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1.
六次甲基四胺(HMT)与氯化苄加成所得的Sommelet反应中间产物的单晶样品用SYNTEX R3型四圆衍射仪,以θ/2θ扫描方式收集了2677个衍射数据并进行了结构分析.晶体属空间群P2 12 12 1.晶胞参数α=7.692(1)Å,b=18.405(3)Å,c=19.059(3)Å,晶胞中含八个G 6H 5CH 2Cl·N 4(CH 2) 6.经PL,K,B及吸收因子的校正得绝对强度.全部非氢原子坐标的初始参数由SHELXTL直接法程序所得的E图导出.对坐标及热参数经六轮块矩阵最小二乘法修正,再加入氢原子修正两轮后得一致性因子R 1=0.040,R 2=0.032(加权).结构分析证实,此Sommelet反应中间物由季胺盐阳离子与氯离子所组成.在晶体中观察到苄基与HMT中N *直接键连,并导致HMT中N *—C *键有极显著的键长增长效应,而与N *—C *邻接的C *—N键则有所增强.由此预期当此加合物水解时,N *—C *弱键首先瓦解是较合理的. 相似文献
2.
迄今为止,Gran法以直线外推法计算结果,而此法涉及的直线的斜率和截距两个参数的误差基本上是迭加的,因此误差较大。本文导出了简单、准确的斜率法计算公式,并在此基础上提出了一个由斜率法和外推法组合的Gran法计算图。 1.方法的理论基础和计算公式的导出: (1)理论基础:设被测试液的浓度为C_0,体积为V_0,电动势为E_0;于试液中连续I次加入浓度为C_s的标液体积分别为V_s 毫升,加入的总体积为VsI毫升,得到相应的电动势为E_I 毫伏。如令△E_I=E_I-E_0;x=C_sV_g/C_0V_0;a=V_g/V_0;y_r=(1+al)10~(△E)_I~(/S),则有 相似文献
3.
本工作采用密度泛函理论(DFT)方法计算研究了不同电场强度下偶氮苯衍生物2'-对甲苯偶氮基-1,1':4,4'-三苯基- 4,4'二羧酸(TTDA)顺反异构化反应的机理. TTDA经过C—N 1=N 2角度顺反异构化过程存在三种可能的异构化模式 (N=N偶氮基团中与大取代基相连的N原子称为N 2, 与小取代基相连的N原子称为N 1), 绕N 1或N 2原子的反转和绕N 1=N 2键旋转. 计算结果表明, 加入沿 z轴的电场(以三联苯侧链C 1→C 2方向为 z轴正方向), 旋转路径为反应最优路径. 此外, 还研究了沿N=N键方向加入电场(以N 2→N 1方向为 z轴正方向), 在电场强度 Fz=0.00 V•Å -1时, N1反转路径能垒较N2反转路径高. 当–0.62 V•Å -1< Fz≤0.93 V•Å -1时, 旋转路径为优势路径. 当加入沿 z轴的反向电场–0.93 V•Å -1≤ Fz≤–0.62 V•Å -1时, N2反转为优势路径. 相似文献
4.
采用TPD实验方法测定了N 18O在SrTiO 3表面吸附后的脱附谱, 揭示了气体脱附量的变化规律. 结果表明N 18O在SrTiO 3表面吸附后脱附出大量的N 16O气体, 还脱附出少量的N 2, N 18O和N 216O气体. 这说明了在吸附和脱附过程中N 18O与SrTiO 3表面发生氧的同位素交换. N 16O的脱附量随N 18O气体暴露量增加而增加, 但当气体覆盖度超过一定值后, 脱附量趋于定值. 相似文献
5.
提出了固相萃取-液相色谱-串联质谱法测定尿液中四氢大麻酚(THC)和Δ 9-四氢大麻酸(THC-COOH)含量的方法。取尿液样品1 mL,加入1 mol·L -1 NaOH溶液1 mL,于60℃加热15 min后过活化好的MAX混合阴离子固相萃取柱。用1 mL 2%(体积分数)氨水溶液固定目标物,用1 mL 80%(体积分数)甲醇溶液进行淋洗,最后用1 mL含5%(体积分数)甲酸的甲醇溶液进行洗脱,收集洗脱液,按照仪器工作条件进行测定。以Agilent Poroshell HPH-C 18色谱柱(50 mm×4.6 mm, 4μm)为固定相,以不同体积比的5 mmol·L -1乙酸铵溶液-甲醇混合液为流动相进行梯度洗脱;分离后的THC和THC-COOH经电喷雾离子源负离子模式扫描,多反应监测模式检测。结果表明:THC和THC-COOH的质量浓度在一定范围内与对应的峰面积呈线性关系,检出限(3S/N)分别为0.003,0.05μg·L -1;按照标准加入法对空白样品进行加标回收试验,回收率... 相似文献
6.
