单取代烷烃的熵和吉布斯自由能与分子结构的关系

将单取代烷烃RX(X=OH、SH、NH2、Cl、Br、I、NO2、CN等)分子结构分为两个区域R和X来提取分子结构参数,从三方面影响因素:烷基R、取代基X、R与X相互作用来定量关联RX标准摩尔熵及标准摩尔生成吉布斯自由能。获得了已有实验测定的单取代烷烃RX标准摩尔熵及标准摩尔生成吉布斯自由能,并以烷基的碳原子数、取代基X对所研究单取代烷烃热力学性质的贡献值,烷基的极化效应指数与取代基电负性的乘积三参数为变量,建立定量相关模型,采用留一法交叉验证这些方程,结果表明,模型方程都具有良好的稳定性和预测能力。     

Development of a nonaqueous solvent system for poly(vinyl alcohol) and its characterization

Solubility of poly(vinyl alcohol) (PVA) in water prevents the preparation of various derivatives through homogeneous techniques as most of the derivatives thus formed are insoluble in aqueous medium. There are a number of solvents that can swell PVA under hot conditions but cannot dissolve PVA. In the present study, N,N‐dimethyl acetamide (DMAc) has been identified as solvent in which PVA can be dissolved in the presence of an equimolar amount of lithium chloride (LiCl). ¹H nuclear magnetic resonance (¹H‐NMR), ¹³C‐NMR, infrared (IR), and X‐ray diffraction (XRD) studies have been carried out to characterize the regenerated poly(vinyl alcohol) (RPVA). DMAc–LiCl is found to be a true solvent system for dissolution of PVA. An attempt has also been made to prepare poly(vinyl acetate) from this solution of PVA by a homogeneous technique. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 663–669, 1999