production method and the benefits of solution processability, BCN‐graphene has high potential for many practical applications.

Direct Solvothermal Synthesis of B/N‐Doped Graphene

Heteroatom-doping into graphitic networks has been utilized for opening the band gap of graphene. However, boron-doping into the graphitic framework is extremely limited, whereas nitrogen-doping is relatively feasible. Herein, boron/nitrogen co-doped graphene (BCN-graphene) is directly synthesized from the reaction of CCl4 , BBr3 , and N2 in the presence of potassium. The resultant BCN-graphene has boron and nitrogen contents of 2.38 and 2.66 atom %, respectively, and displays good dispersion stability in N-methyl-2-pyrrolidone, allowing for solution casting fabrication of a field-effect transistor. The device displays an on/off ratio of 10.7 with an optical band gap of 3.3 eV. Considering the scalability of the production method and the benefits of solution processability, BCN-graphene has high potential for many practical applications.

High-pressure-activated carbon tetrachloride decomposition

The pressure-induced molecular dissociation as one of the fundamental problems in physical sciences has aroused many theoretical and experimental studies. Here, using a newly developed particle swarm optimization algorithm, we investigate the high-pressure-induced molecular dissociation. The results show that the carbon tetrachloride (CCl4) is unstable and dissociates into C2Cl6 and Cl2 under approximately 120 GPa and more. The dissociation is confirmed by the lattice dynamic calculations and electronic structure of the Pa3 structure with pressure evolution. The dissociation pressure is far larger than that in the case of high temperature, indicating that the temperature effectively reduces the activation barrier of the dissociation reaction of CCl4. This research improves the understanding of the dissociation reactions of CCl4 and other halogen compounds under high pressures.

Degradation of sulfadiazine antibiotics by water falling film dielectric barrier discharge

Abstract A new water falling film dielectric barrier discharge was applied to the degradation of sulfadiazine in the aqueous solution. The various parameters that affect the degradation of sulfadiazine and the proposed evolutionary process were investigated. The results indicated that the inner concentrations of 10 mg/L sulfadiazine can be all removed within 30 min. The optimum pH value was 9.10 and both strong acidic and alkaline solution conditions were not suitable for the degradation. The degradation of sulfadiazine can be enhanced by the addition of hydrogen radical scavengers, but be inhibited by adding hydroxyl radical scavengers. The water falling film dielectric barrier discharge was rather ineffective in mineralization, because of the intermediates were recalcitrant to be degraded. The existence of Fe2+ and CCl4 in the liquid phase can promote the degradation and mineralization of sulfadiazine. It was found that the degradation of SDZ was enhanced by CCl4 was mainly because of the increase of OH due to the reaction of CCl4 with H that reduce the chances of their recombination with OH. Based on the 8 intermediate products identified by LC–MS, the proposed evolution of the degradation process was investigated.

Water assisted reaction mechanism of OH− with CCl4 in aqueous solution – Hybrid quantum mechanical and molecular mechanics investigation

The OH−(H2O)+CCl4 reaction in aqueous solution was investigated using the combined quantum mechanical and molecular mechanics approach. The reaction mechanism of OH−(H2O)+CCl4 consists of two concerted steps – formation of OH− in the favorable attack conformation via the proton transfer process, and the nucleophilic substitution process in which the newly formed OH− attacks the CCl4. The free energy activation barrier is 38.2kcal/mol at CCSD(T)/MM level of theory for this reaction, which is about 10.3kcal/mol higher than that of the direct nucleophilic substitution mechanism of the OH−+CCl4 reaction in aqueous solution.

Hydrodechlorination Reactions of CCl4 Over HZSM-5- and HY-Supported Pt and Pd Catalysts

The hydrodechlorination reactions of CCl4 have been studied over Pt/HZSM-5, Pt/HY, Pd/HZSM-5 and Pd/HY under hydrogen atmosphere in the 393–673 K temperature range in a pulse microreactor. The catalysts were prepared by impregnation and were characterised by various physico-chemical means. It has been found that all catalysts were active in the partial to full dechlorination reactions. Typically, over the Pt-containing catalysts methane was the major dechlorinated product, while it was ethane over the Pd-containing catalysts. This latter product predominated over the Pd/HZSM-5 and the quantities of the di- and trichlorinated products were minimal and the monochlorinated one was not formed at all. Phosgene formed was the indication of the partial destruction of the support being more serious for the HY-supported ones.