离子选择电极分析中,为了消除液接电位导致的误差,可利用另一离子电极作为参比电极,只要在试液中保持该离子的活度恒定即可。采用同价态离子电极互作参比电极时,能以标准比较法测定试液中相应离子的活度或浓度比,还可用标准加入法或Gran作图法分别测定相应离子的浓度。标准加入法不必考虑加入的标准液的稀释影响,直接用下式计算。 相似文献
7.
测定了278.15~318.15 K(间隔10 K)下葡萄糖+HCl+水三元体系的密度, 计算了葡萄糖在盐酸(浓度0.2~2.1 mol•kg –1)中的表观摩尔体积 VΦ,G、标准偏摩尔体积 V0Φ,G、葡萄糖-HCl在水中的体积对相互作用参数 VEG和标准偏摩尔膨胀系数(∂ V0Φ,G/∂ T) p. 结果表明: (1)葡萄糖在盐酸中的表观摩尔体积随葡萄糖和HCl的浓度的增加而线性增大; (2) V0Φ,G随HCl的质量摩尔浓度的增加而线性增大; (3)葡萄糖与HCl在水溶液中的体积相互作用参数 VEG>0, 但数值对温度变化不甚敏感; (4)葡萄糖在水和盐酸中的 V0Φ,G值随实验温度的变化关系均可表示为: V0Φ,G= a0+ a1( T-273.15 K) 2/3; (5) (∂ V0Φ,G/∂ T) p为正值且随温度的升高而减小; 在一定温度下, 其值随HCl浓度的增加而稍稍减小. 糖的水化程度随温度的升高和HCl的浓度的增加而减小. 用结构相互作用模型对葡萄糖与HCl之间的体积相互作用进行了解释. 相似文献
8.
在所有DNA碱基中, 鸟嘌呤碱基G具有最低的氧化电位, 导致其最容易被氧化. G碱基被单电子氧化成为G正离子自由基(G +·), G +·存在两个脱质子位点, 其中脱嘧啶环上亚氨基质子N 1-H比脱环外氨基质子N 2-H更有利, 因而在普通G碱基中研究脱N 2-H的过程无法排除脱N 1-H过程的干扰, 使得其脱N 2-H的动力学迄今尚不明确. 在本文中, 通过将G碱基上的N 1-H用CH 3取代(即mG), 采用纳秒时间分辨瞬态紫外可见吸收光谱方法研究了mG碱基单电子氧化后脱质子N 2-H的动力学. 根据瞬态紫外可见吸收光谱, 确定了mG +·脱质子的产物是mG(N 2-H) ·, 即脱质子的位点是N 2-H. 进一步通过测量mG(N 2-H) ·的生成速率常数与mG的浓度依赖关系, 得到室温下SO 4-·单电子氧化mG生成 mG +·的速率常数为(3.7±0.1)×10 9 L·mol -1·s -1以及 mG +·脱N 2-H的速率常数为(7.1±0.2)×10 6 s -1. 并通过检测不同温度下mG +·脱N 2-H的速率常数, 利用阿仑尼乌斯方程得出脱质子N 2-H的活化能为19.9±1.0 kJ·mol -1. 这些结果可为DNA碱基的氧化损伤过程提供更为丰富的动力学信息. 相似文献
9.
邻苯二酚紫在NH 4Ac(pH4.7)底液中还原,产生良好的示波极谱图,E p1=-0.66V(vs.SCE).加入A1 3+后,此波高降低,并在稍负的电位上出现一个尖峰形的新波(E P2=-0.85V),其峰电流与铝的浓度在1×10 -6-1.2×10 -5M范围成正比,此波可用于测定铝,实验表明,该波属于络合吸附波,用连续变化法确定络合物的络合比为1:1。 相似文献
10.
