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1.
采用量子化学从头算方法在HF/6-31G(d)水平上对氯磺隆、甲嘧磺隆和氟嘧磺隆三种典型的磺酰脲类除草剂在酸性和中性条件下水解反应的机理进行理论研究,分别优化了各反应途径中反应物、过渡态、中间体以及产物的几何构型,并通过振动分析确定反应的过渡态和中间体的真实性。同时,在B3LYP/6-31G(d)水平上计算各驻点的单点能,以及溶剂效应对水解反应的影响。从能量上看,酸性条件更有利于水解反应的进行,与实验结果较为吻合. 相似文献
2.
DFT computations have been performed in acetone and water solvents in order to investigate the mechanism of hydrolysis of acid chlorides. Acetyl chloride and chloroacetyl chloride hydrolyze via concerted, one‐step SN2 mechanism, with the attack of water at the sp2 hybridized carbon atom of the C?O group, and the transition state (TS) has distorted tetrahedral geometry. Solvent molecules act as general base and general acid catalysts. The TS of chloroacetyl chloride is tighter and less polar than the TS of acetyl chloride. The structure of the SN2 TS for the hydrolysis of benzoyl chlorides changes with the substituents and the solvent. Tight and loose TSs are formed for substrates bearing electron withdrawing (e‐w) and electron donating (e‐d) groups, respectively. In acetone, only the e‐w effect of the substituents increase the reactivity of the substrates, and the change of the structure of the TSs with the substituents is small. In water, polar and very loose TSs are formed in the reactions of benzoyl chlorides bearing e‐d substituents, and the rate enhancing effect of both e‐d and e‐w groups can be computed at higher level of theory. Calculated reactivities and the changes of the structure of the TSs with substituents and solvent are in accordance with the results of kinetic studies. In SN2 nucleophilic substitutions late/early TSs are formed if the attacking reagent is poorer/better nucleophile than the leaving group, and loose/tight TSs are formed for substrates bearing e‐d/e‐w substituents and in protic/aprotic solvents. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
3.
Takao Okazaki Gaku Aoyama Toshikazu Kitagawa 《Journal of Physical Organic Chemistry》2021,34(1):e4129
Reactions of 5‐R‐1‐indanones (R = Me, t‐Bu, Cl, F) in ionic liquids in the presence of Brønsted acid afforded substituted truxenes as aldol cyclotrimerization products, whose yields were found to be better in [BMIM][Tf2N] than in [BMIM][BF4]. Their cyclotrimerizations were slower and gave lower yields than that of the parent 1‐indanone. Furthermore, the reaction mixtures contained some amounts of intermediate products, 5‐R‐2‐(5‐R‐1‐indanylidene)‐1‐indanone, formed by the initial aldol condensation. These results suggested that both the electron‐donating and the electron‐withdrawing substituents at the C(5) position reduced the rate of cyclotrimerization. This rate retardation was supported by DFT/B3LYP calculations with the PCM solvation model. The activation energies of the reaction of the protonated indanones and the indenols in the initial aldol condensation were increased by both the electron‐donating group (EDG) and the electron‐withdrawing group (EWG). The transition states in the second aldol condensation and in the electron‐cyclization were also destabilized by both the EDG and the EWG. 相似文献
4.
A novel fluorescent switchable chemosensor 1 , which is composed of an anthracene‐modified calix[4]crown in the 1,3‐alternate conformation, was calculated by density functional theory and time‐dependent density functional theory method. Geometries, molecular orbitals and binding thermal energies were evaluated at the restricted hybrid Becke's three‐parameter exchange functional using 6‐31 G(d) basis set and relativistic effective core potentials. The metal–ligand and cation–π interactions were investigated acting as two main types of driving force. Our calculations clearly show that solvent effects strongly influence cation selectivity, and K+ selectivity is recovered when even a few waters of hydration are considered. The calculations indicate that because of the photoinduced electron transfer effect, the addition of alkali metal ions have hardly any effect on the fluorescence of ligand 1 under neutral or basic conditions. Also, the high selectivity of ligand 1 for K+ and Rb+, under acidic conditions, the complexed metal ion can result in ammonium ion deprotonation, which leads to quenching of fluorescence of 1 •H+. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
5.
