鬼臼毒素及其衍生物热分解反应的动力学研究

The thermal behavior and thermal decomposition kinetic parameters of podophyllotoxin （1） and 4 derivatives, picropodophyllin （2）, deoxypodophyllotoxin （3）, fl-apopicropodophyllin （4）, podophyllotoxone （5） in a temperature-programmed mode have been investigated by means of DSC and TG-DTG. The kinetic model functions in differential and integral forms of the thermal decomposition reactions mentioned above for first stage were established. The kinetic parameters of the apparent activation energy Ea and per-exponential factor A were obtained from analy- sis of the TG-DTG curves by integral and differential methods. The most probable kinetic model function of the decomposition reaction in differential form was （1- a）^2 for compounds 1-3,2/3·a^-1/2 for compound 4 and 1/2（1-a）·[-In（1-a）]^-1 for compound 5. The values of Ea indicated that the reactivity of compounds 1-5was increased in the order： 5〈4〈2〈1〈3. The values of the entropy of activation △S^≠, enthalpy of activation △H^≠ and free energy of activation △G^≠ of the reactions were estimated. The values of △G^≠ indicated that the thermal stability of compounds 1-3 with the samef（a） was increased in the order： 2〈3〈1.     

Synthesis and Thermal Behavior of 1,8-Dihydroxy- 4,5-dinitroanthraquinone Manganese Salt

A novel energetic combustion catalyst, 1,8-dihydroxy-4,5-dinitroanthraquinone manganese salt （DHDNEMn）, was synthesized by virtue of the metathesis reaction in a yield of 91%, and its structure was characterized by IR, element analysis and differential scanning calorimetry（DSC）. The thermal decomposition reaction kinetics was studied by means of different heating rate DSC. The results show that the apparent activation energy and pre-exponential factor of the exothermic decomposition reaction of DHDNEMn obtained by Kissinger＇s method are 162.3 kJ/mol and 1011.8 s^-1, respectively. The kinetic equation of major exothermic decomposition reaction of DHDNEMn is dα/dT= 10^118/β 2/5（1-α）[-ln（1-α）[-ln（1-α）]^3/5 exp（-1.623×10^5/RT）. The entropy of activation（△S^≠）, enthalpy of activation（△H^≠） and free energy of activation（A△G^≠） of the first thermal decomposition are -24.49 J·mol^-1·K^-1, 185.20 kJ/mol and 199.29 kJ/mol（T=575.5 K）, respectively. The self-accelerating decomposition temperature（TSADT） and critical temperature of thermal explosion（Tb） are 562.9 and 580.0 K, respectively. The above-mentioned information on the thermal behavior is quite useful for analyzing and evaluating the stability and thermal safety of DHDNEMn.     

Thermal Kinetics and Decomposition Mechanism of 1-Amino-1,2,3-triazolium Nitrate

The thermal decomposition kinetics of 1-amino-l,2,3-triazolium nitrate（ATZ-NO3） was investigated by non-isothermal TG-DTG at various heating rates（2,5,10,15 and 20 ℃/min）.The results show that the thermal decomposition of ATZ-NO3 consists of two stages corresponding to the losing of nitrate anion,substituent group and the splitting of triazole ring respectively.The kinetic triplets of the two stages were described by a three-step method.First,the differential Kissinger and intergral Ozawa methods were used to calculate the apparent activation energies（E） and pre-exponential factors（A） of the two decomposition stages.Second,two calculation methods（intergral （S）atava-（S）esták and differential Achar methods） were used to obtain several probable decomposition mechanism functions.Third,three judgment methods（average,double-extrapolation and Popescu methods） were used to confirm the most probable decomposition mechanism functions.Both reaction models of the two stages were randominto-nucleation and random-growth mechanisms with n=3/2 for the first stage and n=1/3,m=3 for the second stage.The kinetic equations for the two decomposition stages of ATZ-NO3 may be expressed as da/dt=1013.60·e-128970/RT（1-α）[-1n（1-α）]-1/2 and da/dt=1011.41·e-117370/RT（1-α）[-1n（1-α）]-2/3.The thermodynamic parameters including Gibbs free energy of activation（△G≠）,entropy of activation（△S≠） and enthalpy of activation（△H≠）,for the thermal decomposition reaction were also derived.     