在5 g婴幼儿辅食果泥样品中加入乙酸乙酯20 mL和氯化钠3.0 g,涡旋2 min,离心5 min,用20 mL乙酸乙酯重复提取一次,合并两次上清液,于40℃减压浓缩至近干,加入5 mL甲醇溶解残渣。所得溶液过活化好的C 18固相萃取柱,收集全部流出液,于40℃氮吹至近干,加入1 mL正庚烷,涡旋1 min溶解残渣,过0.22μm有机相滤膜,滤液用超高效合相色谱法(UPC 2)分析。以Acquity Trefoil AMY1色谱柱为固定相,以不同体积比的含0.5%(体积分数)氨水的甲醇溶液和超临界二氧化碳的混合溶液为流动相进行梯度洗脱,在230 nm波长下检测(-)-甲氰菊酯和(+)-甲氰菊酯,外标法定量。结果显示,甲氰菊酯对映体的质量浓度在1.0~20.0 mg·L -1内和对应的峰面积呈线性关系,测定下限(10S/N)均为0.2 mg·kg -1。对阴性果泥样品进行3个浓度水平的加标回收试验,两种目标物的回收率为81.4%~106%,测定值的相对标准偏差(n=6)为4.1%~7.2%。方法用于20份果... 相似文献
11.
格兰图在离子选择电极法中应用广泛,但该图要求电极响应的能斯特斜率为一定值。对电极斜率偏离理论值的情况进行修正已有报道。 本文提出一种不需任何电极斜率校正步骤的算图,即以加入标准溶液后电位的变化值△E与实际斜率S的比值△pe对加入标准溶液体积Vs作图的计算图(简称为△pe格兰图)。在实际操作中,根据测得的△E值和S值,经换算为△pe后,即可在标准算图上作图进行结果计算。克服了作空白溶液线或共线图线时可能引进的误差,简化了结果处理过程。此外,对不同价态离子的测定,该算图纵坐标标度△pe不变,不必扩大或缩小,作图十分方便。 相似文献
12.
用INDO系列方法对由(C 59N) 2和苯甲醚合成的衍生物C 59(C 6H 4OCH 3)N进行了理论研究,得到了分子的稳定构型.结果表明,C 59(C 6H 4OCH 3)N具有C s对称性.以优化构型为基础讨论了分子的UV-Vis光谱、NMR谱线数,结果与实验符合得很好.本文还计算了C 59(C 6H 4OCH 3)N的二阶非线性光学系数β μ,结果表明这种物质具有较大的二阶非线性光学系数. 相似文献
13.
An ion retarding potential difference (IRPD) method has been used to investigate the ion yield and kinetic energy distributions of N +/N 2 produced by photoionization mass specrometry using synchrotron radiation. Photoion yield curves of energy selected N + ions are deduced. Translational energy distribution of N + at energies of the N(1s)→π*, N(1s)→( nl) 1 and above the N(1s) −1 threshold are determined. Comparison is made with previous photoin-photoelectron coincidence work using time-of-flight (TOF) measurements. 相似文献
14.
As a class of metal-free two-dimensional (2D) semiconductor materials, polymeric carbon nitrides have attracted wide attention recently due to its facile regulation of the molecular and electronic structures, availability in abundance and high stability. According to the different ratios of C and N atoms in the framework, a series of C xN y materials have been successfully synthesized by virtue of various precursors, which further triggers extensive investigations of broad applications ranging from sustainable photocatalytic reactions and highly sensitive optoelectronic biosensing. In view of topological structures on their electronic structures and material properties, the as-reported C xN y could be generally classified into two main categories with three- or six-bond-extending frameworks. Owing to the effective n→ π* transition in most C xN y materials, the relative energy level of the lone-pair electrons on N atoms is high, which thus endows the materials with the capability of visible light absorption. Meanwhile, the different repeating units, bridging groups and defect sites of these two kinds of C xN y allow them to effectively drive a diverse of promising applications that require specific electronic, interfacial and geometric properties. This review paper aims to summarize the recent progress in topological structure design and the relevant electronic band structures and striking properties of C xN y materials. In the final part, we also discuss the existing challenges of C xN y and outlook the prospect possibilities. 相似文献
15.
用INDO系列方法对C 60O 3的可能构型进行研究,结果表明:环氧结构邻近的6-6键易发生进一步的加成反应.其中3个氧原子加在同一个六元环的6-6边上,形成环氧结构最稳定的C 3v构型,第3个氧原子加在2个环氧结构相邻的六元环的6-6边上的C 2、C s构型也相当稳定,C 2、C s构型的部分 13C NMR谱与实验吻合.C 60O 3可能有较好的反应活性,其电子光谱属于理论预测. 相似文献
16.
A procedure is described for the estimation of metallic iron, ferrous oxide, and ferric oxide when present together. The sample is treated with bromine dissolved in ethanol, and filtered. Iron in the filtrate is titrated iodometrically, and corresponds to the metallic iron present in the mixture. The oxide residue is dissolved in hydrochloric acid under a carbon dioxide atmosphere. The iron(II) formed, equivalent to FeO present, is titrated with a standard vanadate solution, and the total iron(III) (FeO + Fe 2O 3) in the titrated solution is then estimated iodometrically. 相似文献
17.
