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1.
Ethene and two kinds of nitrating reagents (HNO3 and N2O5) were included in respective molecular systems, which progressed through a two‐stage electrophilic and free radical nitrosubstitution, resulting in the corresponding nitroethene compounds. Subsequent halogenation (using Cl2 and Br2) and amination (using ammonia) were then performed, also by electrophilic and radical substitution, to produce the target 1,1‐diamino‐2,2‐dinitroethene (FOX‐7) derivatives. All transition state species were identified using a two‐ or three‐structure Synchronous Transit‐Guided Quasi‐Newton between the Cartesian coordinates of the related molecular systems at specific reaction stages. The modeling results suggest that N2O5 is the better agent for nitration and bromine is suitable for use in halogenation. The comparable activation energies throughout the reaction stages were considered to imply the most feasible pathways of FOX‐7 synthesis. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010  相似文献   

2.
Mononitrotoluene (MNT) was incorporated into solvated reaction systems and was subjected to subsequent nitration (electrophilic and free radical substitution) to obtain corresponding dinitrotoluene (DNT) and trinitrotoluene (TNT) products. In the electrophilic nitration system, the energy barrier of the reaction to produce o,p‐dinitrotoluene from p‐nitrotoluene was found to decrease from 62.7 to 14.7 kJ/mol to 9.2 kJ/mol in solventless, hydrated, and methanol‐solvated molecular reaction systems, respectively. Further nitration to produce TNT in related solventless and solvated systems also led to a stepwise decreasing trend in the required energy, from 297.6 to 118.6 kJ/mol to 42.8 kJ/mol. Comparative synthesis using ·NO2 as the nitrating reagent to obtain o,p‐DNT or TNT in the hydrated system shows a lower reaction energy barrier than that of the same reaction in the solventless system. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009  相似文献   

3.
The reaction of 3-substituted indoles with 2-cyclohexenone under Lewis acid mediated conditions with Bi(NO3)3·5H2O has been investigated. We have demonstrated that electrophilic substitution of 3-substituted indoles with 2-cyclohexenone will readily occur at the nitrogen. Furthermore, the extent of regioselectivity is dependent on reaction solvent and the C3-substituent. Excellent conversion is obtained with good to excellent isolated yields of N- and C2-adducts. In general, more polar, aprotic solvents (CH3CN) give greater N-selectivity whereas with polar protic solvents (CH3OH) an increase in the C2-adduct is observed.  相似文献   

4.
The gaseous reaction of oxygen atoms with dimethylamine was studied in a cross-jet reactor and found to proceed by electrophilic addition to form an energy-rich N-oxide which rearranges to an hydroxylamine and then decomposes via three routes: (CH3)2 N + OH, CH3NCH2 + H2O and CH3NHO + CH3.  相似文献   

5.
Kinetic study on the cleavage of N‐(4′‐methoxyphenyl)phthalamic acid (NMPPAH) in mixed H2O‐CH3CN and H2O‐1,4‐dioxan solvents containing 0.05 M HCl reveals the formation of phthalic anhydride (PAn)/phthalic acid (PA) as the sole or major product. Pseudo first‐order rate constants (k1) for the conversion of NMPPAH to PAn decrease nonlinearly from 60.4 × 10?5 to 2.64 × 10?5 s?1 with the increase in the contents of 1,4‐dioxan from 10 to 80% v/v in mixed aqueous solvents. The rate of cleavage of NMPPAH in mixed H2O‐CH3CN solvents at ≥50% v/v CH3CN follows an irreversible consecutive reaction path: NMPPAH PA. The values of k1 are larger in H2O‐CH3CN than in H2O‐1,4‐dioxan solvents. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 316–325, 2004  相似文献   

6.
[Fe]‐hydrogenase has a single iron‐containing active site that features an acylmethylpyridinol ligand. This unique ligand environment had yet to be reproduced in synthetic models; however the synthesis and reactivity of a new class of small molecule mimics of [Fe]‐hydrogenase in which a mono‐iron center is ligated by an acylmethylpyridinol ligand has now been achieved. Key to the preparation of these model compounds is the successful C?O cleavage of an alkyl ether moiety to form the desired pyridinol ligand. Reaction of solvated complex [(2‐CH2CO‐6‐HOC5H3N)Fe(CO)2(CH3CN)2]+(BF4)? with thiols or thiophenols in the presence of NEt3 yielded 5‐coordinate iron thiolate complexes. Further derivation produced complexes [(2‐CH2CO‐6‐HOC5H3N)Fe(CO)2(SCH2CH2OH)] and [(2‐CH2CO‐6‐HOC5H3N)Fe(CO)2(CH3COO)], which can be regarded as models of FeGP cofactors of [Fe]‐hydrogenase extracted by 2‐mercaptoethanol and acetic acid, respectively. When the derivative complexes were treated with HBF4?Et2O, the solvated complex was regenerated by protonation of the thiolate ligands. The reactivity of several models with CO, isocyanide, cyanide, and H2 was also investigated.  相似文献   

