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1.
《Journal of Inorganic and Nuclear Chemistry》1981,43(7):1561-1564
The formation constants of the hydrolysis species of Pb(II) ion in D2O and H2OD2O mixtures containing 3 mol dm−3 LiClO4 were determined at 25°C by potentiometric titrations. The formation constants βp,q are smaller in D2O than in H2O, while the formation constants expressed by Kp,q in D2O have larger values than those in H2O. These results are consistent with those previously reported, which indicates that there exist some isotope effects other than that ascribed to the difference between ionic products of H2O and D2O. The formation constant of the tetramer Pb4(OL)44+ (L denotes H and D) decreased monotonously with the increase in the deuterium atom fraction. This variation was quantitatively interpreted in terms of the equilibrium theory of solvent deuterium isotope effects. 相似文献
2.
The kinetics of the isotope exchange reactions of RCH(COOH)2 (RH, D, Me, Et, Bu, and Ph) in D2O solution were studied by using 1H NMR spectroscopy. It was observed that the rate of isotope exchange reaction was inhibited by the presence of 1 M of DNO3, DCl, DBr or D2SO4 and catalyzed by the presence of 4 M of D2SO4. No inhibition effect was observed in the case of D3PO4. The effect of inorganic acids follows the order of D3PO4>D2SO4 ≫ (DNO3, DCl, DBr). The conjugated base (RCH(COOD)(COO−)) of RCH(COOD)2 plays an important role in the isotope exchange reaction. The presence of deuterium ion suppresses the generation of RCH(COOD)(COO−) ion from RCH(COOD)2 and inhibits the rate of isotope exchange. In general, the order of reactivity of RCH(COOH)2 toward isotope exchange with deuterium atom is RPh>(H, Br)>Me>(Et, Bu). © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 455–461, 1999 相似文献
3.
《Chemical physics letters》1986,127(4):347-353
Infrared multiphoton photooxidation of NH2D in NH3 mixtures was observed to produce exclusively HDO, suggesting a single step deuterium separation efficiency of [D2O]/([D20]+[H2O]) ⩾ 50% which is significantly higher than that of the theoretical value, 33%. The results are explained by the large rate differences in the radical scavenging steps, i.e. k(D+O2) = 2.2 × 109M−1 s−1, k(NH2+O2) ⩽ 5 × 106 M−1 s−1 and k(NH2+NH2)=1.6 × 1010 M−1 s−1. With Ti solid powder as a catalyst, we observed that the formation yields of HDO are at least three to four times higher than those without a catalyst. 相似文献
4.
《Chemical physics letters》1985,116(4):295-301
The value of the proton diffusion coefficient DH+ in ice was extracted from the diffusion-controlled rate kD of the proton recombination reaction RO− + H3O+ → kD ROH + H2O in polycrystalline doped ice. At −10°C, DH+ was estimated to lie between 3.5×10−6 and 1.3×10−5 cm2 s−1, well below the corresponding value of (4.1 ± 0.1)×10−5 cm2 s−1 found in supercooled water. 相似文献
5.
A. V. Willi 《Helvetica chimica acta》1966,49(5):1725-1728
Second order rate constants are determined for the E2 reactions of 2,2-diphenyl-ethyl benzenesulfonates Ph2CxHCH2O · O2S–C6H4–X with CH3ONa in methyl cellosolve solution (xH = H or D, X = p-CH3O, p-CH3, H or p-NO2). The HAMMETT ? values are of the same order of magnitude as those found in the first order solvolyses of methyl, ethyl or isopropyl benzenesulfonates. The primary deuterium isotope effects kH/kD are 5.27, 5.42 and 6.70 for X = p-CH3O, H and p-NO2. The ? values as well as the increase of kH/kD with introduction of p-NO2 supply evidence for simultaneous CαO and CβH bond cleavages also in the E2 reactions of these compounds. 相似文献
6.