Hybrid Quantum Mechanical and Molecular Mechanics Study of the SN2 Reaction of CCl4 + OH– in Aqueous Solution: The Potential of Mean Force, Reaction Energetics, and Rate Constants

The bimolecular nucleophilic substitution reaction of CCl(4) and OH(-) in aqueous solution was investigated on the basis of a combined quantum mechanical and molecular mechanics method. A multilayered representation approach is employed to achieve high accuracy results at the CCSD(T) level of theory. The potential of mean force calculations at the DFT level and CCSD(T) level of theory yield reaction barrier heights of 22.7 and 27.9 kcal/mol, respectively. Both the solvation effects and the solvent-induced polarization effect have significant contributions to the reaction energetics, for example, the solvation effect raises the saddle point by 10.6 kcal/mol. The calculated rate constant coefficient is 8.6 × 10(-28) cm(3) molecule(-1) s(-1) at the standard state condition, which is about 17 orders magnitude smaller than that in the gas phase. Among the four chloromethanes (CH(3)Cl, CH(2)Cl(2), CHCl(3), and CCl(4)), CCl(4) has the lowest free energy activation barrier for the reaction with OH(-) in aqueous solution, confirming the trend that substitution of Cl by H in chloromethanes diminishes the reactivity.

Kinetic and mechanistic studies of the reactions of diarylgermylenes and tetraaryldigermenes with carbon tetrachloride

The mechanisms of the reactions of diphenylgermylene (GePh2) with CCl4 in hydrocarbon solvents and in THF solution have been studied, employing 3,4-dimethyl-1,1-diphenylgermacyclopent-3-ene (6a) and 1,1-diphenylgermacyclobutane (17) as photochemical precursors to GePh2. In hydrocarbon solvents, the reaction produces Ph2GeCl2 (10) and Ph2Ge(Cl)CCl3 (12) in a ratio of 10:12 ≈ 7, along with a variety of other radical-derived products and small amounts of Ph2GeH(D)Cl (11), which is formed partly by reaction of GePh2 with adventitious HCl. The reaction is much cleaner in THF, where 12 is formed as the major product (10:12 ≈ 0.8); a similar product distribution is obtained in hexanes containing 0.05 mol/L THF, while 12 is the exclusive product in hexanes containing 3 mmol/L NEt3. Rate constants for the reactions of CCl4 with GePh2 and five ring-substituted derivatives were determined by laser flash photolysis, as well as Arrhenius parameters for reaction of the parent (GePh2), in the two solvents. The reactions of GePh2 with CCl4 and CHCl3 have also been studied in 3-methylpentane solution at 78–90 K. Different reaction mechanisms are clearly operative in hydrocarbon and complexing solvents, but both involve modest charge donation from germanium to the substrate in the transition state for the rate-determining step. For the reaction in hydrocarbon solvents, the data are consistent with inner-sphere electron transfer following or in concert with weak Lewis acid–base complexation. A similar mechanism is proposed for the reaction in THF solution, in competition with a second involving nucleophilic attack of the germylene–THF complex at a chlorine atom of the substrate. Rate constants were also determined for reaction of CCl4 with the corresponding tetraaryldigermenes at low halocarbon concentrations in hexanes, along with Arrhenius parameters for the parent (Ge2Ph4). These reactions also proceed via initial Cl-atom abstraction, based on the identity of the products formed in the reaction of CCl4 with tetramesityldigermene.

Kinetics and dynamics study of the H + CCl4 → HCl(v′, j′) + CCl3 reaction

Based on a previous potential energy surface describing the H + CCl4 reaction, a new analytical surface named PES-2010 was developed modifying both the functional form to give it more flexibility, and the calibration process in which exclusively theoretical information was used. Thus, the surface is completely symmetric with respect to the permutation of the four methane chlorine atoms, and no experimental information is used in the process. For the kinetics, the thermal rate constants were calculated using variational transition-state theory with semiclassical transmission coefficients over a wide temperature range, 300–2,500 K. The theoretical results reproduce the experimental variation with temperature. The influence of the tunneling factor is small, since the abstraction reaction involves the motion of a heavy particle (a chlorine atom) that cannot easily tunnel through the reaction barrier. The coupling between the reaction coordinate and the vibrational modes shows qualitatively that the HCl stretching mode in the products appears vibrationally excited. The dynamics study was performed using quasi-classical trajectory calculations, including corrections to avoid the zero-point energy problem. First, we found that the HCl(ν′, j′) product mostly appears with small rotational energy and vibrational population inversion. Second, the state-specific scattering distributions show backward scattering, which becomes more noticeable as the HCl(ν′) vibrational state increases. Unfortunately, no experimental dynamics data are available for the title reaction, but the comparison with the kinematically similar and well-studied H + Cl2 reaction shows good agreement, indicative of similar mechanisms. These kinetics and dynamics results seem to indicate that the potential energy surface is adequate to describe this reaction, and the reasonable agreement with experiment lends further confidence to this new surface.