环丙沙星-钨硅多金属氧酸盐的制备及热分解动力学

A new polyoxometalate （CPFX·HCl）3H4SiW12O40·10H2O was prepared from ciprofloxacin hydrochloride and H4SiW12O40·nH2O in aqueous solution, and characterized by elemental analysis, IR spectra and DTA-TG-DTG techniques. The IR spectrum confirmed the presence of Keggin structure and the characteristic functional group for ciprofloxacin in the compound. The TG-DTA-DTG curves showed that its thermal decomposition was a four-step process consisting of simultaneous collapse of Keggin type structure. The residue of decomposition was the mixture of WO3 and SiO2, confirmed by X-ray diffraction and IR spectroscopy. The decomposition mechanism and nonisothermal kinetic parameters of the polyoxometalate were obtained from an analysis to the TG-DTG curves by the single scanning methods （the Achar method and Coats-Redfern method） and the multiple scanning methods （the Kissinger method, Flynn-Wall-Ozawa method and Starink method）. The results indicate that the kinetic equationswith parameters describing the thermal decomposition reaction are dα/dt=6.65×10^6[3（1-α）^2/3]e^-10495.5/T with E=87.26 kJ/mol and A=6.65×10^6 s^-1 for the second step,dα/dt=7.01×10^9（1-α）e^-18770.7/T with E=156.06 kJ/mol and A=7.01×10^9 s^-1 for the third step,dα/dt=9.77×10^43[（1-α）^2]e^-88980.0/T with E=739.78 kJ/mol and A=9.77×10^43 s^-1 for the fourth step.     

Thermal Degradation Kinetics of N,N＇-Di（diethoxythiophosphoryl）-1,4-phenylenediamine

The non-isothermal degradation kinetics of N,N＇-di（diethoxythiophosphoryl）-1,4-phenylenediamine in N2 was studied by TG-DTG techniques.The kinetic parameters,including the activation energy and pre-exponential factor of the degradation process for the title compound were calculated by means of the Kissinger and Flynn-Wall-Ozawa（FWO）method and the thermal degradation mechanism of the title compound was also studied with the Satava-Sestak methods.The results indicate that the activation energy and pre-exponential factor are 152.61 kJ/mol and 9.06×101 4s -1with the Kissinger method and 154.08 kJ/mol with the Flynn-Wall-Ozawa method,respectively.It has been shown that the degradation of the title compound follows a kinetic model of one-dimensional diffusion or parabolic law,the kinetic function is G（α）=α2and the reaction order is n=2.     

Synthesis,crystal structure and thermal behavior of 4-amino-3,5-dinitropyrazole copper salt

A novel energetic combustion catalyst, 4-amino-3,S-dinitropyrazole copper salt （[Cu（adnp）2（H2O）2]）, was synthesized in a yield of 93.6% for the first time. The single crystal of [Cu（adnp）2（H2O）2] was determined by single crystal X-ray diffraction. It crystallizes in a triclinic system, space group p^-1 with crystal parameters a = 5.541（3） A, b = 7.926（4） A, c = 10.231（5） A,β = 101.372（8）°, V = 398.3（3） A3, Z = 1, μ = 1.467 mm^-1, F（0 0 0） = 243, and Dc = 2.000 g cm^-3. The thermal behavior and non-isothermal decomposition reaction kinetics of [Cu（adnp）2（H2O）2] were studied by means of different heating rate differential scanning calorimetry （DSC）. The kinetic equation of major exothermic decomposition reaction for [Cu（adnp）2（H2O）2] was obtained. The entropy of activation （△S≠）, enthalpy of activation （△H≠）, free energy of activation （△G≠）, the self-accelerating decomposition temperature （TSADT） and the critical temperature of thermal explosion （Tb） are 59.42 j mol^-1 K^-1, 169.5 kJ mol^-1, 1141.26 kJ mol ^-1 457.3 K and 468.1 K, respectively.     

