化学英语论文范文和翻译

Computational chemistry that can predict the spectra of a variety of compounds that cannot be obtained aspure compounds was used to study the highly sensitive detection of bromate in ion chromatography. Severalpossible ions, molecules, and their complexes were constructed by a molecular editor, and optimized bymolecular mechanics (MM2) and MOPAC (PM3) calculations. The possible electronic spectra of theseions, molecules, and complexes were then obtained by the ZINDO (INDO)-Vizualyzer in the CAChe program.The lambda maximum (ìmax) of the spectra and the transition dipole were calculated using the ProjectLeaderprogram. The comparison of the experimental and predicted results indicated that Br3- was the probablereaction product, and that NO2- and ClO- accelerated the reaction.1. INTRODUCTIONBromate is considered a carcinogen and the World HealthOrganization (WHO) has recommended the provisionalbromate guideline value of 25 mg/L, which is associated withan excess lifetime cancer risk of 7 10-5, because of thelimitations in the available analytical and treatment methods.1A highly sensitive analytical method was therefore developed.Bromate in ozonized water was detected with veryhigh sensitivity by ion chromatography with a postcolumnreaction detection using ultraviolet absorption. With theaddition of nitrite for the postcolumn reaction, the sensitivitywas improved 738-fold. The detection limit was 0.35 mg/L, and the linear range was >4 orders of magnitude, from0.5 to 10 mg/L.2 The addition of ClO- improved thesensitivity 327-fold.2Chiu and Eubanks3 examined bromide spectrophotometrically;they proposed a reaction mechanism and suggestedthat the end product is tribromide.3 The proposed reactionsare as follows:In addition, bromate and chlorate were determined bypotentiometric titration after reduction with sodium nitrite.4Sodium nitrite was added in sodium bromide for the on-linehydrobromic acid generator in this system, and highlysensitive detection was achieved.2 However, the reactionmechanism and the final product have not been determined.Tuchler et al.5 studied bimolecular interactions and directlydetected the internal conversion involving Br(2P1/2) + I2initiated from a van der Waals dimer. The reaction complexwas formed from a van der Waals dimer precursor, HBrâI2.The resulting product, highly vibrationally excited molecularI2, was monitored by resonance-enhanced multiphotonionization combined with time-of-flight mass spectroscopy.The HBr constituent of the precursor HBrâI2 was photodissociatedat 220 nm. The H atom departed instantaneously,allowing the remaining electronically excited Br(2P1/2) toform a collision complex, (BrI2)*, in a restricted region alongwith the Br + I2 reaction coordinate determined by precursorgeometry. Sims et al.6 reported the fentosecond real-timeprobing of bimolecular reaction Br + I2, and summarized anumber of trihalogen intermediates observed in matrixisolation studies.Computational chemistry can predict the electronic spectraof a variety of compounds that cannot be obtained as purecompounds. This tool was applied