Hatchootah Ashish 《Molecular physics》2013,111(1):175-185
This work aims to study the trans and cis conformers of furfural, thiofurfural and selenofurfural in the gas and solution phases. Assuming that there is equilibrium between these conformers, the transition state has also been investigated. All computations have been done using density functional theory method with B3LYP as the functional and 6-311++G(d,p) as the basis sets. The optimized molecular structures and related parameters of these conformers are reported. The infrared wavenumbers and Raman activities of these conformers are also reported with appropriate assignments. The energy differences between the trans and cis conformers, associated barriers and thermodynamical parameters have been derived from the computations. It is found that the structural parameters are not much different in the gas and solution phases. However, in the gas phase, the trans conformer is always more stable, but increasing the polarity of the solvent leads to the cis conformer becoming more stable. The rotational barrier is always larger than the energy difference and both of them increase when the solvent becomes more polar. Some of the results for furfural compare satisfactorily with literature and therefore the data from this work will be useful for thiofurfuraldehyde and selenofurfuraldehyde, as their literature is limited. 相似文献
6.
Moira K. Ridley Hans Lischka Daniel Tunega Adelia J.A. Aquino 《Molecular physics》2019,117(9-12):1507-1518
7.
The [4 + 2] cycloadditions of singlet oxygen to 9,10‐diphenylanthracene ( 1 ) and the meta and para isomers of 9,10‐dipyridylanthracene ( 2m / p ) and 9,10‐methoxyphenylanthracene ( 3m / p ) have been studied by density functional calculations in the gas phase at the UB3LYP/6‐31G* level and for the first time in solvents at the conductor‐like polarizable continuum model (CPCM) UM062X/6‐31G* level. The differences in calculated transition state (TS) energies derived from this method are in line with experimentally observed reactivity orders in solution. For the gas‐phase reaction, the first TS of the stepwise pathway ( TS1 ) has biradical character, and its energy lies below the energy of the TS of the concerted path ( TS conc ). In contrast, in the solvent acetonitrile, TS1 resembles a zwitterion and lies significantly higher than the TS conc . Thus, a concerted mechanism applies in solvents, and the energy gap between the TS of the two processes decreases with decreasing polarity. A change from a pyridyl against a methoxyphenyl substituent in the para position causes a maximal reduction of the activation barrier by approximately 1.7 kcal/mol, resulting in a fivefold increased reactivity. 相似文献
8.
Ali Reza Harifi‐Mood Aziz Habibi‐Yangjeh Mohammad Reza Gholami 《Journal of Physical Organic Chemistry》2008,21(9):783-788
The second‐order rate constants for cycloaddition reaction of cyclopentadiene with naphthoquinone were determined spectrophotometrically in various compositions of 1‐(1‐butyl)‐3‐methylimidazolium terafluoroborate ([bmim]BF4) with water and methanol at 25 °C. Rate constants of the reaction in pure solvents are in the order of water > [bmim]BF4 > methanol. Rate constants of the reaction decrease sharply with mole fraction of the ionic liquid in aqueous solutions and increase slightly to a maximum in alcoholic mixtures. Multi‐parameter correlation of logk2 versus solute–solvent interaction parameters demonstrated that solvophobicity parameter (Sp), hydrogen‐bond donor acidity (α) and hydrogen‐bond acceptor basicity (β) of media are the main factors influencing the reaction rate constant. The proposed three‐parameter model shows that the reaction rate constant increases with Sp, α and β parameters. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
9.