本文基于自由能函数随温度变化极为缓慢的特性,按热力学基本关系式简捷地导得了一个不需热容数据的平衡常数近似式(简称无热容近似式),应用该式仅需一个温度下的K_p值和可自手册查得的标准生成热及标准熵的数据即可在较宽的温度范围内求得另一温度下的K_p值,且具有较高的准确度。 相似文献
18.
The crystal and molecular structures of two quarternary salts of 2-oxosparteine (II), the methiodide (IICH +3 • I −) and the methperchlorate (IICH +3 • ClO −4) have been determined on the basis of X-ray and IR data. The studies were performed by analogy to previously investigated quaternary salts of sparteine (I), the methiodide (ICH +3 • I −) and the methperchlorate (ICH +3 • ClO −4). As expected, the configurations and conformations of cationic parts within the two pairs of quaternary salts are identical, except for the structure of their A/B fragments, which in ICH +3 cations have the character of tertiary amines, but in IICH +3 that of lactams. On the basis of accumulated X-ray and IR data the similarities and differences in the modes of interaction of perchlorate and iodide anions with quaternary cations, and especially with their N+---CH3 groups are discussed. In this discussion are also included the methiodide and methperchlorate of -isosparteine: IIICH+3 • X− (X− = I− or ClO−4) where N+---CH3 groups are cisoidally oriented to the basic nitrogen atoms. The most interesting observations are as follows: (i) When N+---CH3 groups are easily accessible for direct quasi hydrogen bonding interactions with counter anions and when other positive charged groups, for instance lactam groups, are absent in quaternary cations, perchlorate anions interact more strongly than the iodide anions and in consequence introduce conformational changes into the ring with N+---CH3 group as well as into further rings. (ii) Perchlorate and iodide anions interact with N+---CH3 groups similarly and very weakly if at all, when the N+---CH3 groups are for steric reasons inaccessible to counter anions or when in quaternary cations there are additional groups which attract the counter anions electrostatically. The last mechanism operates in both quaternary salts of 2-oxosparteine and this is the reason why their monocrystals are isosteric and IR spectra almost identical. (iii) The sterically hindered N+---CD3 groups in both IIICD+3 • X− salts give rise in their IR spectra to two doubles of sharp, well resolved bands which indicate the presence of two different rotamers stabilized by two modes of weak intramolecular hydrogen bonds with basic N atoms. (iv) In IIICH+3 • X− and IIICD+3 • X− salts the perchlorate and iodide anions do not interact at all with the rotating and vibrating N+---CH3 (N+---CD3) group but the structures of these salts are not isosteric since the perchlorate anions interact more strongly than iodide anions with the A/B fragment of the IIICH+3 cations. This is visible from the shapes and intensities of the so-called “trans” band in the IR spectra of both salts. 相似文献
19.
用B 3LYP/6-311G(d,p)密度泛函方法对B 2H 5+阳离子和B 2H 5·自由基的几何异构体的空间构型进行了优化,并在此基础上用QCISD(T)/6-311++G(3df,2p)偶合簇法进行了单点能计算和零点能校正.结果表明,B 2H 5+单态有2种稳定的几何构型(D 3h,C 1),其中C 1构型是新发现的.B 2H 5+三重态阳离子除已知C s构型外,又发现两种稳定构型(C 1).对于B 2H 5·自由基体系,共有4种异构体(包括两种新发现的构型C s),其中,具有单桥结构的C 2v最稳定.用二级多体微扰理论和密度泛函方法对前人所认为稳定的B 2H 5+单态的C 2v构型进行了全优化,结果发现该构型始终具有一个虚频,不是稳定构型.对B 2H 5-阴离子体系的单态和三重态进行的全优化,理论上得出单态时具有C 2v和C s两种稳定构型,而三重态只有C 2v一种稳定构型. 相似文献
20.
We have investigated the lowest-energy structures and electronic properties of the 20-atoms coinage metal clusters (Cu 20, Ag 20, and Au 20) using density functional theory (DFT) within generalized gradient approximation. The most stable configurations obtained for Ag 20 and Au 20 clusters are tetrahedral structures T d symmetry), while compact structure with C s symmetry is preferred for Cu 20. Large HOMO–LUMO gap is found for Au 20 and Ag 20 with tetrahedral structures, while it is much small in the Cu 20 isomer with tetrahedral structures. The compact C s structure of Cu 20 has large gap comparable to that of Au 20 with tetrahedral structure. 相似文献
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