7.
The specific fluorescence properties of morin (3,2′,4′,5,7‐pentahydroxyflavone) were studied in various CH3OH–H2O and CH3CN–H2O mixed solvents. Although the dihedral angle is large in the S0 state, morin has an almost planar molecular structure in the S1 state owing to the very low rotational energy barrier around the interring bond between B and the A, C ring. The excited state intramolecular proton transfer (ESIPT) at the S1 state cannot occur immediately after excitation, S1 → S0 fluorescence can be observed. Two conformers, Morin A and B have been known. At the CH3OH–H2O, Morin B will be the principal species but at the CH3CN–H2O, Morin A is the principal species. At the CH3OH–H2O, owing to the large Franck–Condon (FC) factor for S2 → S1 internal convernal (IC) and flexible molecular structure, only S1 → S0 fluorescence was exhibited. At the CH3CN–H2O, as the FC factor for S2 → S1 IC is small and molecular structure is rigid, S2 → S0 and S1 → S0 dual fluorescence was observed. This abnormal fluorescence property was further supported by the small pK1 value, effective delocalization of the lone pair electrons of C(2′)–OH to the A, C ring, and a theoretical calculation.  相似文献   

8.
Heats of reaction and barrier heights have been computed for H + CH2CH2 → C2H5, H + CH2O → CH3O, and H + CH2O → CH2OH using unrestricted Hartree-Fock and Møller–Plesset perturbation theory up to fourth order (with and without spin annihilation), using single-reference configuration interaction, and using multiconfiguration self-consistent field methods with 3-21G, 6-31G(d), 6-31G(d,p), and 6-311G(d,p) basis sets. The barrier height in all three reactions appears to be relatively insensitive to the basis sets, but the heats of reaction are affected by p-type polarization functions on hydrogen. Computation of the harmonic vibrational frequencies and infrared intensities with two sets of polarization functions on heavy atoms [6-31G(2d)] improves the agreement with experiment. The experimental barrier height for H + C2H4 (2.04 ± 0.08 kcal/mol) is overestimated by 7?9 kcal/mol at the MP2, MP3, and MP4 levels. MCSCF and CISD calculations lower the barrier height by approximately 4 kcal/mol relative to the MP4 calculations but are still almost 4 kcal/mol too high compared to experiment. Annihilation of the largest spin contaminant lowers the MP4SDTQ computed barrier height by 8?9 kcal/mol. For the hydrogen addition to formaldehyde, the same trends are observed. The overestimation of the barrier height with Møller-Plesset perdicted barrier heights for H + C2H4 → C2H5, H + CH2O → CH3O, and H + CH2O → CH2OH at the MP4SDTQ /6-31G(d) after spin annihilation are respectively 1.8, 4.6, and 10.5 kcal/mol.  相似文献   

9.
The gas‐phase reaction mechanism between methane and rhodium monoxide for the formation of methanol, syngas, formaldehyde, water, and methyl radical have been studied in detail on the doublet and quartet state potential energy surfaces at the CCSD(T)/6‐311+G(2d, 2p), SDD//B3LYP/6‐311+G(2d, 2p), SDD level. Over the 300–1100 K temperature range, the branching ratio for the Rh(4F) + CH3OH channel is 97.5–100%, whereas the branching ratio for the D‐CH2ORh + H2 channel is 0.0–2.5%, and the branching ratio for the D‐CH2ORh + H2 channel is so small to be ruled out. The minimum energy reaction pathway for the main product methanol formation involving two spin inversions prefers to both start and terminate on the ground quartet state, where the ground doublet intermediate CH3RhOH is energetically preferred, and its formation rate constant over the 300–1100 K temperature range is fitted by kCH3RhOH = 7.03 × 106 exp(?69.484/RT) dm3 mol?1 s?1. On the other hand, the main products shall be Rh + CH3OH in the reactions of RhO + CH4, CH2ORh + H2, Rh + CO +2H2, and RhCH2 + H2O, whereas the main products shall be CH2ORh + H2 in the reaction of Rh + CH3OH. Meanwhile, the doublet intermediates H2RhOCH2 and CH3RhOH are predicted to be energetically favored in the reactions of Rh + CH3OH and CH2ORh + H2 and in the reaction of RhCH2 + H2O, respectively. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010  相似文献   

