Optimization of parameters for semiempirical methods. III Extension of PM3 to Be,Mg, Zn,Ga, Ge,As, Se,Cd, In,Sn, Sb,Te, Hg,Tl, Pb,and Bi

Using a recently developed procedure for optimizing parameters for semiempirical methods,¹ PM3 has been extended to a total of 28 elements. Average ΔH_f errors for the newly parameterized elements are Be: 8.6, Mg: 8.4, Zn: 5.8, Ga: 14.9, Ge: 11.4, As: 8.5, Se: 11.1, Cd: 2.6, In: 11.3, Sn: 9.0, Sb: 13.7, Te: 11.3, Hg: 6.8, Tl: 6.5, Pb: 7.4, and Bi: 10.9 kcal/mol. For some elements the paucity of data has resulted in a method, which, while highly accurate, is likely to be only poorly predictive.     

Prediction of the enthalpy of vapourisation for anhydrides,formates, acetates,propionates, butyrates,esters, and ethers

Four analytical correlations based on the use of the corresponding states principle were used to calculate the enthalpy of vapourisation of fluids. Three of these correlations require as inputs the critical temperature and the acentric factor. The fourth requires a molecular Lennard–Jones parameter and the acentric factor. Results for 184 polar and non-polar fluids grouped into 9 families are compared with the values accepted by the Design Institute for Physical Property (DIPPR) project. Recommendations are given for the use of each model and for the choice of the adequate model for each family of fluids.     

ICP-AES法测定铝中铁、硅、铜、镓、镁、锌、锰和钛

用 50g L氢氧化钠溶液溶解铝样品 ,硝酸 (1 1 )酸化 ,以ICP AES测定其中铁、硅、铜、镓、镁、锌、锰和钛等 8种杂质元素。     

ICP-MS测定化妆品中铍、镉、铊、铬、砷、碲、钕、铅

目的：建立化妆品中铍、镉、铊、铬、砷、碲、钕、铅8种有害元素的测定方法。方法：采用电感耦合等离子体质谱法,样品采用微波消解,以钇、锂、铟、铋为内标作定量分析。结果：各元素和内标元素在一定浓度范围内的质量数比值均与浓度呈良好的线性关系,线性方程的相关系数均大于0.9998,平均回收率为95%~104%,相对标准偏差(RSD)均小于3%。结论：该方法灵敏度高,准确,可为化妆品中上述元素的限量检查提供参考。     

猪胰脏中铁钙镁铜铅锌镉锰钴镍的测定

采用硝酸－过氧化氢在自动回流消化仪中消化猪胰脏,火焰原子吸收光度法测定铁、钙、镁、铜、锌、铅、镉、锰、钴、镍的含量。,方法简便,快速,结果令人满意,并对猪胰脏食用价值进行了评价。     

Thin-layer chromatographic separation of aldrin,dieldrin, γ-hexachlorocyclohexane,malathion, ethyl-parathion,pentachlorophenol, and of chlordane,dieldrin, γ-hexachlorocyclohexane,malathion, ethyl-parathion,and pentachlorophenol from each other

A thin-layer chromatographic method is reported for the separation of aldrin (or chlordane), dieldrin, γ-hexachlorocyclohexane, malathion, ethyl-parathion, and pentachlorophenol from each other. The procedure, however, does not separate aldrin and chlordane from each other although it does separate either pesticide from the other components. The method employs alumina plates with n-hexane:xylene:benzene:toluene:cyclohexane:methyl cyclohexane (50:50:50:50:50:50:) as developing solvent.     

Enthalpies of dilution of aqueous solutions of formamide,acetamide, propionamide,andN,N-dimethylformamide

The enthalpies of dilution of aqueous solutions of formamide, acetamide, propionamide,N,N-dimethylformamide, and sucrose have been measured from about 0.15 to 2.0 moles-kg ^–1 at 25.0°C. The results of the enthalpy measurements were used to calculate the pairwise enthalpies of interaction for each compound with itself. The equation of Savage and Wood together with their interaction parameters are used to predict the experimental results. All of the predictions are within the standard deviation of the original correlation of Savage and Wood (±220 J-kg-mole ^–2 ). Detailed examination of the results shows that specific effects are present but they are less than 220 J-kg-mole ^–2 . Results on urea and substituted ureas are used to determine interaction coefficients for a urea group with itself and with another CH ₂ group. The result,H _U,U =–280 andH _{U,CH 2} =29 J-kg-mole ^–2 , is an improvement on the previous arbitrary assignment of parameters for urea interactions.     

