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1.
The gas phase elimination kinetics of the title compound was studied over the temperature range of 260.1–315.0°C and pressure range of 20–70 Torr. This elimination, in seasoned static reaction system and in the presence of at least fourfold of the free radical inhibitor toluene, is homogeneous, unimolecular and follows a first‐order rate law. The reaction yielded mainly benzaldehyde, CO, and HBr, and small amounts of benzylbromide and CO2. The observed rate coefficients are expressed by the following Arrhenius equations: For benzaldehyde formation: log k1 (s−1) = (12.23 ± 0.26) − (164.9 ± 2.7) kJ mol−1 (2.303 RT)−1 For benzylbromide formation: log k1 (s−1) = (13.82 ± 0.50) − (192.8 ± 5.5) kJ mol−1 (2.303 RT)−1 The mechanisms are believed to proceed through a semi‐polar five‐membered cyclic transition state for the benzaldehyde formation, while a four‐centered cyclic transition state for benzylbromide formation. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 725–728, 1999  相似文献   

2.
Time-resolved kinetic studies of the reaction of silylene, SiH2, generated by 193 nm laser flash photolysis of silacyclopent-3-ene, have been carried out in the presence of ammonia, NH3. Second order kinetics were observed. The reaction was studied in the gas phase at 10 Torr total pressure in SF6 bath gas at each of the three temperatures, 299, 340 and 400 K. The second order rate constants (laser pulse energy of 60 mJ +) fitted the Arrhenius equation:noindent Experiments at other pressures showed that these rate constants were unaffected by pressure in the range 10–100 Torr, but showed small decreases in value at 3 and 1 Torr. There was also a weak intensity dependence, with rate constants decreasing at laser pulse energies of 30 mJ +. Ab initio calculations at the G3 level of theory, show that SiH2+NH3 should form an initial adduct (donor-acceptor complex), but that energy barriers are too great for further reaction of the adduct. This implies that SiH2+NH3 should be a pressure dependent association reaction. The experimental data are inconsistent with this and we conclude that SiH2 decays are better explained by reaction of SiH2 with the amino radical, NH2, formed by photodissociation of NH3 at 193 nm. The mechanism of this previously unstudied reaction is discussed.  相似文献   

3.
UV spectra of SF5 and SF5O2 radicals in the gas phase at 295 K have been quantified using a pulse radiolysis UV absorption technique. The absorption spectrum of SF5 was quantified from 220 to 240 nm. The absorption cross section at 220 nm was (5.5 ± 1.7) × 10−19 cm2. When SF5 was produced in the presence of O2 an equilibrium between SF5, O2, and SF5O2 was established. The rate constant for the reaction of SF5 radicals with O2 was (8 ± 2) × 10−13 cm3 molecule−1 s−1. The decomposition rate constant for SF5O2 was (1.0 ± 0.5) × 105 s−1, giving an equilibrium constant of Keq = [SF5O2]/[SF5][O2] = (8.0 ± 4.5) × 10−18 cm3 molecule−1. The SF5 O2 bond strength is (13.7 ± 2.0) kcal mol−1. The SF5O2 spectrum was broad with no fine structure and similar to the UV spectra of alkyl peroxy radicals. The absorption cross section at 230 nm was found to (3.7 ± 0.9) × 10−18 cm2. The rate constant of the reaction of SF5O2 with NO was measured to (1.1 ± 0.3) × 10−11 cm3 molecule−1 s−1 by monitoring the kinetics of NO2 formation at 400 nm. The rate constant for the reaction of F atoms with SF4 was measured by two relative methods to be (1.3 ± 0.3) × 10−11 cm3 molecule−1 s−1. © 1994 John Wiley & Sons, Inc.  相似文献   