10.
A bimolecular rate constant,kDHO, of (29 ± 9) × 10?12 cm3 molecule?1 s?1 was measured using the relative rate technique for the reaction of the hydroxyl radical (OH) with 3,5‐dimethyl‐1‐hexyn‐3‐ol (DHO, HC?CC(OH)(CH3)CH2CH(CH3)2) at (297 ± 3) K and 1 atm total pressure. To more clearly define DHO's indoor environment degradation mechanism, the products of the DHO + OH reaction were also investigated. The positively identified DHO/OH reaction products were acetone ((CH3)2C?O), 3‐butyne‐2‐one (3B2O, HC?CC(?O)(CH3)), 2‐methyl‐propanal (2MP, H(O?)CCH(CH3)2), 4‐methyl‐2‐pentanone (MIBK, CH3C(?O)CH2CH(CH3)2), ethanedial (GLY, HC(?O)C(?O)H), 2‐oxopropanal (MGLY, CH3C(?O)C(?O)H), and 2,3‐butanedione (23BD, CH3C(?O)C(?O)CH3). The yields of 3B2O and MIBK from the DHO/OH reaction were (8.4 ± 0.3) and (26 ± 2)%, respectively. The use of derivatizing agents O‐(2,3,4,5,6‐pentalfluorobenzyl)hydroxylamine (PFBHA) and N,O‐bis(trimethylsilyl)trifluoroacetamide (BSTFA) clearly indicated that several other reaction products were formed. The elucidation of these other reaction products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible DHO/OH reaction mechanisms based on previously published volatile organic compound/OH gas‐phase reaction mechanisms. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 534–544, 2004  相似文献   

11.
The transition states of the reaction of electrophilic substitution in a series of ortho-, meta-, and para-carboranes were found by calculations in the B3PW91/6-31G(d,p) and B3LYP/6-31G(d,p) approximations. The key role of catalyst was demonstrated in the reactions of halogenation and alkylation. The reaction selectivity of electrophilic alkylation by CH3Br in the presence of AlCl3 should be lower than that of the chlorination reaction.  相似文献   

12.
In this investigation, reaction channels of weakly bound complexes CO2…HF, CO2…HF…NH3, CO2…HF…H2O and CO2…HF…CH3OH systems were established at the B3LYP/6‐311++G(3df,2pd) level, using the Gaussian 98 program. The conformers of syn‐fluoroformic acid or syn‐fluoroformic acid plus a third molecule (NH3, H2O, or CH3OH) were found to be more stable than the conformers of the related anti‐fluoroformic acid or anti‐fluoroformic acid plus a third molecule (NH3, H2O, or CH3OH). However, the weakly bound complexes were found to be more stable than either the related syn‐ and anti‐type fluoroformic acid or the acid plus third molecule (NH3, H2O, or CH3OH) conformers. They decomposed into CO2 + HF, CO2 + NH4F, CO2 + H3OF or CO2 + (CH3)OH2F combined molecular systems. The weakly bound complexes have four reaction channels, each of which includes weakly bound complexes and related systems. Moreover, each reaction channel includes two transition state structures. The transition state between the weakly bound complex and anti‐fluoroformic acid type structure (T13) is significantly larger than that of internal rotation (T23) between the syn‐ and anti‐FCO2H (or FCO2H…NH3, FCO2H…H2O, or FCO2H…CH3OH) structures. However, adding the third molecule NH3, H2O, or CH3OH can significantly reduce the activation energy of T13. The catalytic strengths of the third molecules are predicted to follow the order H2O < NH3 < CH3OH. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006  相似文献   

13.
The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to explore the reaction of (CH3)3In with O3 over a range of time scales. Upon twin jet deposition (short reaction time), formation of the novel H3COIn(CH3)2 species along with a low yield of CH2O was observed. Subsequent UV irradiation greatly increased the yield of H3COIn(CH3)2 while the intensities of the CH2O bands were not affected. An extensive set of bands were seen for H3COIn(CH3)2 after irradiation and 18O spectroscopic data was obtained as well. The identification of this species was supported by theoretical calculations at the B3LYP/lanl2dz and B3LYP/dgdzvp levels of theory. Merged jet deposition (longer reaction times) led to high yield of H2CO, CH3OH and C2H6, identifications that were confirmed by 18O substitution. Mechanistic inferences for the initial steps of this reaction are discussed.  相似文献   