to study the highlysensitive detection of bromate in ion chromatography.Several possible ions and molecules and their complexeswere constructed by a molecular editor, and optimized bymolecular mechanics (MM2) and MOPAC (PM3 and AM1)calculations. Their possible electronic spectra were thenobtained with the ZINDO (INDO/1)-Vizualyzer in theCAChe program. The lambda maximum (ìmax) of the spectraof the transition dipole were calculated using the ProjectLeaderprogram. The properties used for the calculation ofthe molecular mechanics were bond stretch, bond angle,dihedral angle, improper torsion, van der Waals, electrostatic(MM2 bond dipole), hydrogen bond, and cut-off distancefor van der Waals interactions (9.00 Å). (van der Waalsinteractions were updated every 50 interactions.) Theparameters for the MOPAC calculation were geometry search* Author to whom correspondence should be sent.† Health Research Foundation.‡ Yokogawa Analytical Systems.Br- + 3ClO- f BrO3- + 3Cl- (1)BrO3- + 5Br- + 6H+ f 3Br2 + 3H2O (2)Br2 + Br- f Br3- (3)J. Chem. Inf. Comput. Sci. 1998, 38, 885-888 885S0095-2338(98)00084-5 CCC: $15.00 © 1998 American Chemical SocietyPublished on Web 08/14/1998options (precise, minimized by NLLSQ, optimized geometryby BFGS), and properties [Mulliken population, energypartitioning, polarizabilities, localize, thermo, rotationalsymmetry (C1)] in the CAChe program. The predicted datawere compared with those obtained experimentally.2. THEORYAccording to the Lambert-Beer law, the ratio of theintensity of the light of the inlet site (Io(î)) and the outletsite (I(î)) is given by the following equation:That is, absorbance A ) log10I/Io ) k(î)Dx, where the molarextinction coefficient (molar absorption coefficient) I ) Io 10k(î)Dx, and k(î): molar extinction coefficient is the molarabsorptivity.The following equation is given as the relation betweenabsorption intensity as measured experimentally and thatestimated theoretically:7The intensity of the spectrum is given by the followingequation:where jájjköâerjiñj2 is the transition dipole.That is, molar absorptivity, k(î), is related to the transitiondipole. The following parameters are found in eqs 4-7: D,concentration of analyte; x, pass length of light; c, light speed;N, Avogadro’s constant; h, Planck’s constant; V, frequency;j, excited state; i, ground state; k, Boltzmann’s constant; er,transition dipole moment; and kö, polarized light vector.3. RESULTS AND DISCUSSIONThe computational chemical calculation was performedby the CAChe program from Sony-Tektronix (Tokyo) usinga Macintosh 8100/100 personal computer. The molarabsorptivity of several ions, molecules, and complexes weredirectly measured on spectra obtained by ZINDO-Visualizationafter their conformations were optimized by MM2 andMOPAC (PM3 and AM1). Their transition dipoles werecalculated by the ProjectLeader program using MM2and MOPAC (PM3 and AM1). The values of molarabsorptivity and the transition dipoles are summarized inTable 1. The values of their complexes with nitrite andchlorite are included. The energy values of angle and vander Waals obtained by