Mechanism of the formation of carbon oxides under conditions of the oxidative chlorination of methane: III. Kinetics of the reaction of CCl4 with oxygen on copper-containing salt catalysts

The kinetics of the oxidative dechlorination of CCl4 on two supported catalysts for methane oxychlorination (CuCl2-KCl and CuCl2-KCl-LaCl3) at 350–425°C was studied using a gradientless method. Although these catalysts exhibited different activities, the rate of reaction on them was described by one exponential equation at the same activation energy of E ≈ 26.3 kcal/mol. A two-path reaction mechanism was proposed, which involved the dissociative adsorption of initial reactants and chlorine with the formation of phosgene and the oxidation of phosgene to CO2. The occurrence of two types of active sites on the catalyst surface was assumed.

Mechanism of the formation of carbon oxides under conditions of the oxidative chlorination of methane: IV. Kinetics of the reaction of CCl4 with oxygen on copper-containing salt catalysts for methane oxychlorination at reduced partial pressures of Cl2 in the reaction mixture

The kinetics of the oxidative dechlorination of CCl4 on two supported salt catalysts for methane oxychlorination (CuCl2-KCl and CuCl2-KCl-LaCl3) in the presence of methane at 350–450°C was studied using a gradientless method. It was found that, at \( P_{Cl_2 } \) > 0.15 kPa, the presence of methane in the reaction mixture had no effect on the kinetics of CCl4 oxidation but decreased the activation energy E to ∼22 kcal/mol. At \( P_{Cl_2 } \) < 0.15 kPa, the kinetic orders with respect to oxygen and chlorine changed and E decreased to ∼17 kcal/mol. The rate of formation of CO2 as a by-product of the reaction of methane oxychlorination was described by an exponential equation in combination with rate equations for the oxidation of other chloromethanes and methane. An equation consistent with the observed rate laws of this reaction in the presence of methane was derived from the previously proposed reaction scheme for the mechanism of the oxidative dechlorination of CCl4.

Dinuclear Ruthenium Ethylene Complexes: Syntheses, Structures, and Catalytic Applications in ATRA and ATRC Reactions

The complexes [(p-cymene)Ru(μ-Cl)3RuCl(C2H4)(PR3)] (PR3 = PPh3, Pn-Bu3) were synthesized by reaction of [(p-cymene)RuCl(μ-Cl)]2 with the respective phosphine ligand in the presence of ethylene. Structurally related complexes containing the tricyclopentylphosphine (PCyp3) or the isobutylphobane ligand (phobane = 9-phosphabicyclo[3.3.1]nonane) were obtained by reaction of [(arene)RuCl(μ-Cl)]2 (arene = p-cymene, 1,3,5-i-Pr3C6H3) with 2 equiv of [(arene)RuCl2(PCyp3)] or [(arene)RuCl2(isobutylphobane)] in the presence of ethylene. The structures of the dinuclear complexes [(p-cymene)Ru(μ-Cl)3RuCl(C2H4)(PPh3)] and [(1,3,5-i-Pr3C6H3)Ru(μ-Cl)3RuCl(C2H4)(isobutylphobane)] as well as of the mononuclear precursors [(p-cymene)RuCl2(isobutylphobane)], [(1,3,5-i-Pr3C6H3)RuCl2(isobutylphobane)], and [(p-cymene)RuCl2(PCyp3)] were determined by single-crystal X-ray analyses. Kinetic analyses of the atom transfer radical addition reaction of CCl4 to styrene revealed that the catalytic activity of the dinuclear complexes was strongly dependent on the nature of the phosphine ligand but only slightly affected by the nature of the arene ligand. Addition of Mg to the reaction mixture was found to increase the lifetime of the catalyst significantly. With Mg as the cocatalyst, mixed-valence Ru(II)−Ru(III) complexes of the general formula [(arene)Ru(μ-Cl)3RuCl2(PR3)] were found to be equally potent catalyst precursors when compared to the Ru(II)−Ru(II) complexes [(arene)Ru(μ-Cl)3RuCl(C2H4)(PR3)].

Response to “Comment on ‘Resonant dissociative electron transfer of the presolvated electron to CCl4 in liquid: Direct observation and lifetime of the CCl4∗− transition state’ [J. Chem. Phys. 129, 027101 (2008)

In our recent paper [J. Chem. Phys.128, 041102 (2008)], we reported a femtosecond time-resolved laser spectroscopic study of the electron transfer reaction of CCl4 in liquid ethanol. Our results provide direct evidence of the resonant dissociative electron transfer (RDET) of the presolvated electron to CCl4, and indicate that RDET can be an efficient process in an aqueous environment. In a recent Comment, the author argues that the relevance of diethanolamine (DEA) induced destruction of chlorofluorocarbons (CFCs) in the polar stratosphere as a possible pathway for chemical ozone destruction should not be a motivation for further studies of DEA on CFC molecules, as no correlation is observed between polar chemical ozone loss and cosmic ray activity. Here, we show that this claim is misleading: it is made by using inconclusive and ambiguous data while ignoring pronounced and well-documented data.