14.
A series of nine coordination polymers {[Cd(L)2(solvent)x](solvent)y}n have been prepared from Cd(NO3)2 and 5‐bromonicotinic acid (HL) in different solvents through a layered diffusion method. By using CH3OH/H2O at different volume ratios of 1:1 and 1:3, a one‐dimensional (1D) coordination species ( 1 a ) and a three‐dimensional (3D) (3,6)‐connected framework ( 2 a?g1 ) can be obtained. A similar self‐assembly process in C2H5OH/H2O or H2O/1,4‐dioxane gives 2 a?g2 or 2 a?g3 , which are isomorphic to 2 a?g1 but with different lattice solvents. Replacement of the mixed solvents with DMF/H2O (v/v 1:1 or 1:3) also gives a 1D chain complex ( 1 b ) or a 3D microporous framework ( 2 b?g1 ). Similarly, MOF 2 b?g2 can be assembled from CH3CN/H2O as an isomorphic solvate of 2 b?g1 . Significantly, the 3D MOF families of 2 a?g n and 2 b?g n are supramolecular isomers even though they are topologically equivalent. Also, if a mixture of CH3OH/CH2Cl2 (v/v 1:1 or 3:1) is used, a pair of distinct MOFs ( 3 a?g ) and ( 3 b ) are generated as pseudo‐polymorphs that show a two‐dimensional (2D) sheet and a 3D coordination framework, respectively. Furthermore, mutual solvent‐induced conversions were realized between 1 a and 1 b and between 2 a?g1 , 2 a?g2 , and 2 a?g3 following the size‐dependent rule of the solvent. These results are of great significance in recognizing the solvent effect upon coordination assemblies and their crystal transformations.  相似文献   

15.
Photocatalysis of CH3OH on the ZnO(0001) surface has been investigated by using temperature-programmed desorption (TPD) method with a 266 nm laser light. TPD results show that part of the CH3OH adsorbed on ZnO(0001) surface are in molecular form, while others are dissociated. The thermal reaction products of H2, CH3·, H2O, CO, CH2O, CO2 and CH3OH have been detected. Experiments with the UV laser light indicate that the irradiation can promote the dissociation of CH3OH/CH3O· to form CH2O, which can be future converted to HCOO- during heating or illumination. The reaction between CH3OHZnand OHad can form the H2O molecule at the Zn site. Both temperature and illumination promote the desorption of CH3· from CH3O·. The research provides a new insight into the photocatalytic reaction mechanism of CH3OH on ZnO(0001).  相似文献   

16.
Indirect cathode amination of anisole with Ti(IV)/Ti(III) and NH2OH in media containing 4 or 6 M H2SO4, CH3CN, and H2O (in small amounts) was studied. Para- and ortho-anisidines were the major products of radical cation substitution at 15–45°C. The total yield of monoamino compounds based on the source of amino radicals (with its full conversion) may be up to 84% in these conditions.  相似文献   

17.
Attempts to synthesize solvent‐free MgB12H12 by heating various solvated forms (H2O, NH3, and CH3OH) of the salt failed because of the competition between desolvation and dehydrogenation. This competition has been studied by thermogravimetric analysis (TGA) and temperature‐programmed desorption (TPD). Products were characterized by IR, solution‐ and solid‐state NMR spectroscopy, elemental analysis, and single‐crystal or powder X‐ray diffraction analysis. For hydrated salts, thermal decomposition proceeded in three stages, loss of water to form first hexahydrated then trihydrated, and finally loss of water and hydrogen to form polyhydroxylated complexes. For partially ammoniated salts, two stages of thermal decomposition were observed as ammonia and hydrogen were released with weight loss first of 14 % and then 5.5 %. Thermal decomposition of methanolated salts proceeded through a single step with a total weight loss of 32 % with the release of methanol, methane, and hydrogen. All the gaseous products of thermal decomposition were characterized by using mass spectrometry. Residual solid materials were characterized by solid‐state 11B magic ‐ angle spinning (MAS) NMR spectroscopy and X‐ray powder diffraction analysis by which the molecular structures of hexahydrated and trihydrated complexes were solved. Both hydrogen and dihydrogen bonds were observed in structures of [Mg(H2O)6B12H12] ? 6 H2O and [Mg(CH3OH)6B12H12] ? 6 CH3OH, which were determined by single‐crystal X‐ray diffraction analysis. The structural factors influencing thermal decomposition behavior are identified and discussed. The dependence of dehydrogenation on the formation of dihydrogen bonds may be an important consideration in the design of solid‐state hydrogen storage materials.  相似文献   

