Determination of the n‐octanol/water partition coefficients of weakly ionizable basic compounds by reversed‐phase high‐performance liquid chromatography with neutral model compounds

A strategy to utilize neutral model compounds for lipophilicity measurement of ionizable basic compounds by reversed‐phase high‐performance liquid chromatography is proposed in this paper. The applicability of the novel protocol was justified by theoretical derivation. Meanwhile, the linear relationships between logarithm of apparent n‐octanol/water partition coefficients (logK_ow′′) and logarithm of retention factors corresponding to the 100% aqueous fraction of mobile phase (logk_w) were established for a basic training set, a neutral training set and a mixed training set of these two. As proved in theory, the good linearity and external validation results indicated that the logK_ow′′–logk_w relationships obtained from a neutral model training set were always reliable regardless of mobile phase pH. Afterwards, the above relationships were adopted to determine the logK_ow of harmaline, a weakly dissociable alkaloid. As far as we know, this is the first report on experimental logK_ow data for harmaline (logK_ow = 2.28 ± 0.08). Introducing neutral compounds into a basic model training set or using neutral model compounds alone is recommended to measure the lipophilicity of weakly ionizable basic compounds especially those with high hydrophobicity for the advantages of more suitable model compound choices and convenient mobile phase pH control.     

两种量热模式下物质热分解的动力学补偿效应

热分析量热仪主要包括动态、等温、恒温及绝热四种操作模式。很多学者基于动态及等温模式的测试结果,采用Arrhenius速率常数进行动力学计算,进而发现了所谓的“动力学补偿效应”。为了解绝热模式下是否也存在动力学补偿效应,分别采用绝热加速量热法(ARC)及动态差示扫描量热法(DSC)研究了过氧化二异丙苯(DCP)、40%(质量分数,下同)DCP溶液、葡萄糖、45%葡萄糖溶液的热分解特性,在此基础上基于Arrhenius公式计算了对应的表观活化能E和指前因子A,并对计算结果进行了分析。结果表明:绝热模式下,不同质量的同种样品及其溶液的最佳动力学参数,或者同一组数据采用不同的反应级数获得的lnA和E之间均存在明显的线性关系。此外,尽管由动态DSC数据计算获得的E和lnA普遍小于绝热模式的结果,但两种模式下获得的lnA和E之间仍然存在动力学补偿效应。由此可以推断,具有相同或类似反应机理的反应,虽然实验模式不同,但其E和lnA之间存在明显的动力学补偿效应。     

黄麻基碳纤维/MnO/C锂离子电池负极材料的制备及其电化学性能

利用黄麻碳化后的纤维和吡咯单体作为还原剂,高锰酸钾作为氧化剂,通过原位氧化还原反应法合成了碳纤维/MnO/C一维复合物。扫描电子显微镜(SEM)结果显示,MnO/C纳米颗粒分布在碳纤维的外壁上,MnO被包裹在由聚吡咯碳化而来的碳中,MnO/C纳米颗粒大小为50~150 nm。将制备的产物作为锂离子电池负极材料进行充放电测试,结果表明当电流密度为100mA·g~(-1)时,循环50次后仍具有410 mAh·g~(-1)的比容量,同时也展现了良好的倍率性能。     

高效液相色谱-串联质谱法测定蜂蜜中9种农药残留

建立了同时测定蜂蜜中9种苯并咪唑类和新烟碱类农药的全自动固相萃取-高效液相色谱-串联质谱检测方法。蜂蜜样品用磷酸盐缓冲液（pH=7.8）溶解，超声提取，经亲水亲脂平衡（hydrophilic-lipophilic balance，HLB）固相萃取小柱净化，氮吹浓缩，定容，过滤膜后进行高效液相色谱-串联质谱分析，采用多反应监测（MRM）模式测定，以内标法定量。结果表明，在0.002~0.05 mg/L范围内9种农药呈现出较好的线性关系（相关系数r² ≥ 0.99），检出限和定量限分别为0.1~1.0 μg/kg和0.3~2.0 μg/kg。对阴性蜂蜜，在5.0、10.0、20.0 μg/kg 3个水平下分别进行加标回收试验，测出9种农药的平均回收率在78.2%~101.2%之间，相对标准偏差为1.3%~14.3%（n=6）。该方法可适用于大批量蜂蜜样品的快速准确测定。     

