季铵型阳离子纤维素对水中腐殖酸的吸附

以异丙醇为分散剂,碱纤维与3-氯-2-羟丙基三甲基氯化铵反应,醚化接枝制得一种环境功能材料-季铵型阳离子纤维素（QACC）。用红外光谱、X-射线衍射和电镜扫描对材料的结构进行了表征：红外光谱中1644cm^-1处存在明显的季铵基的弯曲振动。经过改性的QACC结晶度下降,比表面积增加。研究了QACC对腐殖酸的吸附性能：pH=8、318K时,QACC对腐殖酸的饱和吸附容量为622mg·g^-1;其表观活化能为6.45kJ·mol^-1;吸附符合Lagergren二级动力学方程,吸附速率随温度升高而加快;吸附等温模型符合Langmuir等温式,为单分子层吸附;吸附腐殖酸的ΔH、ΔS、ΔG分别为：20.3kJ·mol^-1、77.8J·mol^-1·K-1、-4.44kJ·mol^-1,吸附主要为化学吸附。     

氨基膦酸树脂对溶液中锌的吸附研究

研究了Zn2+在氨基膦酸树脂上的吸附行为。结果表明,静态饱和吸附容量为209.2mg.g-1树脂,用2.0 mol.L-1的HCl溶液洗脱,洗脱率为98%以上;测得吸附热力学参数分别为:ΔH=8.14 kJ.mol-1,ΔG=-3.06 kJ.mol-1,ΔS=37.6 J.mol-1.K-1。等温吸附服从Freundlich吸附等温式;表观活化能Ea=14.7 kJ.mol-1,表观速率常数k298=4.26×10-5s-1;树脂功能基与Zn2+的配位比约为1∶1;并用化学和红外光谱的方法探讨了树脂对Zn2+的吸附机理。     

原位合成羟基磷灰石/壳聚糖复合吸附剂及除氟特性研究

利用原位共沉淀法合成了羟基磷灰石/壳聚糖复合吸附剂,通过扫描电镜、X射线粉末衍射、红外光谱和N2吸附-脱附曲线,研究复合前后羟基磷灰石的理化特征变化。实验结果表明与壳聚糖复合后羟基磷灰石的晶型并没有改变,只是结晶度有所降低,且复合后表面形成了不规则的凹凸结构,表面粗糙度增加。比表面积从106.75m2/g增加到127.58m2/g。复合吸附剂孔径大部分集中在10~50nm,属于介孔结构。利用Langmuir和Freundlich吸附等温方程对实验数据进行了拟合,对比相关系数R2值,Langmuir模型能更好地描述该吸附过程。复合吸附剂对氟离子的吸附符合拟二级反应动力学方程。计算了吸附热力学和动力学参数值,探讨了复合吸附剂对氟离子的吸附机理。ΔG0<0、ΔH0>0和ΔS0>0,说明复合吸附剂对氟离子的吸附是自发的、吸热的熵增过程,温度升高有利于吸附。吸附活化能(Ea)=15.03kJ·mol-1,迁移能(E)=7.639kJ·mol-1,说明该吸附过程以物理吸附为主。     

二甲基胺取代-烃基膦酸树脂对钆(Ⅲ)的吸附性能

用二甲基胺取代 烃基膦酸树脂对钆的吸附行为进行研究,试验结果表明,在pH4.90时,树脂对钆的静态饱和吸附容量为219mg·g-1(树脂);用2mol·L-1HCl可以定量洗脱;表观吸附速率常数k298=1.81×10-4s-1,测得吸附热力学参数分别为:ΔH=77.46kJ·mol-1,ΔG=-32.417kJ·mol-1,ΔS=368.69J·mol-1·K-1;等温吸附服从Frenndlich曲线;树脂功能基与Gd(Ⅲ)的配位比为2∶1;并用红外光谱探讨了树脂与钆的成键情况。     

稻壳灰吸附剂对罗丹明B的吸附性能研究

以发电废弃物稻壳灰为原料,以NaOH为活化剂制备了稻壳灰吸附剂,并将其用于去除水中罗丹明B(Rhodamine B,Rh B)染料。系统考察了溶液pH值、初始浓度、吸附时间、吸附温度以及溶液离子强度对其吸附性能的影响。结果表明:pH=3时,稻壳灰吸附剂对水中Rh B的吸附效果最佳,饱和吸附容量q_m为322. 6mg·g~(-1);吸附热力学研究表明,吸附过程符合Langmuir等温吸附模型。吸附过程焓变ΔH为7. 67 kJ·mol~(-1),ΔS为24. 92 J·mol~(-1)·K~(-1),ΔG0,表明稻壳灰吸附剂对Rh B的吸附过程是自发的吸热熵增过程;吸附过程可在20 min内达到平衡,符合准二级动力学模型;吸附过程的活化能E_a为24. 1 kJ·mol~(-1)。吸附容量随着溶液离子强度的增大而减小,说明其吸附是以静电作用为主的吸附过程。10次循环使用后稻壳灰吸附剂对Rh B的吸附效率仍能保持91%以上,表明该材料可以多次循环使用,是潜在的高效吸附材料。     