The velocity of the hydrogen ion catalysed hydrolysis of p-nitrophenyl-diazo-methane (I) has been measured in H2O? D2O mixtures, giving an isotopic αi = 0.49. The product isotope effect r = 5.1, determined from product analyses, combined with the (overall) solvent isotope effect kH/kD = 2.81, yields the primary kinetic isotope effect (kH/kD)I = 3.8, and the secondary kinetic isotope effect (kH/kD)II = 0.75. The CICH2COOH-catalysed hydrolysis of I in H2O? D2O mixtures gave a straight-line plot of kn/kH versus the atomic fraction n of deuterium. With four carboxylic acids, as catalysts, values of about 4.3 for the kinetic (overall) isotope effects were observed. 相似文献
7.
It has been shown by ESR spectroscopy that the title reaction involves abstraction of hydrogen from the phosphite, since at ?10°C the reaction has a kinetic deuterium isotope effect, kH/kD, or ~3. The rate constant for hydrogen abstraction is c. 2 × 104 M?1 s?1. There is no significant addition of alkoxyl radicals to the phosphite. 相似文献
8.
《Journal of Photochemistry》1982,18(1):29-38
The reactivity of hydrogen atoms with liquid water was investigated by determination of the final products obtained by the photolysis (λ = 184.9 nm) of two systems in the range pH 10 – 13: (a) OH−/N2O/H2O and (b) OH−/H2O (air free). Based on the product yields of the two systems, non-linear fitting computations were performed including all possible reactions; a value of k(H + H2O) = 10 ± 2 dm3 mol−1 s−1 was determined. The share of each individual reaction leading to the formation of H2 was also deduced. 相似文献
9.
《Journal of Inorganic and Nuclear Chemistry》1979,41(9):1329-1331
The α-deuterium kinetic isotope effect in the solvolysis of ferrocenyl-1,1-dideuteriomethyltrimethylammonium iodide in aqueous solution has been measured. The isotope effect, kH/kD, is 1.06 ± 0.04 at 80°C (about 3% per deuterium atom). This effect is only a small fraction of the limiting α-deuterium isotope effect for a nitrogen leaving group, which is estimated to be about 20% per deuterium atom at 80°C. The small isotope effect supports the transition state model involving participation of the electrons localized on the iron atom. The activation parameters for the solvolysis reaction in the temperature range 70–90°C are: ΔH≠ = 132.6 ± 3.8 kJ mol−1 and ΔS≠ = 54.0 ± 20.1 JK−1 mol−1. 相似文献
10.
L. García Rodenas S. P. Alí S. J. Liberman 《Journal of Radioanalytical and Nuclear Chemistry》1990,141(2):289-294
The hydrogen isotope radiolytic yields, G(H2), G(HD) and G(D2) were determined in H2O/D2O mixtures under chemical conditions close to a LOCA in a PHWR like Atucha I Nuclear Station, that is 2·10–3 MH3BO3 and p(H+D)=8.5±0.2. The total hydrogen radiolytic yield G(H2+HD+D2) as a function of the deuterium atom fraction goes through a flat maximum at about 0.58. This result in dicates that the 4% flammability limit for hydrogen in the reactor's containment with be reached sooner than what is expected assuming a linear combination of pure H2 and D2 radiolytic yields. Hydrogen radiolytic production in 10–3 M KBr in H2O/D2O mixtures gives the same results as in the boric solutions suggesting a bimolecular B(OH)
4
–
+OH reaction. Identical isotope concentration factors were calculated for both solutions. 相似文献
11.
The overall rate constants for H-abstraction (kH) from tetrahydrofuran and D-abstraction (kD) from fully deuterated tetrahydrofuran by chlorine atoms in the temperature range of 298-547 K were determined. In both cases, very weak negative temperature dependences of the overall rate constants were observed, described by the expressions: kH = (1.55 ± 0.13) × 10−10 exp(52 ± 28/T) cm3 molecule−1 s−1 and kD = (1.27 ± 0.25) × 10−10exp(55 ± 62/T) cm3 molecule−1 s−1. The experimental results show that the value of the kinetic isotope effect (kH/kD), amounting to 1.21 ± 0.10, is temperature independent at 298-547 K. 相似文献
12.