Theoretical Study of Molecular Structure,Reactivity, Lipophilicity,and Solubility of N-Hydroxyurea,N-Hydroxythiourea,and N-Hydroxysilaurea

Ab initio molecular orbital methods at the CBS-QB3 level of theory have been used to study the structure and gas-phase stability of various tautomers and rotamers of N-hydroxyurea, N-hydroxythiourea, and N-hydroxysilaurea, their anions and protonated forms. The geometries of N-hydroxyurea, N-hydroxythiourea, and N-hydroxysilaurea, their anions and cations were optimized at the Becke3LYP/CBSB7 level of theory. For all compounds studied, the amidic form is computed to be substantially more stable than the iminolic tautomer. N-Hydroxyurea and its thio and sila derivatives are computed to behave as Nacids in the gas phase. These compounds are in gas-phase weak acids with a calculated acidity of about 1425 to 1355 kJ-mol^–1. Basicities increase in the order: N-hydroxyurea < N-hydroxythiourea < N-hydroxysilaurea. The most stable protonated structures are represented by several isomers with almost equal stability. Thus, in the N-hydroxyurea, N-hydroxythiourea, and N-hydroxysilaurea, both protonation at the double bonded (C=O, C=S and Si=O) oxygen and sulfur atoms, as well as the protonation at the N(H)OH nitrogen basic center is equally probable. The experimental pK _a value (10.6) of N-hydroxyurea and the computed value (9.7) for its monohydrated complex with the specifically hydrogen-bonded water molecule to the ionizable OH group are in a good agreement. The experimental partition coefficient of N-hydroxyurea is best reproduced by the Alog P_s method. The formation of nitroxide radical in the reaction of N-hydroxyurea and its sulfur and silicon substituted derivatives with the phenol radical is an exothermic process. Thus, the \bondN(H)OH moiety of these compounds may quench the structurally related tyrosyl radicals in the active site of ribonucleotide reductase.     

Certification of the mass fractions of Ca,Cu, Cl,I, Fe,K, Mg,P, Pb,N, Na and Zn in skim milk powder

Analyses of milk and milk products are routinely performed by a number of dairy laboratories to control the quality of these products with regard to e.g. nutritional components and potential exposure to toxic elements. In order to improve and control the quality of such analyses the Community Bureau of Reference (BCR) has organized series of certification campaigns to produce reference material of milk certified for a variety of elements and compounds. The increasing demand is such that the stock of some of these materials is now exhausted. Consequently, the BCR decided to produce a new batch of CRM of skim milk powder certified for its contents of Ca, Cu, Cl, I, Fe, K, Mg, P, Pb, N, Na and Zn (CRM 063R). This material was carefully prepared (spray-drying) and its homogeneity and long term stability was verified. This paper presents the certification work performed.     

Stereochemistry of the oxidation of 1, 2, 3, 5, 6, 7, 8, 8a-octahydro-1-naphthoic acids

Summary It was shown that the oxidation of syn- and anti-1,2,3,5,6,7,8,8a-octahydro-1-naphthoic acids with peroxyacetic acid and with osmium tetraoxide proceed stereospecifically from the side opposite to that of the carboxy group. On the other hand, the oxidation of syn-cis-1,2,3,5,6,7,8,8a-octahydro-1, 2-naphthalenedicarboxylic acid goes in both of the possible sterically different directions with formation of isomeric- and-epoxides.     