Han‐Yuan Lin Eddy Lay Wen‐Yen Wen Hamza Dewi Yu‐Chi Cheng Shau‐Wei Tsai 《Journal of Physical Organic Chemistry》2004,17(5):387-392
By using strong neutral bases as catalyst, a detailed investigation of the racemization of (S)‐naproxen 2,2,2‐trifluoroethyl ester was conducted in the non‐polar solvents isooctane, cyclohexane and n‐hexane. The second‐order interconversion constant as representing the ion‐pair kinetic basicity in isooctane was first estimated and correlated with the equilibrium ion‐pair basicity pKip in tetrahydrofuran, giving slopes of 0.768 and 0.689 for non‐phosphazene and phosphazene bases, respectively, in the Brønsted correlations. The result was further compared with that for (S)‐naproxen 2,2,2‐trifluoroethyl thioester, showing about a 1–2 orders of magnitude enhancement of for the corresponding thio‐containing analogue. A smaller influence of non‐polar solvents (i.e. isooctane, n‐hexane and cyclohexane) on was found. Kinetic analysis of the racemization and hydrolysis of (S)‐naproxen 2,2,2‐trifluoroethyl ester in isooctane and n‐hexane containing 7‐methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene and water suggests nucleophilic hydrolysis by the base, where the breakdown of tetrahedral intermediates IR1 and IS1 is the rate‐limiting step and the hydrolysis constant khy is in proportion to the product of base and ion‐pair concentrations. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
10.
Aromatic nucleophilic substitution reaction of 1‐fluoro‐2,4‐dinitrobenzene with piperidine was kinetically investigated in ethylene glycol‐choline chloride and glycerol‐choline chloride as 2 deep eutectic solvents (DESs) mixed with dimethyl sulfoxide, in whole mole fractions, at room temperature. The investigation of the reaction in different concentrations of the piperidine shows that the reaction follows the base‐catalyzed mechanism. The measured rate coefficients of the reaction demonstrated a sharp decreasing in all mixtures with the increasing mole fraction of DESs. Linear free energy relationship investigations confirm that hydrogen bond donor ability in addition to polarity‐polarizability of the media has a major effect on the reaction rate. The decrease in the rate coefficient is attributed to not only hydrogen‐bonding donor interactions of the media with piperidine as both reactant and catalyst but also the preferential solvation of reactants by DES compared with the intermediate of the reaction. 相似文献
11.
荧光核酸碱基类似物的设计合成是众多研究领域的热点课题. 本文利用密度泛函理论(DFT)和含时密度泛函理论(TDDFT)考察了新型鸟嘌呤类似物y-鸟嘌呤(yG-t1) 及其五个异构体(yG-t2到yG-t6)的结构性质、电子性质和光谱性质, 同时考察了甲醇溶剂和碱基配对对其光谱性质的影响. 研究表明, 气相中y-鸟嘌呤的标准结构并不是最稳定的结构, 其具有三个能量相近的异构体, y-鸟嘌呤最有可能以这三种形式存在. 光谱性质研究表明y-鸟嘌呤的最大吸收波长比天然鸟嘌呤大得多, 人们可以对其进行选择性激发. y- 鸟嘌呤的标准结构与其异构体显示出不同的光谱特性, 因此可以利用其电子光谱指纹对它们进行区分. 研究发现甲醇溶剂将使y-鸟嘌呤标准结构的最大吸收波长和荧光发生蓝移, 而使其他异构体相应值发生红移; 与胞嘧啶配对将使yG-t1, yG-t2, yG-t5 和yG-t6的最大吸收波长和荧光波长发生蓝移, 表明y-鸟嘌呤的电子光谱性质受环境影响较大. 相似文献
12.
Gulnara G. Iskhakova Vladimir D. Kiselev Rudi van Eldik Achim Zahl Mehdi S. Shihab Alexander I. Konovalov 《Journal of Physical Organic Chemistry》2011,24(5):360-365
Solvent, salt and high pressure effects on the rate and equilibrium constants for the formation of tri‐n‐butylphosphoniumdithiocarboxylate at 298.2 K are reported. This equilibrium is shifted to the phosphobetaine in polar solvents, salt solutions and under high external pressure. The reaction volume changes dramatically on going from less polar diethyl ether (−69 cm3 mol−1) and tetrahydrofurane (THF) (−66 cm3 mol−1), to more polar acetonitrile (−39 cm3 mol−1) and acetone (−38 cm3 mol−1). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
13.