The kinetic isotope effect for the abstraction of hydrogen/deuterium from dimethylnitramine and dimethylnitramine-d6 by chlorine atoms has been studied in the temperature range 273–353 K. The rate constant ratio kH0/kD is given by the Arrhenius expression, kH/kD=(0.92 ± 0.07)exp(286 ± 250/RT), where R is expressed in cal mol?1 K?1. The absolute rate constant for the deuterium abstraction reaction is extrapolated as kD=(1.50 ± 0.90) × 10?10 exp(?1,486 ± 370/RT) cm3 molecule?1 s?1. The temperature dependence of the kinetic isotope effect was calculated using the conventional transition-state theory, and the obtained values for kH/kD and ΔEH, D are in good agreement with the experimental value for a bent transition state geometry, with two new vibrational frequencies of 340 cm?1 (272 cm?1) corresponding to the in-plane and out-of-plane motions of hydrogen (deuterium) atoms in the Cl…H…C arrangement. © 1993 John Wiley & Sons, Inc. 相似文献
13.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1976,32(7):1387-1392
Equilibrium constants are reported for 26 light and 7 heavy phenols in terms of the usual equilibrium model of 1 : 1 complex formation. A solvation model sensitive to steric hindrance is also described. Linear correlations between log KH and ΔνOH as well as log KD and ΔνOH have been found for the interval: 30≤ΔνOH≤200 cm−1. These allow estimates on the equilibrium isotope effect. 相似文献
14.
Spectral simulation was used to analyze the molecular rovibrational bands of D2H and H2D at 5600 Å. These bands were previously measured by the ion beam neutralization method. They were assigned to the electronic 3p2B1 ? 2s2A1 and vibrational (ν - ν″) = (0, 0, 0,-0, 0, 0) transitions. Least squares fits to the experimental line-positions were made to determine the asymmetric rotator constants A, B and C for the 2s2A1 and 3p2B1 ν = 0 states of D2H and H2D, hitherto unknown. Lorentz line-profiles were assumed for the D2H and H2D rotational lines, whose widths are mainly governed by the lifetimes of the lower states. The bands at 5600 Å were simulated and the 2s2A1 state lifetimes were estimated to be σ ≥ 0.5 ± 0.2 ps for D2H and σ ≥ 0.4 ± 0.2 ps for H2D. Vibrational constants of D3 and D2H in the 2s2A1 states are determined from the positions of the 0-0 and 0-1 vibrational bands given in respective experimental spectra previously measured. For the first time the vibrational constants ω1 and ω2 of the 2s2A1 state of H2D were estimated from the positions of the 0-0 and 0-1 band maxima. These vibrational constants are compared with the corresponding vibrational constants of their ions. 相似文献
15.
At pH 2, the rate constant of hydrolysis of tris(tetraethylammonium) pentacyanoperoxynitritocobaltate(III) in H2O is 9.6×10−6 s−1. In the absence of any light, ONOO− is not replaced by H2O and isomerizes within the coordination sphere to NO3−. The novel complex [Co(CN)5NO3]3− released NO3− slowly, as detected by ion chromatography. At pH 6, no hydrolysis is observed. Direct photolysis, both at pH 2 and pH 6, of tris(tetraethylammonium) pentacyanoperoxynitritocobaltate(III) by irradiation (YAG laser) at 355 nm destroys the coordinated ONOO− and releases NO2., which hydrolyzes to NO3− and NO2−. We also measured the 59Co‐NMR spectra of [Co(CN)5OONO]3− and [Co(CN)5H2O]2−; the chemical shifts correspond very well to those predicted and are in agreement with the expected contribution to the ligand field by H2O and ONOO−. 相似文献
16.
