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 molecul...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.展开更多
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 f...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.展开更多
Topological indices(TIs)have been practiced for distinct wide-ranging physicochemical applications,especially used to characterize and model the chemical structures of various molecular compounds such as dendrimers,na...Topological indices(TIs)have been practiced for distinct wide-ranging physicochemical applications,especially used to characterize and model the chemical structures of various molecular compounds such as dendrimers,nanotubes and neural networks with respect to their certain properties such as solubility,chemical stability and low cytotoxicity.Dendrimers are prolonged artificially synthesized or amalgamated natural macromolecules with a sequential layer of branches enclosing a central core.A present-day trend in mathematical and computational chemistry is the characterization of molecular structure by applying topological approaches,including numerical graph invariants.Among topological descriptors,Zagreb connection indices(ZCIs)have much importance.This manuscript involves the establishment of general results to calculate ZCIs,namely first ZCI(FZCI),second ZCI(SZCI),third ZCI(TZCI),modified FZCI,modified SZCI and modified TZCI of two special types of dendrimers nanostars,namely,poly propylene imine octamin(PPIO)dendrimer and poly(propyl)ether imine(PPEtIm)dendrimer.Furthermore,we provide the numerical and graphical comparative analysis of our calculated results for both types of dendrimers with each other.展开更多
The novel JX-7 jet fuel desulfurizing agent has been successful tested in commercial scale on the jet fuel hydrotreating unit at the SINOPEC Gaoqiao Branch Company,while delivering a jet fuel with its silver strip cor...The novel JX-7 jet fuel desulfurizing agent has been successful tested in commercial scale on the jet fuel hydrotreating unit at the SINOPEC Gaoqiao Branch Company,while delivering a jet fuel with its silver strip corrosion indicator meeting the military jet fuel standard.展开更多
The theory of networks provides a mathematical basis for building and model-ing the chemical structures and complex networks.Topological indices(TIs)are employed in several physicochemical applications,particularly fo...The theory of networks provides a mathematical basis for building and model-ing the chemical structures and complex networks.Topological indices(TIs)are employed in several physicochemical applications,particularly for characteriz-ing and modeling the chemical structures of diverse molecular compounds,in-cluding dendrimers.Dendrimers are intentionally synthesized or combined nat-ural macromolecules characterized by a series of branching layers around a cen-tral core.In this manuscript,we calculate various connection-based Zagreb in-dices(ZIs),including the atom-bond connectivity connection index(ABCCI),geometric-arithmetic connection index(GACI),augmented connection index(ACI),symmetric division connection index(SDCI),harmonic connection in-dex(HCI),inverse sum connection index(ISCI),and hyper Zagreb connection index(HZCI).Additionally,we discuss the connection-based ZIs for one of the most significant types of dendrimers,namely Tetrathiafulvalene(TTF)den-drimers.In addition,we provide a detailed numerical and graphical compara-tive analysis of the calculated results for TTF dendrimers,highlighting their per-formance and potential advantages in various applications.展开更多
文摘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.
文摘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.
文摘Topological indices(TIs)have been practiced for distinct wide-ranging physicochemical applications,especially used to characterize and model the chemical structures of various molecular compounds such as dendrimers,nanotubes and neural networks with respect to their certain properties such as solubility,chemical stability and low cytotoxicity.Dendrimers are prolonged artificially synthesized or amalgamated natural macromolecules with a sequential layer of branches enclosing a central core.A present-day trend in mathematical and computational chemistry is the characterization of molecular structure by applying topological approaches,including numerical graph invariants.Among topological descriptors,Zagreb connection indices(ZCIs)have much importance.This manuscript involves the establishment of general results to calculate ZCIs,namely first ZCI(FZCI),second ZCI(SZCI),third ZCI(TZCI),modified FZCI,modified SZCI and modified TZCI of two special types of dendrimers nanostars,namely,poly propylene imine octamin(PPIO)dendrimer and poly(propyl)ether imine(PPEtIm)dendrimer.Furthermore,we provide the numerical and graphical comparative analysis of our calculated results for both types of dendrimers with each other.
文摘The novel JX-7 jet fuel desulfurizing agent has been successful tested in commercial scale on the jet fuel hydrotreating unit at the SINOPEC Gaoqiao Branch Company,while delivering a jet fuel with its silver strip corrosion indicator meeting the military jet fuel standard.
文摘The theory of networks provides a mathematical basis for building and model-ing the chemical structures and complex networks.Topological indices(TIs)are employed in several physicochemical applications,particularly for characteriz-ing and modeling the chemical structures of diverse molecular compounds,in-cluding dendrimers.Dendrimers are intentionally synthesized or combined nat-ural macromolecules characterized by a series of branching layers around a cen-tral core.In this manuscript,we calculate various connection-based Zagreb in-dices(ZIs),including the atom-bond connectivity connection index(ABCCI),geometric-arithmetic connection index(GACI),augmented connection index(ACI),symmetric division connection index(SDCI),harmonic connection in-dex(HCI),inverse sum connection index(ISCI),and hyper Zagreb connection index(HZCI).Additionally,we discuss the connection-based ZIs for one of the most significant types of dendrimers,namely Tetrathiafulvalene(TTF)den-drimers.In addition,we provide a detailed numerical and graphical compara-tive analysis of the calculated results for TTF dendrimers,highlighting their per-formance and potential advantages in various applications.