the MM2 calculation are also givenin Table 1.The relation between the transition dipole and the molarabsorptivity was:where Y is molar absorptivity (I/mol-cm) and X is thetransition dipole (debye). The chromatographic sensitivityis directly related to the molar absorptivity of the analytes.The molar absorptivity of Br3- and the Br2 + Br- complexwas very high, 190 000. The measurements of molarabsorptivity and the ìmax wavelength were not easilyobtained, but these values can be automatically calculatedusing the ProjectLeader program. The Br3- and the Br2 +Br- complex have similar structures, as shown in Figure 1.The complex between Br2 and Br- was automatically formedafter the optimization of the structure, and the heat offormation energy value was the lowest among the analyteslisted in Table 1; the values were about -106 kcal/mol. Thevalue of the complex was the same as that of Br3-. ThisTable 1. Properties of Analytesaanalyte HOF, kcal/mol ìmax, nm td debye ma, L/mol-cm angle, kcal/mol vwv, kcal/molBr- -56.00 - - * 0.00 0.00Br2 4.92 602 0.277 81 0.00 0.00Br3- -105.69 258 12.300 188200 0.00 0.00BrO3- -39.59 462 0.927 595 3.28 0.00NO2- -42.93 208 4.005 24660 0.00 0.00ClO- -32.97 234 0.409 458 0.00 0.00Br2 + NO2-/1 -98.49 224 7.227 74550 0.00 -0.26Br2 + NO2-/2 -104.80 239 8.183 91440 0.03 -0.05Br2 + NO2-/3 -99.93 230 5.550 43370 0.00 -0.22Br2 + Br- -105.69 258 12.327 188250 0.00 -0.36Br2 + ClO-/1 -113.02 228 4.758 30670 0.00 -0.33Br2 + ClO-/2 -74.52 228 10.385 148400 0.00 -0.46Cl- -51.22 - - * 0.00 0.00Cl2 -11.57 410 0.464 336 0.00 0.00Cl3- -91.06 214 10.615 168200 0.00 0.00Cl2Br- -95.30 247 10.727 148760 0.00 -0.32Cl2 + OCl- -87.51 243 5.220 34 0.00 -0.36BrO3- + NO2- -51.11 209 4.117 30166 0.00 -0.75I3 -85.58 221 12.738 236800 0.00 0.00I2Br -87.59 229 12.276 209360 0.00 0.00a HOF: heat of formation (PM3); td: transition dipole; ma: molar absorptivity; angle: dihedral angle (MM2); vwv: van der Waals energy(MM2); *: molecule lacks electronic state information.Y ) 1057.422X2 + 3017.582X - 2368.256r2 ) 0.993 (n ) 14) (8)[I(î) Io(î)] ) 10-k(î)Dx ) e-ln10âk(î)Dx (4)103âln 10âcNhs k(î)îdî ) 8ð3h2jájjköâerjiñj2 (5)f(theoretical) ) 8ð2mî3hjájjköâerjiñj2 (6)k(î) ) 1Dxlog10 I/Io µ jájjköâerjiñj2 (7)886 J. Chem. Inf. Comput. Sci., Vol. 38, No. 5, 1998 HANAI ET AL.result indicated that Br3- can be formed where Br2 and Brco-exist as the BrI2 complex.5,6The question arises as to how NO2- and ClO- acted inthe reaction: did these ions form different compounds orcomplexes with bromide or bromine for the highly sensitivedetection of bromate? The Br2 + NO2- complex wasthusconstructed, and we optimized the structure by MM2and PM3 calculations. The Br2 and NO2- formed three typesof conformations, as shown in Figure 2. The structures Aand B were obtained as molecules and the structure C wasobtained as a transition state. Their energy values of heatof formation are given in Table 1 as Br2 + NO2-/1, Br2 +NO2-/2, and Br2 + NO2-/3, respectively. Their heat offormation energy values were low; the lowest energy valuewas -105 kcal/mol, about the same as that of the Br2 +Br- complex. The