中国化学会第21届全国高中学生化学竞赛（决赛）理论试题答案

第1题计算A、B两条直线的斜率:直线A的斜率为-3.76×104直线B的斜率为-1.01×104由Clausius-Clapeyron方程lnp=-ΔvRapTHm C及直线A和直线B的斜率分别得到:ΔHA=84.0kJ.mol-1ΔHB=312.6kJ.mol-1ΔH=ΔHB-ΔHA=312.6kJ.mol-1-84.0kJ.mol-1=229kJ.mol-11-4设xA、xB分别为为DEAA三     

大孔丙烯酸树脂对镧元素的静态与动态吸附研究

研究了大孔丙烯酸树脂(MAR)对镧离子的吸附与解吸行为.静态吸附研究pH值、接触时间和温度对吸附的影响.结果表明,大孔丙烯酸树脂可以有效地将镧离子从水溶液中去除.吸附平衡的时间为14 h.在308 K时,缓冲液pH值6.50,由Langmuir等温线模型得出大孔丙烯酸树脂对镧离子的最大吸附量是379 mg·g-1.吸附过程符合液膜扩散动力学(k=4.37×10-5～5.06×10-5s1).与Freundlich等温线相比,吸附过程更符合Langmuir等温线模型.吸附热力学参数分别为:△H=16.7 kJ·mol-1,△S=130 J·(mol·K)-1,△C298K=-22.0 kJ·ml-1.托马斯模型用于确定动态吸附的特征参数以及预测突破曲线.镧离子可以用浓度为0.5 mol·L-1的HCl溶液洗脱.利用红外光谱技术对大孔丙烯酸树脂的表面进行吸附前与吸附后的表征.     

亚胺基二乙酸树脂对镧(Ⅲ)的吸附及其机制

研究了亚胺基二乙酸树脂(DAAR)对镧离子的吸附行为及机制,pH=5.73的HAc NaAc体系为最佳吸附条件。静态饱和吸附容量为188mg·g-1·R;表观吸附速率常数k298=2.00×10-5s-1,表观吸附活化能Ea=9.57kJ·mol-1;等温吸附服从Freundlich经验式;吸附热力学函数ΔH=10.2kJ·mol-1;ΔS=45.0J·mol-1·K-1;ΔG298=-3.17kJ·mol-1;用0.5mol·L-1HCl作解吸剂,解吸率接近100%;树脂功能基与镧离子的配位摩尔比为3∶1;化学分析及红外光谱表明树脂功能基上的O与La3+发生配位键合。     

高效液相色谱法测定金属配合物｛Fe［3-(2-吡啶基)-5,6-二苯基-1,2,4-三嗪］3｝2+两种几何异构体的动力学转变

通过高效液相色谱法研究了3-(2-吡啶基)-5,6-二苯基-1,2,4-三嗪(PDT)和Fe(Ⅱ)的配合物［Fe(PDT)3］2+的面式和经式两种几何异构体之间的动力学平衡过程。结果表明:不同温度(30,35,40,45 ℃)下,两种几何异构体含量(x)之间的相互转变均符合动力学一级反应,其xeln［(xe-x0)/(xe-x)］值和反应时间t(min)之间的关系分别为:xeln［(xe-x0)/(xe-x)］=0.082t+0.729 (r2=0.9911,T=45 ℃),xeln［(xe-x0)/(xe-x)］=0.049t+0.598 (r2=0.9987,T=40 ℃),xeln［(xe-x0)/(xe-x)］=0.022t+0.586 (r2=0.9987,T=35 ℃),xeln［(xe-x0)/(xe-x)］=0.012t+0.591(r2=0.9988,T=30 ℃)。两种异构体之间的动力学相互转变过程中的活化焓(ΔH)、活化熵(ΔS)和活化能(ΔEa)分别为:ΔH=103.84 kJ·mol-1,ΔS=271.93 J·mol-1·K-1,ΔEa=86.74 kJ·mol-1 (面式异构体向经式异构体转变);ΔH=106.47 kJ·mol-1,ΔS=257.65 J·mol-1·K-1,ΔEa=94.43 kJ·mol-1 (经式异构体向面式异构体转变)。     

外墙保温板残料基活性炭吸附苯酚的研究

活性炭是我们生活中常用的吸附剂,此次研究以外墙保温板残料为碳源制备了活性炭,并考察了所制备的活性炭对苯酚的吸附性能;针对吸附时间、吸附温度、p H、浓度等因素对苯酚吸附的影响,确定了吸附工艺参数:吸附苯酚最优条件为吸附时间90min,温度40℃,p H为4,浓度为0.78mg·m L~(-1),吸附量606.88 mg·g~(-1)。动力学分析:苯酚在外墙保温板残料基活性炭上的吸附符合内分子扩散模型,活化能为Ea=24.5kJ·mol~(-1),苯酚在外墙保温板残料基活性炭上的吸附符合Temkin模型;热力学分析得:在温度低于40℃时,ΔG(0,ΔH=15.761kJ·mol~(-1)(0,ΔS=141.7J·mol~(-1)/K(0,活性炭对苯酚的吸附是自发的吸热过程;混乱度增加,即活性炭更容易吸附苯酚。由此可见以外墙保温板残料为碳源制备的活性炭可以处理应急被苯酚污染的水。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.