Copper‐Catalyzed Aerobic Oxidative Reaction of Sulfonyl Hydrazides with Alcohols: An Easy Access to Sulfinates

A Cu‐catalyzed aerobic oxidative reaction between sulfonyl hydrazides and alcohols has been developed. In this reaction, sulfonyl hydrazides act as the sulfinic acid precursors to react with alcohols, resulting in sulfinic esters with up to 72 % yield. This catalytic system tolerates a wide range of sulfonyl hydrazide substrates, and represents a new strategy for the transformation of readily available sulfonyl hydrazides.     

Thermodynamic Properties of the Ternary System Potassium Bromide + Lithium Bromide + Water at 25°C

Activity coefficients of potassium bromide in aqueous mixtures of potassium bromide and lithium bromide were determined by emf measurement at 25°C and at six ionic strengths from 0.1 to 2.5 mol·kg^-1. The experimental data were fitted using the Scatchard–Rush–Johnson and Pitzer models. The osmotic coefficients, excess Gibbs energies of mixing, and activity coefficients of lithium bromide in aqueous mixtures were calculated using Pitzer mixing parameters obtained in this work.     

Ti2(OMe)4/SiO2催化剂的制备及其合成碳酸二甲酯的反应性能

采用表面改性和离子交换法制备了SiO2负载的Ti2(OMe)4双核桥联配合物催化剂，用IR、TPD和微反技术考察了催化剂的表面构造及CO2和CH3OH在催化剂表面上的化学吸附和反应性能。结果表明：双核桥联配合物Ti2(OMe)4以Ti-O-Si键锚定在SiO2表面上；CO2在催化剂表面存在桥式和甲氧碳酸酯基两种吸附态，其中甲氧碳酸酯基吸附态是生成DMC的关键物种；CH3OH在催化剂上只有一种分子吸附态。在150℃以下，CO2和CH3OH在Ti2(OMe)4/SiO2催化剂表面上高选择地生成碳酸二甲酯。     

分子印迹手性整体柱的制备及对非对映异构体的分离

 采用原位分子印迹技术 ,单步制备了一种辛可宁印迹的手性整体柱。为了提高柱效和选择性 ,选择了相对低极性的甲苯 /十二醇复合致孔体系。在等度及梯度洗脱条件下 ,非对映异构体辛可宁与辛可尼丁被完全分离。等度洗脱中相对较宽的峰可以在梯度洗脱中得到改善。同时考察了流动相中醋酸浓度、流速以及温度对分离的影响。由于柱中存在大的流通孔 ,大大降低了分离过程中的柱压降 ,从而使这种柱能够在相对高的流速下使用。提高温度可以提高分离因子 ,在 60℃获得最大分离因子 5 40。     

2-呋喃甲硫醇修饰环糊精形成互锁式螺旋柱状超分子的自组装行为

利用单-(6-氧-对甲基苯磺酰基)-β-环糊精和2-呋喃甲硫醇反应得到单修饰环糊精, 单[6-硫-6-(2-甲基呋喃)]-β-环糊精. 通过X-ray衍射分析及核磁光谱等方法研究了其在溶液和固态中形成线状超分子的分子自组装行为. 结果表明, 化合物在固态中通过呋喃基团从第二面羟基连续插入到另一个环糊精的空腔, 形成了互锁式螺旋柱状超分子, 而且在溶液中也显示了相似的自组装行为, 其键合常数K及聚合度n分别为450 mol^-1·L和1.9.