Zhengting Cai

Mesoscopic simulation study on phase diagram of the system oil/water/aerosol OT

A simple model, i.e., sodium bis(2-ethylhexyl) sulfosuccinate (AOT) represented by one-head and two-tail beads tied together by a harmonic spring and water or iso-octane by one bead, was put forward via dissipative particles dynamics (DPD) simulation method. Using the changes of interfacial tension between water and oil phase, a ternary phase diagram of AOT/water/iso-octane system was drawn.

Theoretical investigations of the H···π and X (X = F, Cl, Br, I)···π complexes between hypohalous acids and benzene

The H···π and X (X = F, Cl, Br, I)···π interactions between hypohalous acids and benzene are investigated at the MP2/6-311++G(2d,2p) level. Four hydrogen-bonded and three halogen-bonded complexes were obtained. Ab initio calculations indicate that the X···π interaction between HOX and C6H6 is mainly electrostatically driven, and there is nearly an equal contribution from both electrostatic and dispersive energies in the case of XOH–C6H6 complexes. Natural bond orbital (NBO) analysis reveals that there exists charge transfer from benzene to hypohalous acids. Atom in molecules (AIM) analysis locates bond critical points (BCP) linking the hydrogen or halogen atom and carbon atom in benzene.

Quantitative Structure–Property Relationships of Surfactants: Critical Micelle Concentration of Anionic Surfactants

ABSTRACT A quantitative structure–property relationship (QSPR) was used to predict the critical micelle concentration (cmc) of anionic surfactant in aqueous solution. Some conformational, electronic, spatial and thermodynamic properties were selected as descriptors to build a relationship between the macro-property (such as the cmc) and the micro-structures. These descriptors include the octanol/water partition coefficient, the total area of surfactant molecule and the dipole moment of the surfactant molecule. A general four-parameter structure-property relationship between the logarithm of cmc and the descriptors, which was developed for a set of 37 anionic surfactants of sodium alkyl sulfates (r 2=0.996, F-test=1838.773), can be used to predict the cmc of anionic surfactants.

Molecular simulation study of alkyl monolayers on the Si(111) surface

The structure of eight-carbon monolayers on the H-terminated Si(111) surface was investigated by a molecular simulation method. Molecular mechanics calculations showed that the best substitution percentages on the Si(111) surface were 50% for octene or octyne-derived monolayers and 40% for the styrene or phenylacetylene-derived monolayers. These values are in good agreement with the experimental results. After a two-dimensional cell containing alkyl chains and four layers of Si atoms was constructed, the densely packed and well-ordered monolayer on the Si(111) surface can be shown at the molecular level. At the same time, the thickness of the monolayers and the tilt angle of the alkyl chain were also calculated. Additionally, the theoretical calculations showed that the CC bond of the alkyne only reacts once with the H-terminated Si(111) surface, that is only one Si–C bond per organic molecule is formed on the Si(111) surface, which verifies the experimental results. It is thus shown that molecular simulation can provide otherwise inaccessible microscopic information at the molecular level, and may be considered as a useful adjunct to experiments.

Quantum chemical study of alcoholysis mechanism of 1,2-thiazetidine 1,1-dioxide

The alcoholysis of 1,2-thiazetidine 1,1-dioxide has been investigated using ab initio and density functional theory at HF/6-31G*, MP2/6-31G*//HF/6-31G* and B3LYP/6- 31G* levels. The geometries, energies and frequencies of all stationary points were calculated in detail. Solvent effects have been considered by means of a polarizable continuum model (PCM). Our results indicate the alcoholysis of 1,2-thiazetidine 1,1-dioxide proceeds via concerted mechanism and stepwise mechanism. In the stepwise mechanism, two possible reaction pathways can be followed whilst one possible reaction pathway can be followed in the concerted mechanism. The most favorite pathway for alcoholysis of 1,2-thiazetidine 1,1-dioxide was found.