4.
By conducting an excimer laser photolysis (193 and 248 nm) behind shock waves, three elementary reactions important in the oxidation of H2S have been examined, where, H, O, and S atoms have been monitored by the atomic resonance absorption spectrometry. For HS + O2 → products (1), the rate constants evaluated by numerical simulations are summarized as: k1 = 3.1 × 10−11exp|-75 kJ mol−1/RT| cm3molecule−1s−1 (T = 1400-1850 K) with an uncertainty factor of about 2. Direct measurements of the rate constants for S + O2 → SO + O (2), and SO + O2 → SO2 + O (3) yield k2 = (2.5 ± 0.6) × 10−11 exp|-(15.3 ± 2.5) kJ mol−1/RT| cm3molecule−1s−1 (T = 980-1610 K) and, k3 = (1.7 ± 0.9) × 10−12 exp|-(34 ± 11) kJ mol−1/RT| cm3molecule−1s−1 (T = 1130-1640 K), respectively. By summarizing these data together with the recent experimental results on the H(SINGLE BOND)S(SINGLE BOND)O reaction systems, a new kinetic model for the H2S oxidation process is constructed. It is found that this simple reaction scheme is consistent with the experimental result on the induction time of SO2 formation obtained by Bradley and Dobson. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 57–66, 1997.  相似文献   

5.
Substitution reactions of a Cl ligand in [SnCl2(tpp)] (tpp=5,10,15,20‐tetraphenyl‐21H,23H‐porphinato(2−)) by five organic bases i.e., butylamine (BuNH2), sec‐butylamine (sBuNH2), tert‐butylamine (tBuNH2), dibutylamine (Bu2NH), and tributylamine (Bu3N), as entering nucleophile in dimethylformamide at I=0.1M (NaNO3) and 30–55° were studied. The second‐order rate constants for the substitution of a Cl ligand were found to be (36.86±1.14)⋅10−3, (32.91±0.79)⋅10−3, (22.21±0.58)⋅10−3, (19.09±0.66)⋅10−3, and (1.36±0.08)⋅10−3 M −1s−1 at 40° for BuNH2, tBuNH2, sBuNH2, Bu2NH, and Bu3N, respectively. In a temperature‐dependence study, the activation parameters ΔH and ΔS for the reaction of [SnCl2(tpp)] with the organic bases were determined as 38.61±4.79 kJ mol−1 and −150.40±15.46 J K−1mol−1 for BuNH2, 40.95±4.79 kJ mol−1 and −143.75±15.46 J K−1mol−1 for tBuNH2, 30.88±2.43 kJ mol−1 and −179.00±7.82 J K−1mol−1 for sBuNH2, 26.56±2.97 kJ mol−1 and −194.05±9.39 J K−1mol−1 for Bu2NH, and 39.37±2.25 kJ mol−1 and −174.68±7.07 J K−1 mol−1 for Bu3N. From the linear rate dependence on the concentration of the bases, the span of k2 values, and the large negative values of the activation entropy, an associative (A) mechanism is deduced for the ligand substitution.  相似文献   

6.
Time‐resolved studies of chlorosilylene, ClSiH, generated by the 193 nm laser flash photolysis of 1‐chloro‐1‐silacyclopent‐3‐ene, are carried out to obtain rate constants for its bimolecular reaction with ethene, C2H4, in the gas‐phase. The reaction is studied over the pressure range 0.13–13.3 kPa (with added SF6) at five temperatures in the range 296–562 K. The second order rate constants, obtained by extrapolation to the high pressure limits at each temperature, fitted the Arrhenius equation: log(k/cm3 molecule?1 s?1)=(?10.55±0.10) + (3.86±0.70) kJ mol?1/RT ln10. The Arrhenius parameters correspond to a loose transition state and the rate constant at room temperature is 43 % of that for SiH2 + C2H4, showing that the deactivating effect of Cl‐for‐H substitution in the silylene is not large. Quantum chemical calculations of the potential energy surface for this reaction at the G3MP2//B3LYP level show that, as well as 1‐chlorosilirane, ethylchlorosilylene is a viable product. The calculations reveal how the added effect of the Cl atom on the divalent state stabilisation of ClSiH influences the course of this reaction. RRKM calculations of the reaction pressure dependence suggest that ethylchlorosilylene should be the main product. The results are compared and contrasted with those of SiH2 and SiCl2 with C2H4.  相似文献   