Resonant dissociative electron transfer of the presolvated electron to CCl4 in liquid: Direct observation and lifetime of the CCl4*− transition state

We report a pump-probe femtosecond transient absorption spectroscopic study on the electron transfer reaction of CCl(4) in liquid ethanol. By direct observations of the presolvated electron and of the reaction transition state CCl(4) (*-), this study provides direct evidence of the resonant dissociative electron transfer (RDET) of the presolvated electron to CCl(4). Moreover, the lifetime of CCl(4) (*-) in ethanol is directly obtained from the decay kinetics and its measured value is found to be nearly identical to its gas-phase value. Hence, these results also imply that RDET can be an efficient process in an aqueous environment.

2,6-Bis(oxazolinyl)phenylnickel(II) Bromide and 2,6-Bis(ketimine)phenylnickel(II) Bromide: Synthesis, Structural Features, and Redox Properties

2,6-Bis(oxazolinyl)phenylnickel bromide complexes [NiBr(R,R‘-Phebox)] (2) were synthesized via two synthetic routes (A and B). In route A, selective bis-ortho lithiation of [R,R‘-PheboxBr], followed by a transmetalation reaction with [NiBr2(PEt3)2], yielded not only complexes 2 with an η3-mer-N,C,N‘-bonded Phebox ligand but also [NiBr(R,R‘-Phebox)(PEt3)2], 7, where the nickel center is η1-C bonded to the intra-annular Cipso of the Phebox ligand. Coordination of two PEt3 ligands completes the square-planar coordination sphere of the Ni center in 7. When R = t-Bu, R‘ = H, only complex 7c was formed. Alternatively, when route B (oxidative addition with [Ni(cod)2], cod = cyclooctadiene) was followed, selective formation of complexes 2 was observed. X-ray crystal structures were obtained for [NiBr-(i-Pr,H-Phebox)] (2b) and [NiBr(bis(ketimine)phenyl)] (3). The Ni centers have square-planar geometries with a planar, η3-mer-N,C,N‘ coordination of the terdentate ligand systems. Complexes 2 were found to be inactive as catalysts in the atom-transfer radical polymerization (ATRP) reaction of methyl methacrylate (MMA) and in the atom-transfer radical addition (ATRA, Kharasch addition) reaction of CCl4 to MMA. This is ascribed to the relatively high oxidation potential of NiII−Phebox complexes, which excludes the (reversible) formation of a d7-NiIII−Phebox complex, a crucial condition for subsequent reactions. Cyclovoltammetry (CV) experiments ((n-Bu)4NBr as supporting electrolyte) showed no electrochemical waves between −1.00 and +1.50 V (Ag/AgCl reference electrode, (n-Bu)4NBr as supporting electrode). Theoretical calculations showed that the energy (Eox) needed for the oxidation reaction occurring during the CV experiments is considerably higher for [NiBr(Me,Me-Phebox)] (1.87 eV) and [NiBr(bis(ketimine)phenyl)] (1.90 eV) than for [NiBr(NCN)] (1) (1.45 eV).

Hydrodechlorination over Pd–Pt/Al2O3 catalysts: A comparative study of chlorine removal from dichlorodifluoromethane, carbon tetrachloride and 1,2-dichloroethane

A comparative study of hydrodechlorination of dichlorodifluoromethane, carbon tetrachloride and 1,2-dichloroethane over alumina-supported Pd–Pt catalysts showed several interesting features in the catalytic behavior. Platinum, the metal which binds chlorine and chlorine-containing organic intermediate species less strongly than palladium is a better catalyst in CCl4 hydrodechlorination. However, in hydrodechlorinations of CCl2F2 and 1,2-dichloroethane platinum offers too weak binding with reaction species, and in effect, Pd/Al2O3 shows a better catalytic performance than Pt/Al2O3. Nevertheless, this positive behavior of Pd/Al2O3 can still be improved by doping it with small amounts of platinum. The formation of mixed Pd–Pt ensembles leads to an enhancement of the overall activity and selectivity for partial hydrodehalogenation. Temperature-programmed hydrogenation (TPH) of deposits accumulated on the catalysts during hydrodechlorination confirms a better resistance of platinum against carbiding. In the case of Pd/Al2O3 and Pd–Pt/Al2O3 catalysts, massive amounts of coke (and chlorine) were found after CCl4 reaction.