A Thermochemical Study on Complex Nickel（Ⅲ）L—α—Histidine

The formation enthalpy ofcomplex nickel(Ⅱ）-histidine(His)in water was determined by means of microcalorimetry in the temperature range of 298.15-323.15K.The standard enthalpy of the formation of Ni(His)2^2 (aq) was calculated.On the basis of the experimental and the calculated results,three thermodynamic parameters(the activation enthaly,the activation entropy and the activation free energy),the rate constants,three kinetic parameters(the apparent activation energy,the pre-exponential constant and the reaction order)of the formation reaction of the title complex were obtained.     

STUDY ON THE KINETICS OF POLYMERIZATION OF MMA BY COPPER（Ⅱ） CHELATING RESINS

The polymerization of MMA initiated by copper(Ⅱ） chelating resins/CCl4 system was studied.From the kinetic data,the kinetic equation of polymerization can be expressed as Rp=Ke^-56400/RT[MMA]^1.57[CCl4]^m[RESIN-Cu]^0.18 where m:3-4.5,when[CCl4] 0.1-6.93M.The free radical polymerization mechanism is proposed.The primary radicals are formed by the process of complexation-chlorine transformation among the copper(Ⅱ) chelating resin,CCl4 and methacrylate.     

Synthesis,Crystal Structure,and Catalytic Performance of 2,6-Bis[1-（2,4,6-trimethylphenylimino）ethyl]pyridine Nickel（II） Complex

A novel nickel（II）-complex Ni[L]Cl2-CH3CN（1） containing the tridentate ligand 2,6-bis[1-（2,4,6- trimethylphenylimino）ethyl]pyridine（L） has been synthesized. The crystal structure of complex 1 was determined by single crystal X-ray diffraction analysis. The catalytic activity of complex 1 for the polymerization of ethylene was studied under activation with methylaluminoxane（MAO）.     

Non-isothermal Decomposition Kinetics of [Cu（en）2H2O] （FOX-7）2·H2O

The thermal behavior and non-isothermal decomposition kinetics of [Cu（en）2H2O]（FOX-7）2·H2O （en=ethylenediamine） were studied with DSC and TG-DTG methods.The kinetic equation of the exothermal process is dα/dt=（10^17.92/β）4α^3/4exp（-1.688×10^5/RT）.The self-accelerating decomposition temperature and critical temperature of the thermal explosion are 163.3 and 174.8 ℃,respectively.The specific heat capacity of [Cu（en）2H2O]（FOX-7）2·H2O was determined with a micro-DSC method,with a molar heat capacity of 661.6 J·mol^-1·K^-1 at 25 ℃.Adiabatic time-to-explosion was also estimated as 23.2 s.[Cu（en）2H2O]（FOX-7）2·H2O is less sensitive.     

铀(Ⅵ)与不对称希夫碱配合物的合成和热分解反应动力学

邻苯二胺与5－氯－2－羟基二苯酮、邻香草醛作用合成了一种不对称希夫碱配体C₂₇H₂₁N₂O₃Cl（H₂L）。在正丁醇和甲醇体系中硝酸铀酰与该配体反应合成了一种固体希夫碱配合物[UO₂(HL)(NO₃)(H₂O)]·H₂O。通过元素分析、IR、UV、¹H NMR、TG-DTG及摩尔电导率分析等手段对合成的配合物进行了表征,用非等温热重法研究了铀(Ⅵ)配合物的热分解反应动力学,推断出第三步热分解的动力学方程为：d α /d t = A · e^{- E/RT} ·3/2[(1- α )^-1/3-1]^-1,得到了动力学参数E和A。并计算出了活化熵△S^¹和活化吉布斯自由能△G^¹。     

Synthesis and thermal decomposition kinetics of Er(III) complex with unsymmetrical Schiff-base ligand

A new unsymmetrical, solid, Schiff base (H₂LLi) was synthesized using L-lysine, o-vanillin and salicylaldehyde. An Er(III) complex of this ligand [Er(H₂L)(NO₃)](NO₃)?·?2H₂O was prepared and characterized by elemental analysis, IR, UV and molar conductance. The thermal decomposition kinetics of the complex for the second stage was studied under non-isothermal conditions by TG and DTG methods. The kinetic equation may be expressed as, dα/dt?=?A?·?e^?E/RT ?·?1/2(1???α)[?ln(1???α)]^?1. The kinetic parameters (E,?A), activation entropy S ^≠ and activation free-energy G ^≠ were also determined.     