7.
The gas phase elimination kinetics of 2‐bromopropene was studied over the temperature range of 571–654 K and pressure range of 12–46 Torr using the seasoned static reaction system. Propyne was the only olefinic product formed and accounted for >98% of the reaction. This product was formed by homogeneous, unimolecular pathways with high‐pressure first‐order rate constant k given by the equation k = 1013.47 ± 0.6 exp?208.2 ± 6.7 (kJ mol?1)/RT. The error limits are 95% certainty limits. The observed Arrhenius parameters are consistent with the four centered activated complex. The presence of methyl group on α‐carbon lowers the activation energy by 41 kJ mol?1. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 1–5, 2007  相似文献   

8.
The gas phase reaction of OH radicals with hydrogen iodide (HI) has been studied using a Laser Photolysis-Resonance Fluorescence (LP-RF) apparatus, recently developed in our group. The measured rate constant at 298 K was (2.7 ± 0.2) × 10−11 cm3 molecule−1 s−1. This rate constant is compared with the ones of the reactions OH + HCl and OH + HBr. The role of the reaction OH + HI in marine tropospheric chemistry is discussed. In addition, the LP-RF apparatus was tested and validated by measuring the following rate constants (in cm3 molecule−1 s−1 units): 𝓀(OH + HNO3) = (1.31 ± 0.06) × 10−13 at p = 27 and 50 Torr of argon and 𝓀(OH + C3H8) = (1.22 ± 0.08) × 10−12. These rate constants are in very good agreement with the literature data.  相似文献   

9.
A laser photolysis–long path laser absorption (LP‐LPLA) experiment has been used to determine the rate constants for H‐atom abstraction reactions of the dichloride radical anion (Cl2) in aqueous solution. From direct measurements of the decay of Cl2 in the presence of different reactants at pH = 4 and I = 0.1 M the following rate constants at T = 298 K were derived: methanol, (5.1 ± 0.3)·104 M−1 s−1; ethanol, (1.2 ± 0.2)·105 M−1 s−1; 1‐propanol, (1.01 ± 0.07)·105 M−1 s−1; 2‐propanol, (1.9 ± 0.3)·105 M−1 s−1; tert.‐butanol, (2.6 ± 0.5)·104 M−1 s−1; formaldehyde, (3.6 ± 0.5)·104 M−1 s−1; diethylether, (4.0 ± 0.2)·105 M−1 s−1; methyl‐tert.‐butylether, (7 ± 1)·104 M−1 s−1; tetrahydrofuran, (4.8 ± 0.6)·105 M−1 s−1; acetone, (1.41 ± 0.09)·103 M−1 s−1. For the reactions of Cl2 with formic acid and acetic acid rate constants of (8.0 ± 1.4)·104 M−1 s−1 (pH = 0, I = 1.1 M and T = 298 K) and (1.5 ± 0.8) · 103 M−1 s−1 (pH = 0.42, I = 0.48 M and T = 298 K), respectively, were derived. A correlation between the rate constants at T = 298 K for all oxygenated hydrocarbons and the bond dissociation energy (BDE) of the weakest C‐H‐bond of log k2nd = (32.9 ± 8.9) − (0.073 ± 0.022)·BDE/kJ mol−1 is derived. From temperature‐dependent measurements the following Arrhenius expressions were derived: k (Cl2 + HCOOH) = (2.00 ± 0.05)·1010·exp(−(4500 ± 200) K/T) M−1 s−1, Ea = (37 ± 2) kJ mol−1 k (Cl2 + CH3COOH) = (2.7 ± 0.5)·1010·exp(−(4900 ± 1300) K/T) M−1 s−1, Ea = (41 ± 11) kJ mol−1 k (Cl2 + CH3OH) = (5.1 ± 0.9)·1012·exp(−(5500 ± 1500) K/T) M−1 s−1, Ea = (46 ± 13) kJ mol−1 k (Cl2 + CH2(OH)2) = (7.9 ± 0.7)·1010·exp(−(4400 ± 700) K/T) M−1 s−1, Ea = (36 ± 5) kJ mol−1 Finally, in measurements at different ionic strengths (I) a decrease of the rate constant with increasing I has been observed in the reactions of Cl2 with methanol and hydrated formaldehyde. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 169–181, 1999  相似文献   