structure with the lowest energy valueis structure B in Figure 2. However, its molar absorptivitywas less than half of that of the Br2 + Br- complex. Thisresult suggested that NO2- may form a complex with Br2;however, such a complex may not be the final productbecause of the low sensitivity. The ìmax wavelengths ofstructures A, B, and C in Figure 2 were 224, 230, and 240nm, respectively, and were different from that of the Br2 +Br- complex and Br3-, whose ìmax was 258 nm. The ìmaxof 258 nm was the closest wavelength to that observedexperimentally (265 nm). This result also suggested thatsuch a complex may not be the final product. The formationof these complexes was supported by the negative values oftheir van der Waals energy calculated by MM2 (Table 1).Bromide did not form a complex with NO2-. Bromide,bromine, bromate, and nitrite were not highly sensitiveanalytes, due to their low transition dipole values and ìmaxwavelength.Another question was why the sensitivity measured in theexistence of ClO- was about the half of that measured inthe existence of NO2-. The reaction processes were estimatedaccording to the proposal of Chiu and Eubanks.3The value of molecular absorptivity of Cl2Br- (148 760) waslower than that of Br3- (188 200), and the ìmax wavelengthof Cl2Br- (247 nm) was also lower than that of Br3- (258nm). Therefore, the final sensitivity using ClO- as thereaction reagent was less than that using NO2-.Bromate formed a complex with nitrite; however, thecomplex may be unstable due to the high energy value ofthe heat of formation. This complex is not a candidate forthe highly sensitive detection of bromate because of the lowtransition dipole value and ìmax wavelength. Bromine canform a complex with ClO-; however, the energy value ofheat of formation was high for a complex with a highertransition dipole. This means that the Br2 + ClO- complexmay be not a candidate for the highly sensitive detection ofbromate. The results just presented indicate that the highlysensitive detection of chlorate and iodinate can be achievedby using the techniques employed for the bromate analysis.The sensitivity of chlorate and iodinate will be 90 and 111%of bromate; however, the ìmax wavelengths of Cl2Br- andI2Br- are 10 and 30 nm lower, respectively, than that ofBr2Br-. IfCl3- and I3- are the final products, the specificion generator should be constructed; however, the detectionwavelengths of Cl3- and I3- are further lower than those ofCl2Br- and I2Br-, and the selective detection may not beeasy. The computational chemical analysis of fluorate couldnot performed due to the lack of stable electron stableinformation for fluorate.An AM1 calculation can be used to optimize thesestructures; however, the present AM1 calculation did not givecomplex forms because of the fixed atomic distances. Theìmax wavelengths were usually shorter than that obtainedby PM3, and the values of molar absorptivity were smaller.For example, the maximum atomic distances of Br3-calculated by PM3 and AM1 were 5.065 and 4.575 Å,respectively. Their ìmax wavelengths and their values ofFigure 1. Electron density of the optimized structures of Br2 +Br- complex and Br3-.Figure 2. Possible conformations of Br2 + NO2-.2BrO3- + 4NO2- + 4H+ f Br2 + 4HNO3 + 2H2O (9)Br2 + Br- f Br3- (10)2BrO3- + 4ClO- + 6H+ fBr2 + Cl2 + 2HClO3 + 3H2O (11)Br2 + Br- f Br3- and Cl2 + Br- f Cl2Br- (12)可以预测有机混合物中一系列有机物色谱的计算化学能在离子色谱中进行溴离子的高灵敏度色谱分析。