Structure-activity relationships of oxime compounds as flotation collectors by DFT calculations

The relationships between the structure of oxime compounds(R^(1)R^(2)C=NOH,R^(1)/R^(2)=alkyl groups) with different substituents and their corresponding flotation performances were studied. The analyses of density functional theory(DFT) calculations illustrated that the introduced phenyl group at the R^(1) position could enhance the acidity,while the heptyl group could effectively increase the hydrophobicity and benefit van der Waals interactions. Meanwhile,the introduced amino group at the R^(2) position could provide cationic sites to interact with negatively charged surfaces of minerals, while the introduced hydroxyl group could provide additional action sites to form stable chelates with metal ions. Based on the structure-activity relationships, structural optimization was carried out to obtain three efficient collectors, which possessed superior flotation separation performances, proving the effectiveness of the structural modification to oxime compounds in this work.

On QSAR Study of Stereoselectivity for Wittig Reaction

Molecular structures of reactants were characterized by molecular electronegativity distance vector （VHMED） considering hydrogen association. A reasonable molecular modeling equation with 4-parameters was achieved for quantitative structure-property/activity relationship （QSPR/QSAR） by stepwise multiple regression （SMR） that the variable was introduced item by item in significant level order. A high correlation coefficient （R = 0.980） demonstrates that the model is able to well express a quantitative relation between stereoselectivity and the reactant structures as quantitative structure-reactivity/stereoselectivity relationship （QSRR/QSSR）. The multiple correlation coefficient （Rcv= 0.964） was tested through cross-validation with the leave-one-out （LOO） procedure. The above results show that the model possesses high estimation stability and good prediction ability between the amount of both cis and trans isomers in products and reactants.

A Distinctive Pattern for Substituent Effects on Transition Metal Centers:Enhanced Electron-Donating Capacity of Cationic Palladium Species

Electronic and bonding situations at reaction centers are often detected by the remote substituent effect.For nonorganometallic reactions,this effect is conventionally described by the well-known Hammett-type substituent constants.However,for most transition metal(TM)-involved systems,no analogous numeral descriptors reflecting the intrinsic differences between metallic and nonmetallic bonding have been rigorously established till present.Herein,we report a Pd(II)–O bond heterolysis energyΔG_(het)(Pd–O)study of the archetypal palladium complexes to represent the thermodynamics of the essential bond-breaking step in Pd-mediated transformations.Meanwhile we furnish the new substituent constantsσPd^(+)s and therefrom facilitate linear free-energy relationship(LFER)analysis for Pd-catalyzed reactions.Indeed,this led us to find an unexpected electron-donating ability of Pd(II)cation,which provided a gifted experimental support,with the aid of computation,to attribute the frustrating observation of a much scattered curvature in theΔG_(het)(Pd–O)-σ+correlation to the electrondonating capacity of the cationic palladium through back-donation of its d-electrons.Applications of LFER analysis withσPd^(+)to predict the redox behavior of the palladium complex and in a kinetics vs.thermodynamicsmechanistic study of transmetalation added further credence to their applicability to TM systems.