10.
The kinetics of the reactions of ground state oxygen atoms with 1-pentene, 1-hexene, cis-2-pentene, and trans-2-pentene was investigated in the temperature range 200 to 370 K. In this range the temperature dependences of the rate constants can be represented by k = A′ Tn exp(− E′a/RT) with A′ = (1.0 ± 0.6) · 10−14 cm3 s−1, n = 1.13 ± 0.02, E′a = 0.54 ± 0.05 kJ mol−1 for 1-pentene: A′ = (1.3 ± 1.2) · 10−14 cm3 s−1, n = 1.04 ± 0.08, E′a = 0.2 ± 0.4 kJ mol−1 for 1-hexene; A′ = (0.6 ± 0.6) · 10−14 cm3 s−1, n = 1.12 ± 0.05, E′a = − 3.8 ± 0.8 kJ mol−1 for cis-2-pentene; and A′ = (0.6 ± 0.8) · 10−14 cm3 s−1, n = 1.14 ± 0.06, E′a = − 4.3 ± 0.5 kJ mol−1 for trans-2-pentene. The atoms were generated by the H2-laser photolysis of NO and detected by time resolved chemiluminescence in the presence of NO. The concentrations of the O(3P) atoms were kept so low that secondary reactions with products are unimportant. © 1997 John Wiley & Sons, Inc.  相似文献   

11.
Reactions of HCCCO and NCCO radicals with O2 have been studied by a combination of pulsed laser photolysis and photoionization mass spectrometry. HCCCO was produced by 193‐nm photolysis of methylpropiolate or 3‐butyn‐2‐one, and NCCO was formed by 193‐nm photolysis of acetylcyanide. The rate constants obtained at 298 ± 3 K were (6.5 ± 0.7) × 10?12 cm3 molecule?1 s?1 for the HCCCO + O2 reaction, and no pressure dependence was observed between 1.5 and 16 Torr of N2 as a bath gas. Because HCO and HCCO radicals were observed as reaction products, it was confirmed that the reaction proceeds by a two‐body reaction. On the other hand, the rate constants of NCCO with O2 depended on the total pressure and were (5.4–8.8) × 10?13 cm3 molecule?1 s?1 for total pressures 2.0–15.5 Torr of N2, confirming that the reaction proceeds by a three‐body process. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 440–448, 2001  相似文献   

12.
The kinetic of D,L-lactide polymerization in presence of biocompatible zirconium acetylacetonate initiator was studied by differential scanning calorimetry in isothermal mode at various temperatures and initiator concentrations. The enthalpy of D,L-lactide polymerization measured directly in DSC cell was found to be ΔH=−17.8±1.4 kJ mol−1. Kinetic curves of D,L-lactide polymerization and propagation rate constants were determined for polymerization with zirconium acetylacetonate at concentrations of 250–1000 ppm and temperature of 160–220 °C. Using model or reversible polymerization the following kinetic and thermodynamic parameters were calculated: activation energy Ea=44.51±5.35 kJ mol−1, preexponential constant lnA=15.47±1.38, entropy of polymerization ΔS=−25.14 J mol−1 K−1. The effect of reaction conditions on the molecular weight of poly(D,L-lactide) was shown.  相似文献   

13.
A theoretical kinetic study of the thermal decomposition of 1‐chlorohexane in gas phase between 600 and 1000 K was performed. Transition‐state theory and unimolecular reaction rate theory were combined with molecular information provided by quantum chemical calculations. Particularly, the B3LYP, BMK, M05–2X, and M06–2X formulations of the density functional theory (DFT) and the high‐level ab initio methods G3B3 and G4 were employed. The possible reaction channels for the thermal decomposition of 1‐chlorohexane were investigated, and the reaction takes place through the elimination of HCl with the formation of 1‐hexene. The derived high‐pressure limit rate coefficients are k (600–1000 K) = (8 ± 5) × 1013 exp[‐((56.7 ± 0.4) kcal mol−1/RT )] s−1. The pressure effect over the reaction was analyzed from the calculation of the low‐pressure limit rate coefficients and the falloff curves. In addition, the standard enthalpies of formation at 298 K of −46.9 ± 1.5 kcal mol−1 for 1‐chlorohexane and 5.8 ± 1.5 kcal mol−1 for C6H13 radical were derived from isodesmic and isogiric reactions at high levels of theory.  相似文献   