Detlef Schröder Helena Florencio Waltraud Zummack Helmut Schwarz 《Helvetica chimica acta》1992,75(6):1792-1797
The reaction of FeO+ with toluene in the gas phase occurs at collision rate (kr = 1.36 × 10−9 cm3 molecule−1 s−1), and labeling experiments demonstrate that the total products due to C H bond activation involve to > 92% the benzylic position. In the ‘hydride’ abstraction process (formation of FeOH and C7H), the H-atom originates elusively from the benzylic position to generate a benzyl cation, and an intramolecular kinetic isotope effect kH/kD = 1.75 has been obtained. There is no evidence for the existence of isotopically sensitive branching (‘metabolic switching’) in the system studied. 相似文献
17.
Beat Freiermuth Bruno Hellrung Stefan Peterli Marie‐France Schultz David Wintgens Jakob Wirz 《Helvetica chimica acta》2001,84(12):3796-3809
The equilibrium between 10H‐anthr‐9‐one and 9‐anthrol favors the ketone, which ionizes as a carbon acid in aqueous base. Rates of equilibration were measured over the pH range 1 – 13 in aqueous solution (25°, ionic strength I=0. M ). Five independent thermodynamic and kinetic parameters were determined by analysis of the pH‐rate profile: the equilibrium constant of enolization, pKE=2.17, the ionization quotient of anthrol, pQ=7.84, and the rate constants of enolization catalyzed by acid, k=2.2⋅10−4 M −1 s−1, base, k=51.0 M −1 s−1, and water, k=1.21⋅10−5 s−1. Structure‐reactivity relationships strongly support the view that pH‐independent enolization of anthrone in water proceeds by rate‐determining ionization of the C‐acid. 相似文献
18.
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
19.
The rate constants for the gas‐phase SN2 reaction of F?(H2O) with CH3F have been calculated using the dual‐level variational transition state theory including multidimensional tunneling from 50 to 500 K. Tunneling was found to dominate the reaction below 200 K. The deuterium, 13C, and 14C kinetic isotope effects (KIEs) and solvent (D2O) isotope effects (SKIEs) were also calculated in the same temperature range. The results indicated that the deuterium and heavy water substitutions resulted in inverse KIEs (0.6~0.8 ) while the 13C and 14C substitutions resulted in normal KIEs (1.0~1.2) at room temperature. The calculated carbon KIEs increased significantly below 80 K due to the differences in the magnitude of the tunneling effects for different isotopic substitutions. 相似文献
20.
《Journal of Inorganic and Nuclear Chemistry》1981,43(11):2873-2879
Oxalato(amine)(trien)cobalt(III) and salicylato(amine)(trien)cobalt(III) perchlorates have been synthesized and tentatively assigned a cis α configuration. The dissociation constants of the complexes have been determined. The base hydrolysis of the complexes have been investigated at 30, 35, 38.6°C and I = 1.0 mol dm−3. The rate laws for the oxalato and salicylato complexes are −dln[Complex]T/dt = k2[OH−] and −dln[Complex]T = k1 + k2[OH−] respectively. For the oxalato complex, k2(30°C) = (2.95 ± 0.05) × 10−2 dm3 mol−1 s−1, ΔH1 = (109 ± 4) KJ mol−1, ΔS1 = (85 ± 13) JK−1 mol−1 and for the salicylato complex, k1(30°C) = (1.58 ± 0.28) × 10−4 s−1, ΔH1 = (166 ± 7) KJ mol−1, ΔS1 = (229 ± 21) JK−1 mol−1 and k2(30°C) = (3.56 ± 0.10) × 10−3 dm3 mol−1 s−1, ΔH1 = (101 ± 6) KJ mol−1, ΔS1 = (42 ± 20) JK−1 mol−1. The base hydrolysis reactions of the complexes were followed in presence of imidazole and ethanolamine, in the presence of added anions and also in D2O medium. The results are discussed in terms of δ SN1CB mechanism involving rate limiting CoO bond fission for both k1 and k2 paths. However, the possibility of CO bond cleavage in the base hydrolysis of the oxalato complex is not ruled out. 相似文献