THEORETICAL STUDY ON PARTIAL POTENTIAL SURFACE AND SCATTERING RESONANCE STATE OF THE ASYMMETRICAL H EXCHANGING X + H2O → XH + OH (X = Cl, F, H) REACTIVE SYSTEM

In the course of an extensive investigation aimed at understanding the detailed mechanism of a prototypical polyatomic reaction, several remarkable observations were uncovered. To interpret these findings, we surmise the existence of a reactive resonance in this polyatomic reaction. The system of concern is X + H2O → XH + OH (X = Cl, F, H), and it belongs to a type of asymmetrical H exchanging reaction. Because the concerned electronic number is quite small, it is usually regarded as a template constructed the model of theory or experiment. In this paper, compared with the symmetrical systems, we constructed the partial potential surfaces of asymmetrical systems in order to research their resonance states. All results are in good agreement with previous theoretical and experimental works.

THE PARTIAL POTENTIAL ENERGY SURFACE AND SCATTERING RESONANCE STATE OF THE STATE-TO-STATE REACTION Br + HBr(v) → BrH(v′) + Br

In this paper, the partial potential energy surface (PPESs) of the Br + HBr and Br- + HBr systems including the minimum energy path and the vibrational potential curves were constructed at MP2/6-311++G** level, based on the conception and constructing approach of the PPESs previously proposed. These results obtained from the PPESs were compared with those from the high resolved threshold photodetachment spectrum of the BrHBr- anion measured by Neumark et al., J Phys Chem94, 1377–1388, 1990. On the basis of the PPESs, the scattering resonance states of the Br + HBr(v) → BrH(v′) + Br state-to-state reaction were studied and the satisfactory results were obtained. Subsequently, we calculated the width and lifetime of the resonance states in this reaction by the one-dimensional square potential well model, and obtained some results consistent to the experiments.

Scattering Resonance State of Br+HBr( v =0)→BrH( v ’=0)+Br Reaction Explored by Partial Potential Energy Surface Method

The partial potential energy surface(PPES) of Br+HBr(v=0)→BrH(v′=0)+Br was designed by coupling the vibration energy and the minimum energy of the corresponding reaction path, Vmep. All the calculations were performed at the theoritical level of QCISD(T)/6-311++G**//MP2/6-311++G**. Based on the analysis of PPES, the dynamic “Eyring Lake” mechanism gave birth to the scattering resonance state. The resonance energy was also obtained via PPES. Then a lifetime matrix of the resonance state was established by solving the translational wave-function via the numerical propagation method. Then the reaction resonance lifetime was calculated to be 125 fs. It is in good agreement with the experimental result.

THEORETICAL STUDY ON HYDROLYSIS MECHANISM OF β-PHOSPHOLACTAMS

The neutral hydrolysis mechanisms of a simple β-phospholactam with and without water-assisted reaction have been studied by using quantum chemical method at HF/6-31G**, MP2/6-31G** and B3LYP/6-31G** levels, respectively. The reaction can proceed by two different mechanisms: concerted and stepwise. There are two pathways in stepwise, i.e. pathway a and b, and the energy barriers of them are close. The energy barriers of water-assisted hydrolysis of β-phospholactam are obviously lower than those of no-water-assisted hydrolysis system. The energy barriers of stepwise mechanism are much lower than those of the concerted pathway in both cases. The solvent effects have been considered by means of a polarizable continuum model. The hydrolysis mechanism of β-phospholactam with that of the β-lactam and β-sultam was compared.

REACTIVE RESONANCE AND FORMATION MECHANISM STUDIES OF THE H + NO → N + OH OR O + NH REACTION

The partial potential energy surface (PPES) of H + NO → N + OH or O + NH of 3A″ symmetry is first constructed using QCISD (T) method with 6-311++g** basis set, and then we speculate the existence of the scattering resonance states of these reactions. Finally, we estimate that the lifetime of scattering resonance state is about 1.5 ps, which is in agreement with Schatzs conclusion (~1.2 ps). The scattering resonance states of the two reactions belong to the Feshbach type. The results are consistent with the probabilities calculations reported in the literatures.