14.
Ligand substitution kinetics for the reaction [PtIVMe3(X)(NN)]+NaY=[PtIVMe3(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  相似文献   

15.
The technique of laser flash photolysis has been used to set limits on the rate constants for the bimolecular reactions of SiH2 with methane (CH4) and tetramethylsilane (SiMe4) at both ambient and elevated temperatures (ca 600 K). These limits show that the energy barriers to insertion reactions of SiH2 in the C H bonds of CH4 are at least 45(±6) kJ mol−1 and in the C H and/or Si C bonds of SiMe4 are at least 23(±6) kJ mol−1. The best thermochemical estimate of the activation energy for SiH2+CH4 is 59(±12) kJ mol−1. Reasons for the greatly diminished reactivity of SiH2 with C H as compared with Si H bonds are discussed. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 393–395, 1999  相似文献   

16.
The photoconversion of 2′,3′‐dihydro‐6‐nitro‐1′,3′,3′‐trimethylspiro[2H‐1‐benzopyran‐2,2′‐indole] ( Sp ) to its open merocyanine form ( Mc ) in a series of aerated cycloalkanes (cyclopentane, cyclohexane, and trans‐ and cis‐decalin) and of the protonated merocyanine ( McH + ) to Sp in aqueous solution were studied by laser‐induced optoacoustic spectroscopy (LIOAS). The +(11±2) ml mol−1 expansion determined for the ring closure is due to deprotonation of McH + plus the reaction of the ejected proton with the monoanion of malonic acid (added to stabilize Mc ), an intrinsic expansion and a small electrostriction term. The energy difference between Sp and initial McH + is (282±110) kJ mol−1. An intrinsic contraction of −(47±15) ml mol−1 occurs upon ring opening, forming triplet 3Mc in the cycloalkanes, whereas no volume change was detected for the 3Mc to Mc relaxation. Electrostriction decreases the 3Mc energy, (165±18) kJ mol−1, to 135 kJ mol−1. The difference in the values of the ring‐opening ( Sp to Mc ) reaction enthalpy in cycloalkanes as derived from the temperature dependence of the Sp ⇌ Mc equilibrium, (29±8) kJ mol−1, and from the LIOAS data, −(9±25) kJ mol−1, is due to the formation of Mc‐Sp aggregates during steady‐state measurements. The Sp ‐sensitized singlet molecular oxygen, O2(1Δg), quantum yield (average ΦΔ=0.58±0.03) derived from the near‐IR emission of O2(1Δg), was taken as a measure of Mc production in the cycloalkanes. These solvents, albeit troublesome in their handling, provide an additional series for the determination of structural volume changes in nonaqueous media, besides the alkanes already used.  相似文献   