Hang Chen Lu Jia Xuan Xu Jianyong Mao Yong Wang Congmin Wang Haoran Li 《Journal of Physical Organic Chemistry》2013,26(6):460-466
For conventional organic substituents, an almost linear relationship can be established between the para Hammett constants in aqueous solutions and chemical shifts or natural population analysis charges (NPA charges). Based on these correlations, the Hammett constants of six synthesized ionic‐pair substituents were estimated via the chemical shifts, which were well in agreement with the results calculated by NPA charges. The para Hammett constants of 89 different ionic‐pair substituents (77 anion‐cationic and 12 cation‐anionic) were therefore calculated in the gas phase based on the density functional theory method. The results show that both the anion‐cationic and cation‐anionic substituents are electron‐withdrawing groups and the different cation–anion combinations could tune the Hammett constants of the ionic‐pair substituents in a range from 0.03 to 0.77. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
14.
基于苯溶剂化效应的多种邻苯二甲酸酯(PAEs)拉曼特征振动光谱辨识 总被引:1,自引:1,他引:0
利用密度泛函与自洽反应场理论在B3LYP/6-311G(d)水平下对16种邻苯二甲酸酯(PAEs)进行结构优化,并计算气态环境及溶剂中PAEs的拉曼光谱振动频率和去偏振度.研究显示,16种PAEs拉曼振动归属为苯环变形、酯基振动、C-C伸缩、C-H摇摆、C-H伸缩与耦合振动.其中酯基官能团出峰位置在1700~1780cm-1之间,拉曼峰较强,去偏振度较低(振动的对称性较强),可将酯基振动作为特征振动;但气态环境下仅12种PAEs拉曼峰之间的最小波数差大于显微拉曼光谱仪的检出限(0.2cm-1),即利用酯基频区的去偏振度和拉曼峰不能完全辨识16种PAEs.溶剂化效应分析显示,溶剂苯对16种PAEs具有明显的溶剂化增强效应,16种PAEs拉曼峰之间最小波数差均增大到0.2cm-1以上,且峰强增加了23%~183%,说明溶剂化效应下可利用酯基频区的去偏振度和拉曼峰辨识16种PAEs.本文的研究结果为PAEs拉曼光谱检测提供了理论依据. 相似文献
15.
Birendra Kumar Deepti Tikariha Kallol K. Ghosh Nadia Barbero Pierluigi Quagliotto 《Journal of Physical Organic Chemistry》2013,26(8):626-631
Kinetic study has been performed to understand the reactivity of novel cationic gemini surfactants viz. alkanediyl‐α,ω‐bis(hydroxyethylmethylhexadecylammonium bromide) C16‐s‐C16 MEA, 2Br− (where s = 4, 6) in the cleavage of p‐nitrophenyl benzoate (PNPB). Novel cationic gemini C16‐s‐C16 MEA, 2Br− surfactants are efficient in promoting PNPB cleavage in presence of butane 2,3‐dione monoximate and N‐phenylbenzohydroxamate ions. Model calculation revealed that the higher catalytic effect of ethanol moiety of gemini surfactants (C16H33N+ C2H4OH CH3 (CH2)S N+ C2H4OH CH3C16H33, 2Br−, s = 4, 6) is due to their higher binding capacity toward substrate. This is in line with finding that binding constants for novel series of cationic gemini surfactants are higher than conventional cationic gemini (C16H33N+(CH3)2(CH2)SN+(CH3)2C16H33, 2Br−, s = 10, 12), cetyldimethylethanolammonium bromide and zwitterionic surfactants, i.e. CnH2n+1N+Me2 (CH2)3 SO3− (n = 10; SB3‐10). The fitting of kinetic data was analyzed by the pseudophase model. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
16.
Giorgio Cevasco Andrea Galatini Necmettin Pirinççioğlu Sergio Thea Andrew Williams 《Journal of Physical Organic Chemistry》2008,21(6):498-504
The host molecule octacarboxymethyl calix[4]resorcinarene 1 catalyses the hydrolysis of substituted phenyl N‐methylpyridinium‐4‐carboxylate esters 3a–f by complexation followed by intracomplex reaction via an anhydride intermediate. The reactivity in the presence of 1 is higher than that of the background at low pH; at high pH an inversion of reactivity occurs, the background becomes predominant since the host inhibits hydrolysis of the esters. The reactivity of esters 3a–f complexed with the host suffers little change in effective charge on the phenolic oxygen (?0.15 units) in contrast with the changes observed in alkaline hydrolysis (?0.28 units) and in the hydrolysis of the model monoaryl glutarate esters (‐1.02 units). The less negative effective charge in the transition state for host 1 catalysis compared with that in the glutarate case is ascribed to stronger solvation by water molecules in the complex compared with that due to water molecules in the bulk solvent. 相似文献
17.
