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1.
The reactions have been studied competitively in the vapor phase over the range of 52–204°C. The i-C3F7 radicals were generated by means of the reaction It was found that where θ = 2.303RT J/mol. Absolute Arrhenius parameters are derived for the reactions where R = CF3, C2F5, and i-C3F7. 相似文献
2.
Jakelyne V. Coelho Matheus P. Freitas Cláudio F. Tormena Roberto Rittner 《Magnetic resonance in chemistry : MRC》2009,47(4):348-351
2‐Bromocyclohexanone is a model compound in which a 4JH2, H6 coupling constant is observed, whereas the corresponding 4JH2, H4 is absent. The observed long‐range coupling is not only a result of the known W‐type coupling, in the axial conformation, but also because of the less usual diaxial spin–spin coupling in the equatorial conformer. The carbonyl group plays a determining role in describing the coupling pathway, as concluded by natural bond orbital (NBO) analysis; although the and interactions in the axial conformer contribute for transmitting the spin information associated with the W‐type coupling, the strong and hyperconjugations in the equatorial conformer define an enhanced coupling pathway for 4JH2, H6, despite the inhibition of this coupling because of interaction and the large carbonyl angle. These findings provide the experimental evidence that orbital interactions contribute for the conformational isomerism of 2‐bromocyclohexanone. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
3.
Four titanium silanolates Ti(OSiR2R′)4 (1, R = Ph, R′ = tBu; 2, R = R′ = Ph; 3, R = R′ = iPr; 4, R = Me, R′ = tBu) were synthesised starting from Ti(OiPr)4 and the corresponding silanol, and their thermally induced decomposition was studied. Colourless single crystals of Ti(OSiPh Bu) CHCl C7H8 ( CHCl C7H8) were obtained from a mixture of chloroform and toluene (1:1) at ?20 °C. The compound crystallizes in the space group R3 c with Z = 18. The metal atom shows an almost ideal tetrahedral coordination, as is demonstrated by the O? Ti? O angles of 108.4(1)–111.1(1)°. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
4.
Wing Tsang 《国际化学动力学杂志》1976,8(2):173-192
3,3-Dimethylbutanol-2 (3,3-DMB-ol-2) and 2,3-dimethylbutanol-2 (2,3-DMB-ol-2) have been decomposed in comparative-rate single-pulse shock-tube experiments. The mechanisms of the decompositions are The rate expressions are They lead to D(iC3H7? H) – D((CH3)2(OH) C? H) = 8.3 kJ and D(C2H5? H) – D(CH3(OH) CH? H) = 24.2 kJ. These data, in conjunction with reasonable assumptions, give and The rate expressions for the decomposition of 2,3-DMB-1 and 3,3-DMB-1 are and 相似文献
5.
Wing Tsang 《国际化学动力学杂志》1978,10(1):41-66
Tertiary-amyl amine has been decomposed in single-pulse shock-tube experiments. Rate expressions for several of the important primary steps are This leads to D(CH3? H) – D(NH2? H) = ?10.5 kJ and D[(CH3)3C? H] – D[(CH3)2NH2C? H] = + 6 kJ. The present and earlier comparative rate single-pulse shock-tube data when combined with high-pressure hydrazine decomposition results-(after correcting for fall off effects through RRKM calculations) gives where kr(…) is the recombination rate involving the appropriate radicals. This suggests that in this context amino radical behavior is analogous to that of alkyl radicals. If this agreement is exact, then Rate expressions for the primary step in the decomposition of a variety of primary amines have been computed. In the case of benzyl amine where data exist the agreement is satisfactory. The following differences in bond energies have been estimated: 相似文献
6.
The photolysis of cis-1,2-dichloroethylene has been investigated in the presence of I2 as a function of incident wavelength and as a function of initial cis pressure. The results indicate that at ± > 2200Å the following primary processes occur: The lifetime of the excited state yielding the above products is estimated at about 2.4×10?9 sec. At shorter wavelengths additional C2H2 is produced by decomposition of a vibrationally excited C2H2Cl radical. Scavenging of the CHClCH radical by I2 produced trans and cis-CHClCHl in a ratio of 4 to 1, respectively. 相似文献
7.
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 + γP products). The experimental results can be explaned by the following mechanism: P and X represent the products and the added gases: 相似文献
8.