17.
The reaction of Cl atoms with a series of C2–C5 unsaturated hydrocarbons has been investigated at atmospheric pressure of 760 Torr over the temperature range 283–323 K in air and N2 diluents. The decay of the hydrocarbons was followed using a gas chromatograph with a flame ionization detector (GC‐FID), and the kinetic constants were determined using a relative rate technique with n‐hexane as a reference compound. The Cl atoms were generated by UV photolysis (λ ≥ 300 nm) of Cl2 molecules. The following absolute rate constants (in units of 10−11 cm3 molecule−1 s−1, with errors representing ±2σ) for the reaction at 295 ± 2 K have been derived from the relative rate constants combined to the value 34.5 × 10−11 cm3 molecule−1 s−1 for the Cl + n‐hexane reaction: ethene (9.3 ± 0.6), propyne (22.1 ± 0.3), propene (27.6 ± 0.6), 1‐butene (35.2 ± 0.7), and 1‐pentene (48.3 ± 0.8). The temperature dependence of the reactions can be expressed as simple Arrhenius expressions (in units of 10−11 cm3 molecule−1 s−1): kethene = (0.39 ± 0.22) × 10−11 exp{(226 ± 42)/T}, kpropyne = (4.1 ± 2.5) × 10−11 exp{(118 ± 45)/T}, kpropene = (1.6 ± 1.8) × 10−11 exp{(203 ± 79)/T}, k1‐butene = (1.1 ± 1.3) × 10−11 exp{(245 ± 90)/T}, and k1‐pentene = (4.0 ± 2.2) × 10−11 exp{(423 ± 68)/T}. The applicability of our results to tropospheric chemistry is discussed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 478–484, 2000  相似文献   

18.
The thermal decomposition of 3-bromopropene was investigated in the temperature range 568.2–653.2 K and pressures between 14–64 Torr in static Pyrex reaction vessel. The reaction was shown to be homogeneous gas reaction of the first order with more than 60% conversion. For the overall reaction, E a = 153.67 ± 6.70 kJ mol?1, and logA (A, s?1) = 9.46 ± 0.57. Two mechanisms, dehydrohalogenation molecular elimination and C-Br bond fission are discussed, both of which account for the observed kinetics and products of decomposition. To interpret the fall-off behaviour, RRKM/ME calculations were adopted and the pressure dependent rate constants were calculated at collision efficiency of 0.25. From the pressure dependence study and RRKM calculations, it can be deduced that we are at the high-pressure limit.  相似文献   

19.
The kinetic and mechanistic study of Ag(I)‐catalyzed chlorination of linezolid (LNZ) by free available chlorine (FAC) was investigated at environmentally relevant pH 4.0–9.0. Apparent second‐order rate constants decreased with an increase in pH of the reaction mixture. The apparent second‐order rate constant for uncatalyzed reaction, e.g., kapp = 8.15 dm3 mol−1 s−1 at pH 4.0 and kapp. = 0.076 dm3 mol−1 s−1 at pH 9.0 and 25 ± 0.2°C and for Ag(I) catalyzed reaction total apparent second‐order rate constant, e.g., kapp = 51.50 dm3 mol−1 s−1 at pH 4.0 and kapp. = 1.03 dm3 mol−1 s−1 at pH 9.0 and 25 ± 0.2°C. The Ag(I) catalyst accelerates the reaction of LNZ with FAC by 10‐fold. A mechanism involving electrophilic halogenation has been proposed based on the kinetic data and LC/ESI/MS spectra. The influence of temperature on the rate of reaction was studied; the rate constants were found to increase with an increase in temperature. The thermodynamic activation parameters Ea, ΔH#, ΔS#, and ΔG# were evaluated for the reaction and discussed. The influence of catalyst, initially added product, dielectric constant, and ionic strength on the rate of reaction was also investigated. The monochlorinated substituted product along with degraded one was formed by the reaction of LNZ with FAC.  相似文献   

20.
Using a pulse-radiolysis transient UV–VIS absorption system, rate constants for the reactions of F atoms with CH3CHO (1) and CH3CO radicals with O2 (2) and NO (3) at 295 K and 1000 mbar total pressure of SF6 was determined to be k1=(1.4±0.2)×10−10, k2=(4.4±0.7)×10−12, and k3=(2.4±0.7)×10−11 cm3 molecule−1 s−1. By monitoring the formation of CH3C(O)O2 radicals (λ>250nm) and NO2 (λ=400.5nm) following radiolysis of SF6/CH3CHO/O2 and SF6/CH3CHO/O2/NO mixtures, respectively, it was deduced that reaction of F atoms with CH3CHO gives (65±9)% CH3CO and (35±9)% HC(O)CH2 radicals. Finally, the data obtained here suggest that decomposition of HC(O)CH2O radicals via C C bond scission occurs at a rate of <4.7×105 s−1. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 913–921, 1998  相似文献   

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