18.
The solvolysis of cis(chloro)(1-amino-propan-2-ol)bis(ethylenediamine)cobalt(III) in aqueous alcoholic media using methanol, propan-2-ol, t-butanol as cosolvents, resulted in the formation of the (N,O) chelated productcis[Co(en)2(NH2CH2CHOHCH3)]3+. The pseudo first order rate constant decreased with increasing molfraction (Xorg) of alcohols, the decrease being less marked as the bulkiness of hydrophobic moiety of alcohol increased. The plots of log ??obs vs. reciprocal of the bulk dielectric constant of the solvents, log ??obs vs. Grunwald-Winstein solvent parameter and log ??obs, vs. Xobs under isodielectric condition (Ds = 50, at 50°C) for CH3OH/H2O, C2H5OH/H2O, (CH3)2CHOH/H2O, (CH3)3C? OH/H2O, (CH2)2(OH)2/H2O, and (CH3)2 C ? O/H2O in water rich media indicated that both solvent structural effects and presumably the hydrophobic interaction appreciably mediate the reaction. The calculated values of the relative transfer free energy at 25°C[ΔGt(C3?)-ΔGt(i.s)(sw)] where C3+ and i.s. denote the dissociative transition state {cis[Co(en)2(NH2CH2CHOHCH3)]3+}* and the initial state, respectively, indicated that the tripositive transition state is more effectively solvated by the mixed solvent media, than the dipositive initial state, the effect appeared to be more significant with increasing Xorg. The plots of activation enthalpy and entropy against Xorg exhibited maxima and minima indicating that enthalpy and entropy changes associated with the solvent shell reorganization of the reactant contribute to the overall activation parameters.  相似文献   

19.
The mechanism for the C2H3 + CH3OH reaction has been investigated by the Gaussian‐4 (G4) method based on the geometric parameters of the stationary points optimized at the B3LYP/6–31G(2df, p) level of theory. Four transition states have been identified for the production of C2H4 + CH3O (TSR/P1), C2H4 + CH2OH (TSR/P2), C2H3OH + CH3 (TSR/P3), and C2H3OCH3 + H (TSR/P4) with the corresponding barriers 8.48, 9.25, 37.62, and 34.95 kcal/mol at the G4 level of theory, respectively. The rate constants and branching ratios for the two lower energy H‐abstraction reactions were calculated using canonical variational transition state theory with the Eckart tunneling correction at the temperature range 300–2500 K. The predicted rate constants have been compared with existing literature data, and the uncertainty has been discussed. The branching ratio calculation suggests that the channel producing CH3O is dominant up to about 1070 K, above which the channel producing CH2OH becomes very competitive.  相似文献   

20.
A multicomponent pharmaceutical salt formed by the isoquinoline alkaloid berberine (5,6‐dihydro‐9,10‐dimethoxybenzo[g]‐1,3‐benzodioxolo[5,6‐a]quinolizinium, BBR) and the nonsteroidal anti‐inflammatory drug diclofenac {2‐[2‐(2,6‐dichloroanilino)phenyl]acetic acid, DIC} was discovered. Five solvates of the pharmaceutical salt form were obtained by solid‐form screening. These five multicomponent solvates are the dihydrate (BBR–DIC·2H2O or C20H18NO4+·C14H10Cl2NO2?·2H2O), the dichloromethane hemisolvate dihydrate (BBR–DIC·0.5CH2Cl2·2H2O or C20H18NO4+·C14H10Cl2NO2?·0.5CH2Cl2·2H2O), the ethanol monosolvate (BBR–DIC·C2H5OH or C20H18NO4+·C14H10Cl2NO2?·C2H5OH), the methanol monosolvate (BBR–DIC·CH3OH or C20H18NO4+·C14H10Cl2NO2?·CH3OH) and the methanol disolvate (BBR–DIC·2CH3OH or C20H18NO4+·C14H10Cl2NO2?·2CH3OH), and their crystal structures were determined. All five solvates of BBR–DIC (1:1 molar ratio) were crystallized from different organic solvents. Solvent molecules in a pharmaceutical salt are essential components for the formation of crystalline structures and stabilization of the crystal lattices. These solvates have strong intermolecular O…H hydrogen bonds between the DIC anions and solvent molecules. The intermolecular hydrogen‐bond interactions were visualized by two‐dimensional fingerprint plots. All the multicomponent solvates contained intramolecular N—H…O hydrogen bonds. Various π–π interactions dominate the packing structures of the solvates.  相似文献   

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