Ji‐Cai Fan Zhi‐Cai Shang Jun Liang Xiu‐Hong Liu Yang Liu 《Journal of Physical Organic Chemistry》2008,21(11):945-953
Oxidation of aliphatic and aromatic alcohols has been studied by using N‐bromosuccinimide (NBS) as oxidant and polyethylene glycol (PEG) as reaction medium under mild reaction conditions. Temperature and solvent effect are studied. Theoretical study is also done with the Gaussian 98 suite of program and the calculation results are in good accordance with the experimental outcome. This system offers a very clean, convenient, environmentally benign method for the oxidation of alcohols. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
18.
Morteza Rouhani 《Journal of Physical Organic Chemistry》2020,33(11):e4106
The effect of substitution, solvent, and temperature on Mumm rearrangement has been investigated using density functional theory (DFT). A potential energy surface (PES) profiles of transition state (TS) is demonstrated to illustrate the alteration of ΔG‡ of Mumm rearrangements for various substitutions. The possible reasons have been studied for the impressive conditions needed for Mumm rearrangement. 相似文献
19.
Using DFT SCRF calculations, we have evaluated the solvent effects on the structure, stability, and electronic properties of biologically active compounds as (E)‐3‐X‐indoline‐2‐one derivatives (X = phenyl, furan‐2‐yl, 1H‐pyrrol‐2‐yl, and thiophen‐2‐yl, I‐IV , respectively) in six solvents. These solvents differ in their polarity with the dielectric constants varying from 2.2 to 78.5 including benzene, C2H4Cl2, EtOH, H2O, nitromethane, and DMSO. Moreover, two of them have a hydrogen‐bond donor character. All possible hydrogen‐bonding in the water solution with oxygen and nitrogen atoms as hydrogen‐acceptor centers in indoline‐2‐ones derivatives, I‐IV , have been considered in our studies. The stability of each solute ( I ‐ IV ) depends on the dielectric constant of the solvent and the possibility of the hydrogen bonding. Moreover, the highest observed solvent‐gas phase energy gaps (∆Es‐g) relate to structure III in water, whereas the lowest ∆Es‐g is associated with II in benzene. Thus, III is the most solvent sensitive and enjoys maximum stabilization in water. On the other extreme, II is the least solvent sensitive, and its stability is the least affected by salvation in benzene. Forbidden concerted [1,6] and [1,3]‐H shift mechanisms are suggested for the ketone III ― III′ , III′′ enole tautomerizations in gas phase, while allowed step‐by‐step [1,6] and [1,3]‐H shifts are proposed for tautomerization in water. 相似文献
20.
David Cáceres-Castillo Gonzalo J. Mena-Rejón Carolina S. Castro-Segura 《Molecular physics》2020,118(6)
A theoretical mechanistic investigation of the cycloaddition reaction of quercetine with 3,5-di-tert-butyl-o-quinone has been carry out employing density functional calculations at M06-2X/6-31G(d,p) level of theory. This computational study was performed in order to gain insight in the energetic and structural parameters that rule the observed experimental selectivity in the synthetised cyclodimers obtained under classical heating and microwave irradiation conditions and the influence of the solvent on their chemical reactivity. The effect of the solvent in the selectivity was studied implicitly using the polarisable continuum model in absence and presence of one explicit solvent’s molecule. The theoretical results explain the main issues of the classical heating and the MWI reaction and suggest that thermal effects are directly responsible for the reaction selectivity observed. The comparison of the mechanistic pathway and the non-covalent interactions, shows that a dioxane assisted mechanism can explain the observed experimental selectivity of the two synthetised compounds, thus the dioxane molecule play a catalytic role on this hetero Diels–Alder reaction. 相似文献