一些能测的离子，分子和他们的复合物分子结构能通过一个分子编辑器得到。再通过分子力学进一步优化和用MOPAC进一步计算来完善它,这些离子，分子和配和物的电子光谱就会在高度缓存程序中通过ZINDO (INDO)-Vizualyzer方法获得。那色谱和过渡偶极子的最大波长可以通过ProjectLeader程序计算出来。通过实验结果和预测结果的比较表明Br3-是可能的反应产物，而且其中的NO2-和CLO-加快了反应。1. 前言溴酸盐被认为是一种致癌物子和世界卫生组织已建议它的含量准则为25mg/L，这与人一生超过7*10-5 的癌症发病率有关，这是由于以前溴酸盐在有效分析和处理方法上受到限制。因此，一种高灵敏度的分析方法就发展起来了。溴酸盐在溴氧水中通过离子色谱能被精确的检测到，而离子色谱是使用紫外吸收进行柱后反应测定的。随着亚硝酸盐在柱后反应中的加入，灵敏度提高了738倍。检测线0.35mg/L，并且从0.5-10mg/L的线性范围大于四个数量级，CLO-的加入也使灵敏度提高了327倍。Chiu和Eubanks审查了甲基溴光度法，他们提出了一种反应机制，并认为那最终的产物是三溴化物。此外，溴和氯在减少硝酸钠加入量后可通过电位滴定法测得，溴化钠中加入硝酸钠是为了溶液中出现氢溴酸，从而获得精确的测定结果。但是，反应的机制和最终产物仍然是没有确定。图兹勒等人研究双分子的相互作用和发现内部转换Br(2P1/2) + I2开始于范德华二聚体。那反应产物形成范德华二聚体，HBr.I2。那最后产物是高聚物分子，他是通过共振性强的多光子电离法和质谱法相结合而测到的。那HBr.I2的反应产物溴化氢的键长是220nm。氢原子的瞬间离开，使得其余的电子激发Br(2P1/2)，彼此发生复杂的碰撞，形成(BrI2)*。在一个限制的区域伴随着Br- + I2同样取决于反应初始条件。Sims et al，他报告了双分子反应Br- + I2方面的探究结果，总结出了反应中间体在进行分离实验研究时能被观察到。计算化学可以预测混合有机物中一系列有机物的电子色谱，计算化学还应用于精确检测离子色谱中的溴。一些可测的离子，分子和配合物的分子结构通过分子编辑器能被构造出来，再通过分子力学进一步优化和用MOPAC进一步计算。那么他们的电子色谱就会在高度缓存程序中通过ZINDO(INDO)-Vizualyzer方法获得。那色谱和过渡偶极子的最大波长可以通过ProjectLeader程序计算出来。计算化学中的程序还可以计算分子的键长，键角，二面角，扭转力，范德华力，静电力，氢键和由范德华力分离的距离（9.00 Å）。用MOPAC 计算方法计算的参数在下表1，并且各种特性都通过那CAChe程序显现出来了。然后，我们预测的数据就可以和这些实验得出的数据进行比较。文献第三部分：2. 结果与讨论计算化学的计算是由CAChe程序来完成的，这个程序是由东京的索尼泰克公司开发的，更适用于个人电脑。一些离子，分子和配合物的摩尔吸收率能在光谱中直接测量得到，而它们各自的光谱是离子，分子，配合物分子在经过进一步优化和计算后通过ZINDO-Visualization方法而得到的。那ProjectLeader程序用MM2和MOPAC方法可以计算它们的过渡偶极子。摩尔吸收率和过渡偶极子的测试值总结在表1中。它们的复合物如亚硝酸盐和亚氯酸盐的测试值也列在表1中。角度和范德华力的测试值通过MM2计算也被列在表1中。摩尔吸收率和过渡偶极子的关系是：Y = 1057.422X2 + 3017.582X - 2368.256r2=0.993(n=14)(8)其中Y是摩尔吸收率(I/mol-cm)，X是过渡偶极子(debye)。那色谱的灵敏度直接关系到样品的摩尔吸收率。Br3-的摩尔吸收率和Br2 + Br-配合物的摩尔吸收率都很高，大约是190000。摩尔吸收率和最大波长的大小是不容易测得的，但是这些值可以通过ProjectLeader程序自动计算出来。Br3和-Br2 + Br-配合物有类似的结构，如图1所示。在Br3-和Br2 + Br-之间的复合物是在结构的优化中自动形成的，它能量中的热量值是上述表1样品中最低的。那测量值大约是-106kcal/mol.那复合物的测量值是和Br3-的值一样的。这结果表明Br3-能形成诸如BrI2之类的复合物。那么问题就归于了解亚硝酸根和亚氯酸根是怎样参与反应的：这些离子之间可以形成不同的化合物吗？或者由于溴的高灵敏度能与溴化物和溴酸盐形成复合物吗？Br2 + NO2-形成的配合物被构造出来，并且我们通过MM2和PM3计算来优化那结构。那溴与亚硝酸盐就可能有三种不同的构造，这些构造都列在表2中。那A和B是获得的分子，而C是过渡态。它们的热量值分别列在表1中。它们的热量值都很低，其中最低的能量值是-105kcal/mol,这能量值是和Br+Br-的能量值一样的。在表2中可以知道最低能量值的构造是B化合物的结构。然而，它的摩尔吸收率比Br2 + Br-复合物的一半还少。这结果表明亚硝酸根能和溴形成复合物；然而，由于那低的灵敏度得知这种复合物不是最终产物，A,B,C的最大波长列在表2中，一次是224，230和240nm。显然，这是和Br+Br复合物不同的。那最大波长258nm最靠近那理论波长265nm。这结果也表明了那产物不是那最终产物。这些复合物的范德华力通过MM2和PM3计算得知是负值列在表1中。溴化物不能和亚硝酸根形成复合物。溴化物，溴酸盐，溴离子和亚硝酸盐都不是高灵敏度样品，这是由于他们的最长波长和过渡偶极子决定的。

题目：合成和溶液性质高分子两性离子铵betains 摘要：季铵盐， N ， N -二烯丙基氮carboethoxymethyl氮methylammonium氯化物（ 8 ） ，已合成了良好的收益。单体8对聚合反应在水溶液中以过硫酸铵为引发给予聚电解质10 。该聚电解质10对酸性水解了两性聚电解质11日在良好的收益。该解决方案这些性能的聚合物了详细的讨论。该两性聚电解质11显示， “ antipolyelectrolyte ”的行为。 ; 共聚物12季铵盐， N ， N -二烯丙基氮carboethoxymethyl氮methylammonium chlolide （ 8 ）和二氧化硫已合成了良好的收益。该聚电解质12对酸性水解了两性聚电解质13容易在良好的收益。该解决方案性能的这些聚合物中详细讨论。该两性聚电解质13日被裁定为不溶于水，但容易溶解在在场的低分子量的共同盐。该两性聚电解质显示“ antipolyelectrolyte ”的行为;粘度的两性聚电解质增加，增加离子强度，其水溶液的解决办法。