Wing Tsang 《国际化学动力学杂志》1978,10(6):599-617
Cyclopentane has been decomposed in comparative-rate single-pulse shock-tube experiments. The pyrolytic mechanism involves isomerization to 1-pentene and also a minor pathway leading to cyclopropane and ethylene. This is followed by the decomposition of 1-pentene and cyclopropane. The rate expressions over the temperature range of 1000°–1200° K are Details of the cyclopentane decomposition processes are considered, and it appears that if the trimethylene radical is an intermediate, then ΔHf(trimethylene) ≤ 280 kJ/mol at 300°K. 相似文献
9.
Chuanbo Gao Yasuhiro Sakamoto Dr. Osamu Terasaki Prof. Shunai Che Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(36):11423-11428
The synthesis system for mesophase formation, using the diprotic anionic surfactant N‐myristoyl‐L ‐glutamic acid (C14GluA) as the structure‐directing agent (SDA) and N‐trimethoxylsilylpropyl‐N,N,N‐trimethylammonium chloride (TMAPS) as the co‐structure‐directing agent (CSDA), has been investigated and a full‐scaled synthesis‐field diagram is presented. In this system we have obtained mesophases including three‐dimensional (3D) micellar cubic Fm m, Pm n, Fd m, micellar tetragonal P42/mnm, two‐dimensional (2D) hexagonal p6mm and bicontinuous cubic Pn m, by varying the C14GluA/NaOH/TMAPS composition ratios. From the diagram it can be concluded that the mesophase formation is affected to a high degree by the organic/inorganic‐interface curvature and the mesocage–mesocage electrostatic interaction. Bicontinuous cubic and 2D‐hexagonal phases were found in the low organic/inorganic‐interface curvature zones, whereas micellar cubic and tetragonal mesophases were found in the high organic/inorganic‐interface curvature zones. Formation of cubic Fm m and tetragonal P42/mnm was favoured in highly alkaline zones with strong mesocage–mesocage interactions, and formation of cubic Pm n and Fd m was favoured with moderate mesocage–mesocage interactions in the less alkaline zones of the diagram. 相似文献
10.
Wing Tsang 《国际化学动力学杂志》1978,10(7):687-711
4-Methylhexyne-1, 5-methylhexyne-1, hexyne-1, and 6-methylheptyne-2 have been decomposed in comparative-rate single-pulse shock-tube experiments. Rate expressions for the initial decomposition reactions at 1100°K and from 2 to 6 atm pressure are In combination with previous results, rate expressions for propargyl C? C bond cleavage are related to that for the alkanes by the expression These results yield a propargyl resonance energy of D(nC3H7-H) – D(C3H3-H) = 36 ± 2 kJ, in excellent agreement with a previous shock-tube study. They also lead to D(CH3C≡CCH2-H) – D(C3H3-H) = 0.6 ± 3 kJ, D(sC4H9-H) – D(iC3H7-H) = 0 ± 3 kJ, D(iC4H9-H) – D(nC3H7-H) = 2 ± 3 kJ, and D(nC3H7-H) – D(iC3H7-H) = 13.9 ± 3 kJ (all values are for 300°K). The systematics of the molecular decomposition process are explored. 相似文献
11.
Dr. Antoine Demont Dr. Carmelo Prestipino Dr. Olivier Hernandez Dr. Erik Elkaïm Serge Paofai Prof. Nikolaï Naumov Dr. Bruno Fontaine Prof. Régis Gautier Dr. Stéphane Cordier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12711-12719
The crystal structure of Cs2BaTa6Br15O3 has been elucidated by using synchrotron X‐ray powder diffraction and absorption experiments. It is built from edge‐bridged octahedral [(Ta6${{\rm Br}{{{\rm i}\hfill \atop 9\hfill}}}$ ${{\rm O}{{{\rm i}\hfill \atop 3\hfill}}}$ )${{\rm Br}{{{\rm a}\hfill \atop 6\hfill}}}$ ]4? cluster units with a singular poor metallic electron (ME) count equal to thirteen. This leads to a paramagnetic behaviour related to one unpaired electron. The arrangement of the Ta6 clusters is similar to that of Cs2LaTa6Br15O3 exhibiting 14‐MEs per [(Ta6${{\rm Br}{{{\rm i}\hfill \atop 9\hfill}}}$ ${{\rm O}{{{\rm i}\hfill \atop 3\hfill}}}$ )${{\rm Br}{{{\rm a}\hfill \atop 6\hfill}}}$ ]5? motif. The poorer electron‐count cluster presents longer metal–metal distances as foreseen according to the electronic structure of edge‐bridged hexanuclear cluster. Density functional theory (DFT) calculations on molecular models were used to rationalise the structural properties of 13‐ and 14‐ME clusters. Periodic DFT calculations demonstrate that the electronic structure of these solid‐state compounds is related to those of the discrete octahedral units. Oxygen–barium interactions seem to prevent the geometry of the octahedral cluster to strongly distort, allowing stabilisation of this unprecedented electron‐poor Ta6 cluster in the solid state. 相似文献
12.