Experimental and Computational Mechanistic Studies of the β-Diketiminatoiron(II)-Catalysed Hydroamination of Primary Aminoalkenes

A comprehensive mechanistic study by means of complementary experimental and computational approaches of the exo-cyclohydroamination of primary aminoalkenes mediated by the recently reported β-diketiminatoiron(II) complex B is presented. Kinetic analysis of the cyclisation of 2,2-diphenylpent-4-en-1-amine ( 1 a ) catalysed by B revealed a first-order dependence of the rate on both aminoalkene and catalyst concentrations and a primary kinetic isotope effect (KIE) (k_H/k_D) of 2.7 (90 °C). Eyring analysis afforded ΔH^≠=22.2 kcal mol⁻¹, ΔS^≠=−13.4 cal mol⁻¹ K⁻¹. Plausible mechanistic pathways for competitive avenues of direct intramolecular hydroamination and oxidative amination have been scrutinised computationally. A kinetically challenging proton-assisted concerted N−C/C−H bond-forming non-insertive pathway is seen not to be accessible in the presence of a distinctly faster σ-insertive pathway. This operative pathway involves 1) rapid and reversible syn-migratory 1,2-insertion of the alkene into the Fe−N_amido σ bond at the monomer {N^N}Fe^II amido compound; 2) turnover-limiting Fe−C σ bond aminolysis at the thus generated transient {N^N}Fe^II alkyl intermediate and 3) regeneration of the catalytically competent {N^N}Fe^II amido complex, which favours its dimer, likely representing the catalyst resting state, through rapid cycloamine displacement by substrate. The collectively derived mechanistic picture is consonant with all empirical data obtained from stoichiometric, catalytic and kinetics experiments.     

Synthesis and thermal decomposition kinetics of Th(IV) complex with unsymmetrical Schiff base ligand

Summary A new unsymmetrical Schiff base ligand (H₂LLi) was synthesized using L-lysine, o-vanillin and salicylaladyde. Thorium(IV) complex of this ligand [Th(H₂L)(NO₃)](NO₃)₂^.3H₂O have been prepared and characterized by elemental analyses, IR, UV and molar conductance. The thermal decomposition kinetics of the complex for the second stage was studied under non-isothermal condition by TG and DTG methods. The kinetic equation may be expressed as: dα/dt=A^.e^-E/RT.1/2 (1-α)^.[-ln(1-α)]^-1. The kinetic parameters (E, A), activation entropy ΔS¹and activation free-energy ΔG¹were also calculated.     

A kinetic investigation of reaction of [Os(N)(CH2SiMe3)4][NBun4] with methyl iodide

A high oxidation state alkylnitridoosmium complex, [Os(N)(CH₂SiMe₃)₄][NBuⁿ₄] acts as a nucleophile in reactions with alkyl halides. Alkylimido complexes, Os(NR)(CH₂SiMe₃)₄, are produced. The reaction between [Os(N)(CH₂SiMe₃)₄]⁻ [NBuⁿ₄] and MeI is second order with k₂= 9.5 x 10⁻⁵ sec^t̄1 M⁻¹ at 23°C in CD₂Cl₂ under pseudo first order conditions. The entropy of activation, ΔS^≠, was found to be −10.6 ± 0.5 cal M⁻¹ K⁻¹ and the enthalpy of activation, ΔH^≠, was found to be 19.6 ± 0.2 kcal M⁻¹. The reaction proceeds faster in polar, non-coordinating solvents than in either non-polar solvents or in solvents which can coordinate to the osmium center.     

