A Quantitative Structure Property Relationship for Prediction of Flash Point of Alkanes Using Molecular Connectivity Indices

Many structure-property/activity studies use graph theoretical indices, which are based on the topological properties of a molecule viewed as a graph. Since topological indices can be derived directly from the molecular structure without any experimental effort, they provide a simple and straightforward method for property prediction. In this work the flash point of alkanes was modeled by a set of molecular connectivity indices （Х）, modified molecular connectivity indices （ ^mХ^v ） and valance molecular connectivity indices （ ^mХ^v ）, with ^mХ^v calculated using the hydrogen perturbation. A stepwise Multiple Linear Regression （MLR） method was used to select the best indices. The predicted flash points are in good agreement with the experimental data, with the average absolute deviation 4.3 K.

Prediction of aqueous solubility of PCBs based on molecular structure

The thermodynamic relationships among aqueous solubility and molar volume (MV) , total molecular surface area (TSA) and molecular connectivity index (MCI) for highly hydrophobic chemicals. PCBs are established and discussed, respectively. Good linear relationships exist among In Cs and MV, TSA or MCI.

Parallel Molecular Dynamics on the Connection Machines

Abstract Abstract:We have demonstrated using vectorized parallel Lennard-Jones fluid program that vectorizing general-purpose parallel molecular package for simulating biomolecules which currently runs on the Connection Machine CM-5 using CMMD message passing would offer a significant improvement over 4 non-vectorized version. Our results indicate that the Lennard-Jones fluid program written in C*/CMNID is five times faster than the same program written in C/CMMD.

A Modifi ed Molecular Structure Mechanics Method for Analysis of Graphene

Based on molecular mechanics and the deformation characteristics of the atomic lattice structure of graphene, a modifi ed molecular structure mechanics method was developed to improve the original one, that is, the semi-rigid connections were used to model the bond angle variations between the C-Cbonds in graphene. The simulated results show that the equivalent space frame model with semi-rigid connections for graphene proposed in this article is a simple, efficient, and accurate model to evaluate the equivalent elastic properties of graphene. Though the present computational model of the semi-rigid connected space frame is only applied to characterize the mechanical behaviors of the space lattices of graphene, it has more potential applications in the static and dynamic analyses of graphene and other nanomaterials.

Predicting physico-chemical properties of polychlorinated diphenyl ethers (PCDEs): potential persistent organic pollutants(POPs)

Polychlorinated diphenyl ethers(PCDEs) have received more and more concerns as a category of potential persistent organic pollutants(POPs). Modeling its environmental fate and exposure assessment require a number of fundamental physico-chemical properties. However, the experimental data are currently limited due to the difficulty in analysis caused by the complexity of PCDE congeners. As an alternative, the quantitative structure property relationship(QSPR) approach could be used. In this paper, twelve kinds of molecular connectivity indices(MCIs) of all 209 possible molecular structure patterns of PCDEs were calculated. Based on 106 PCDEs with three observed physico-chemical properties—vapour pressure(P 0 L), aqueous solubility(S w) and n-octanol/water(K ow ) and their MCIs data, a series of QSPR equations were established using multiple linear regression(MLR) method. As a result, three equations with best performance were selected mainly from the view of high regression coefficient(R) and low standard error(SE). All of them showed significant relationship and high accuracy. With these equations the properties of other 103 patterns of PCDEs without the reported observed values were predicted. Furthermore, three partition properties for PCDE congeners—Henry's Law constants(H), partition coefficients between gas/water(K gw ) and gas/n-octanol(K go ) were calculated according to the internal relationship among these six properties. These observed and predicted values, in contrast with the criteria listed in the Stockholm treaty about POPs which has been signed by more than ninety countries in May 2001, illustrated that most of PCDEs congeners are potential persistent organic pollutants. As all descriptors/predictors are derived just from the molecular structure itself and without the import of any empirical parameters, this method is impersonal and promising for the estimation of physico-chemical properties of PCDEs.

Condensed Extended Hyper-Wiener Index

According to the definitions of molecular connectivity and hyper-Wiener index, a novel set of hyper-Wiener indexes （Dn, ^mDn） were defined and named as condensed extended hyper-Wiener index, the potential usefulness of which in QSAR/QSPR is evaluated by its correlation with a number of C3-C8 alkanes as well as by a favorable comparison with models based on molecular connectivity index and overall Wiener index.

QSPR Analysis of the Physicochemical Properties for Phthalic Acid Esters

Based on quantitative structure-property relationship （QSPR） of organic compounds, the molecular connectivity indices of 21 phthalic acid ester compounds were extracted. Relationship between the physicochemical properties （n-octanol/air partition coefficient, vapor pressure, water solubility） and the molecular connectivity indices of phthalic acid ester compounds have been established by multiple linear regression （MLR） method. The results showed that the zero-order valence connectivity index （0Xu） is the topology parameter which affects octanol/water partition coefficient and water solubility, and the topology parameter which affects vapor pressure is the first-order connectivity index （1X）. This indicated to a certain extent_that the molecular connectivity indices can be well used to express the quantitative relationship between the physicochemical properties and structure descriptions of phthalic acid ester compounds. The models constructed have good robustness and highly predictive capability.

Application of Connection in Molecular Dynamics

The evolution of electronic states in molecule has two origins: dynamical one produced by Schr¨odinger equation and kinematical one caused by base transformation due to nuclear motion.In current theories,the former gets analytic expression; the latter depends on heavy numerical calculation,which contains uncertainty.By using connection of fiber bundles,this paper establishes an analytic formula for the latter,and the numerical work is simplified.It shows the mathematical structure of molecule is fiber bundle.