The solubility equilibrium of α-GaO(OH) has been investigated at 60°C in solutions of perchloric acid having a constant ionic strength I = 3 m (Na, H)ClO4. The hydrogen ion concentration of the equilibrated solutions was measured with a glass electrode and the concentration of the dissolved GaIII was determined by chelometric titration. The experimental data can be explained by assuming the equilibrium . 相似文献
13.
Wing Tsang 《国际化学动力学杂志》1970,2(1):23-36
Dilute mixtures of 4-methyl-l-pentyne have been pyrolyzed in a single-pulse shock tube. The decomposition process involves bond breaking: as well as a molecular reaction: The rate parameters are: The heat of formation of propynyl radical is thus ΔHf300 = 338 kJ mol?1 (80.7 kcal mol?1)˙ This leads to a propynyl resonance energy of 40 kJ mol?1 (9.6 kcal mol?1). 相似文献
14.
The kinetics of the thermal decomposition of CF3O3CF3 has been investigated in the pressure range of 15–599 torr at temperatures between 59.8 and 90.3°C and also in the presence of CO between 42 and 7°C. The reaction is homogeneous. In the absence of CO the only reaction products are CF3O2CF3 and O2. The rate of reaction is strictly proportional to the trioxide pressure, and is not affected by the total pressure, the presence of inert gases, and oxygen. The following mechanism explains the experimental results: In the presence of CO there appear CO2, (CF3OCO)2, and CF3O2C(O)OCF3 as products. With increasing temperature the amount of peroxicarbonate decreases, while the amounts of oxalate and CO2 increase. The rate of decomposition of the trioxide above a limiting pressure of about 10 torr CO is strictly first order and independent of CO pressure, total pressure, and the pressure of the products. The addition of larger amounts of O2 to the CO containing system chaqnges the course of the reaction. 相似文献
15.
J. Czarnowski 《国际化学动力学杂志》1986,18(12):1323-1331
The thermal addition of CF3O3CF3(T) to CF2CCl2(E) has been investigated between 49.6 and 69.5°C. The initial pressure of CF3O3CF3 was varied between 7 and 240 torr and that of CF2CCl2 between 4 and 600 torr. Four products of formula CF3O(E)j OOCF3, where j = 1 → 4 are formed. The sum of the products Σ CF3O(E)jOOCF3 is equal to the amount of trioxide decomposed. The reaction is homogeneous. Its rate is not affected by the total pressure and the presence of inert gas. It is a free radical telomerization with four basic steps: thermal decomposition of CF3O3CF3 into CF3O. and CF3O2., chain initiation by addition of CF3O. to olefin incorporated in, and telomeric radicals termination. The consumption of alkene is well represented by the equation: where (d[E]/d[T]) = is the mean chain length of telomerization. varies from 1.45 at 1.5 torr of E to 3.3 at 400 torr of E. Above this pressure E has no influence on . The estimated value of the constant for the addition of telomeric radicals to alkene is: 相似文献
16.
The dispersive component of the surface‐free energy, , of cellulose acetate butyrate (CAB) has been determined using the net retention volume, VN, of n‐alkanes (C5? C8) probes in the temperature range 323.15–393.15 K. The values decrease nonlinearly with increase in temperature, and the temperature coefficients of are ? 0.32 (mJ/m2K) and ? 0.10 (mJ/m2K) in the range 323.15–353.15 K and 353.15–393.15 K, respectively. This variation in has been attributed to the structural changes that take place on the surface of CAB at ~353.15 K. The specific components of the enthalpy of adsorption, , and entropy of adsorption, , calculated using VN of polar solutes are negative. The values are used to evaluate Lewis acidity constant, Ka, and Lewis basicity constant, Kb, for the CAB surface. The Ka and Kb values are found to be 0.126 and 1.109, respectively, which suggest that the surface is predominantly basic. The Ka and Kb results indicate for the necessary surface modifications of CAB which act as biodegradable adsorbent material. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
17.