The catalytic reduction of nitrobenzene at the [MoVIO2(O2CC(S)(C6H5)2)2]2− complex intercalated in a Zn(II)–Al(III) layered double hydroxide host: A kinetic model for the molybdenum–pterin binding site in nitrate reductase

The heterogeneous reduction of nitrobenzene by thiophenol catalyzed by the dianionic bis(2‐sulfanyl‐2,2‐diphenylethanoxycarbonyl) dioxomolybdate(VI) complex, [Mo^VIO₂(O₂CC(S)(C₆H₅)₂)₂]²⁻, intercalated into a Zn(II)–Al(III) layered double hydroxide host [Zn_3−xAl_x(OH)₆]^x+, has been investigated under anaerobic conditions. Aniline was found to be the only product formed through a reaction consuming six moles of thiophenol for each mol of aniline produced. The kinetics of the system have been analyzed in detail. In excess of thiophenol, all reactions follow first‐order kinetics (ln([PhNO₂]/[PhNO₂]₀) = −k_appt) with the apparent rate constant k_app being a complex function of both initial nitrobenzene and thiophenol concentrations, as well as linearly dependent on the amount of solid catalyst used. A mechanism for this catalytic reaction consistent with the kinetic experiments as well as the observed properties of the intercalated molybdenum complex has thiophenol inducing the initial coupled proton–electron transfer steps to form an intercalated Mo^IV species, which is oxidized back to the parent Mo^VI complex by nitrobenzene via a two‐electron oxygen atom transfer reaction that yields nitrosobenzene. This mechanism is widespread in enzymatic catalysis and in model chemical reactions. The intermediate nitrosobenzene thus formed is reduced directly by excess thiophenol to aniline. The values of rate coefficients indicate that reduction of nitrobenzene proceeds much faster than proton‐assisted oxidation of thiophenol. This may account for the observation that the presence of protonic amberlite IR‐120(H) increases considerably the rate of the overall reaction catalyzed. Activation parameters in excess of the protonic resin and PhSH were ΔH^≠ = 80 kJ mol⁻¹ and ΔS^≠ = −70 J mol⁻¹ K⁻¹. The large negative activation entropy is consistent with an associative transition state. The present system is characterized by a well‐defined catalytic cycle with multiple‐turnovers reductions of nitrobenzene to aniline without appreciable deactivation. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 212–224, 2001     

Kinetic study of the ligand substitution on the trimethylplatinum(iv) complexes with unidentate ligands

Ligand substitution kinetics for the reaction [Pt^IVMe₃(X)(NN)]+NaY=[Pt^IVMe₃(Y)(NN)]+NaX, where NN=bipy or phen, X=MeO⁻, CH₃COO⁻, or HCOO⁻, and Y=SCN⁻ or N₃⁻, has been studied in methanol at various temperatures. The kinetic parameters for the reaction are as follows. The reaction of [PtMe₃(OMe)(phen)] with NaSCN: k₁=36.1±10.0 s⁻¹; ΔH₁^≠=65.9±14.2 kJ mol⁻¹; ΔS₁^≠=6±47 J mol⁻¹ K⁻¹; k₋₂=0.0355±0.0034 s⁻¹; ΔH₋₂^≠=63.8±1.1 kJ mol⁻¹; ΔS₋₂^≠=−58.8±3.6 J mol⁻¹ K⁻¹; and k₋₁/k₂=148±19. The reaction of [PtMe₃(OAc)(bipy)] with NaN₃: k₁=26.2±0.1 s⁻¹; ΔH₁^≠=60.5±6.6 kJ mol⁻¹; ΔS₁^≠=−14±22 J mol⁻¹K⁻¹; k₋₂=0.134±0.081 s⁻¹; ΔH₋₂^≠=74.1±24.3 kJ mol⁻¹; ΔS₋₂^≠=−10±82 J mol⁻¹K⁻¹; and k₋₁/k₂=0.479±0.012. The reaction of [PtMe₃(OAc)(bipy)] with NaSCN: k₁=26.4±0.3 s⁻¹; ΔH₁^≠=59.6±6.7 kJ mol⁻¹; ΔS₁^≠=−17±23 J mol⁻¹K⁻¹; k₋₂=0.174±0.200 s⁻¹; ΔH₋₂^≠=62.7±10.3 kJ mol⁻¹; ΔS₋₂^≠=−48±35 J mol⁻¹K⁻¹; and k₋₁/k₂=1.01±0.08. The reaction of [PtMe₃(OOCH)(bipy)] with NaN₃: k₁=36.8±0.3 s⁻¹; ΔH₁^≠=66.4±4.7 kJ mol⁻¹; ΔS₁^≠=7±16 J mol⁻¹K⁻¹; k₋₂=0.164±0.076 s⁻¹; ΔH₋₂^≠=47.0±18.1 kJ mol⁻¹; ΔS₋₂^≠=−101±61 J mol⁻¹ K⁻¹; and k₋₁/k₂=5.90±0.18. The reaction of [PtMe₃(OOCH)(bipy)] with NaSCN: k₁ =33.5±0.2 s⁻¹; ΔH₁^≠=58.0±0.4 kJ mol⁻¹; ΔS₁^≠=−20.5±1.6 J mol⁻¹ K⁻¹; k₋₂=0.222±0.083 s⁻¹; ΔH₋₂^≠=54.9±6.3 kJ mol⁻¹; ΔS₋₂^≠=−73.0±21.3 J mol⁻¹ K⁻¹; and k₋₁/k₂=12.0±0.3. Conditional pseudo-first-order rate constant k₀ increased linearly with the concentration of NaY, while it decreased drastically with the concentration of NaX. Some plausible mechanisms were examined, and the following mechanism was proposed. [Note to reader: Please see article pdf to view this scheme.] © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 523–532, 1998     

Synthesis and thermal decomposition kinetics of La(III) complexwith unsymmetrical Schiff base ligand

A new unsymmetrical solid Schiff base (LLi) was synthesized using L-lysine, o-vanillin and 2-hydroxy-l-naphthaldehyde. Solid lanthanum(III) complex of this ligand [LaL(NO₃)]NO₃·2H₂O have been prepared and characterized by elemental analyses, IR, UV and molar conductance. The thermal decomposition kinetics of the complex for the second stage was studied under non-isothermal condition by TG and DTG methods. The kinetic equation may be expressed as: dα/dt=Ae^−E/RT(1−α)². The kinetic parameters (E, A), activation entropy ΔS ^# and activation free-energy ΔG ^# were also gained.     

Solid-State Confinement Effects in Selective exo-H/D Exchange in the Rhodium σ-Norbornane Complex [(Cy2PCH2CH2PCy2)Rh(η2:η2-C7H12)][BArF4]

Density functional theory calculations modelling selective exo-H/D exchange observed in the Rh σ-alkane complex [(Cy₂PCH₂CH₂PCy₂)Rh(η²:η²-endo-NBA)][BAr^F₄], [1-NBA][BAr^F ₄ ] , are reported, where Ar^F=3,5-C₆H₃(CF₃)₂ and NBA=norbornane, C₇H₁₂. Two models were considered 1) an isolated molecular cation, [1-NBA]⁺ and 2) a full model in which [1-NBA][BAr^F ₄ ] is treated in the solid state through periodic DFT. After an initial endo-exo rearrangement, both models predict H/D exchange to proceed through D₂ addition and oxidative cleavage followed by a rate-limiting C−H activation of the norbornane through a σ-CAM step to form a [1-Rh(D)(η²-HD)(norbornyl)]⁺ intermediate. HD rotation followed by a σ-CAM C−D bond formation, HD reductive coupling and HD loss then complete the H/D exchange process. exo-H/D exchange is facilitated by a supporting agostic interaction and is consistently more accessible kinetically than the potentially competing endo-H/D exchange (isolated cation: ΔG^≠_exo=+15.9 kcal/mol, ΔG^≠_endo=+18.4 kcal/mol; solid state: ΔG^≠_exo=+22.1 kcal/mol, ΔG^≠_endo=+25.1 kcal/mol). The solid-state environment has a significant impact on the computed energetics, with barriers increasing by ca. 7 kcal/mol, while only the solid-state model correctly predicts the endo-bound NBA complex to be the resting state of the system. These outcomes reflect solid-state confinement effects within the pocket occupied by the [1-NBA]⁺ cation and defined by the pseudo-octahedral array of neighbouring [BAr^F₄]⁻ anions. The asymmetry of the solid-state environment also requires a second H/D exchange pathway to be defined to account for reaction at all four exo-C−H bonds. These entail slightly higher barriers (ΔG^≠_exo= +24.8 kcal/mol, ΔG^≠_endo=+27.5 kcal/mol) but retain a distinct preference for exo- over endo-H/D exchange.