Mamoru Ohashi Takashi Lino Tomoyuki Takahashi Michiaki Yoneda Soichiro Kyushin Kazuo Tsujimoto 《Journal of mass spectrometry : JMS》1990,25(2):109-114
Liquid secondary ion mass spectra of choline and acetylcholine halides exhibit several series of cluster ions whose origins were investigated using B/E and B2/E linked-scan techniques. In the case of choline halides three series of cluster ions were identified as (Me3$ \mathop {\rm N}\limits^ + $CH2CH2OH + nM), (Me3$ \mathop {\rm N}\limits^ + $CH2CH2OMe + nM) and (Me3N$ \mathop {\rm N}\limits^ + $CH2CH2OH · Me3$ \mathop {\rm N}\limits^ + $CH2CH2O? + nM), while (CH3COOCH2CH2$ \mathop {\rm N}\limits^ + $Me3 + nM), (Me3$ \mathop {\rm N}\limits^ + $CH2CH2OH + nM) and (CH2 = CH$ \mathop {\rm N}\limits^ + $Me3 + nM) were observed in the spectra of acetylcholine halides. For these cluster ions, bimolecular reactions induced on ion bombardment under secondary ion mass spectrometric conditions are discussed. 相似文献
18.
O(1D), produced from the photolysis of N2O at 2139 Å, reacts with N2O in accord with: We have used the method of chemical difference to obtain an accurate measure of k2/k3 = 0.59 ± 0.01. Furthermore, the quantum yield of production of O(3P), either on direct photolysis or on deactivation of O(1D) by N2O, is less than 0.02 and probably zero. 相似文献
19.
The Sublimation and the Thermal Decomposition of TeJ4 and the Existence of TeJ2 in the Gaseous Phase The sublimation and the decomposition of TeJ4 have been investigated. For the sublimation and the decomposition reactions and the values of enthalpy and entropy were derived (see ?Inhaltsübersicht”?). The existence of TeJ2 in the gaseous phase was demonstrated by equilibrium measurements and chemical transport experiments. 相似文献
20.
Dr. Anurag Mishra Sunmi Lee Dr. Hyunuk Kim Dr. Timothy R. Cook Prof. Peter J. Stang Prof. Ki‐Whan Chi 《化学:亚洲杂志》2012,7(11):2592-2599
Two new large molecular rectangles ( 4 and 5 ) were obtained by the reaction of two different dinuclear arene ruthenium complexes [Ru2(arene)2(O O)2Cl2] (arene=p‐cymene; O O=2,5‐dihydroxy‐1,4‐benzoquinonato ( 2 ), 6,11‐dihydroxy‐5,12‐naphthacene dionato ( 3 )) with the unsymmetrical amide (N‐[4‐(pyridin‐4‐ylethynyl)phenyl]isonicotinamide) donor ligand 1 in methanol in the presence of AgO3SCF3, forming tetranuclear cations of the general formula [Ru4(arene)4( )2(O O)2]4+. Both rectangles were isolated in good yields as triflate salts and were characterized by multinuclear NMR, ESI‐MS, UV/Vis, and photoluminescence spectroscopy. The crystal structure of 5 was determined by X‐ray diffraction. Luminescent rectangle 5 was used for anion sensing with an amide ligand as a hydrogen‐bond donor and an arene–ruthenium acceptor as a signaling unit. Rectangle 5 strongly bound multicarboxylate anions, such as oxalate, tartrate, and citrate, in UV/Vis titration experiments in 1:1 ratios, in contrast to monoanions, such as F?, Cl?, NO3?, PF6?, CH3COO?, and C6H5COO?. The fluorescence titration experiment showed a large fluorescence enhancement of 5 upon binding to multicarboxylate anions, which could be attributed to blocking of the photoinduced electron transfer process from the arene–ruthenium moiety to the amidic donor in 5 ; this was likely to be a result of hydrogen bonding between the ligand and the anion. On the other hand, rectangle 5 was not selective towards any other anions. To the naked eye, multicarboxylate anions in a solution of 5 in methanol appear greenish upon irradiation with UV light. 相似文献