电感耦合等离子体原子发射光谱法测定钨钢中硅、锰、磷、铬、镍、铜、钼、钒和钨

采用电感耦合等离子体原子发射光谱法测定钨钢中硅、锰、磷、铬、镍、铜、钼、钒和钨的含量。试样用盐酸、柠檬酸铵、硝酸溶解。基体效应采用基体匹配法消除。硅、锰、磷、铬、镍、铜、钼、钒、钨的分析谱线依次为288.158,257.610,177.495,267.716,213.604,327.396,204.598,310.230,239.709nm。9种元素的质量分数在一定的范围内与其发射强度呈线性关系,方法的检出限(3s)在0.000 3%~0.004 8%之间。方法用于两种标准物质的测定,测定结果与认定值相符,测定值的相对标准偏差(n=5)在0.74%~2.1%之间。方法的回收率在95.0%~107%之间。     

Determination of traces of As,Cd, Cr,Hg, Mn,Ni, Sb,Se, Sn and Pb in human hair by triple quadrupole ICP-MS

With the wide range of metallic contaminants discharged in the environment, studying the human health requires a growing number of elements to be monitored in biological samples. Hair analysis has been suggested as a suitable tool for biomonitoring environmental and occupational exposure to toxic elements. This study describes a method for the determination of 10 trace elements in hair samples using ICP-QQQ-MS. Combining the power of the MS/MS high-energy Helium mode with the MS/MS O₂ mass-shift mode, the method offers great analytical performances with detection limits reaching 0.0014 µg g^?1 for As, 0.0016 µg g^?1 for Cd, 0.012 µg g^?1 for Cr, 0.0035 µg g^?1 for Hg, 0.0055 µg g^?1 for Mn, 0.10 µg g^?1 for Ni, 0.0012 µg g^?1 for Sb, 0.0083 µg g^?1 for Sn, 0.011 µg g^?1 for Se and Pb. The accuracy of the method was tested on a human hair ERM® certified reference material. Percent recoveries varied from 91.3% and 106.9% being always in the acceptance range of 90–110%. For all analysed elements, RSD% of repeatability ranged between 0.6% and 9.0% and those of intermediate precision did not exceed the limit of 20% being always lower than 10% (except for As). The proposed method was applied for the determination of trace elements in hair samples from 20 unexposed subjects. The geometric mean levels were as follows: Cr 0.28 µg g^?1, Mn 0.30 µg g^?1, Sn 1.04µg g^?1, Sb 0.07 µg g^?1, Hg 0.42 µg g^?1, As 0.02 µg g^?1, Cd 0.03 µg g^?1, Ni 0.51 µg g^?1, Se 0.45 µg g^?1 and Pb 1.83 µg g^?1. Element concentrations were in the same range with the reported data. The reported results may be useful for environmental exposure assessment or comparisons studies when establishing reference values of trace elements in exposed population.     

Certification of the contents of As, B, Cd, Cr, Co, Cu, Mn, Hg, Ni, Ti, V and Zn in a natural Moroccan phosphate rock

Summary The preparation and homogeneity tests of a natural Moroccan phosphate rock are described. The experimental procedures leading to the certification of the contents of As, B, Cd, Cr, Co, Cu, Hg, Mn, Ni, Ti, V and Zn are presented. The Pb-content is given as a recommended value. Indicative values are proposed for Ag, Mo, Sb, Se, Th and U. The certification has been carried out in participation with 11 laboratories from different European countries.

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Zertifizierung der Gehalte an As, B, Cd, Cr, Co, Cu, Mn, Hg, Ni, Ti, V und Zn in einem natürlichen Marokkanischen Phosphatgestein

Zusammenfassung Die Aufbereitung und die Homogenitätskontrollen eines natürlichen Marokkanischen Phosphatgesteins werden beschrieben. Die experimentellen Arbeiten, die zur Zertifizierung der genannten Gehalte geführt haben, werden angegeben. Für Blei wird ein empfohlener Wert gegeben. Indikative Werte werden für Ag, Mo, Sb, Se, Th und U vorgeschlagen. Die Zertifizierung wurde in Zusammenarbeit mit 11 Laboratorien aus verschiedenen europäischen Ländern durchgeführt.

     

Synthesis and characterization of metal-centered, six-membered, mixed-valent, heterometallic wheels of iron, manganese, and indium

Heptanuclear metal-centered, six-membered, mixed-valent, heterometallic wheels 1-3 of iron, manganese, and indium were prepared in a one-pot reaction from N-benzyldiethanolamine (H2L(1)), cesium carbonate, [PPh4]2[MnCl4], and FeCl3 or InCl3. All three complexes were characterized by the combination of elemental analysis, FAB mass spectroscopy, X-ray diffraction and cyclic voltammetry and in the case of 1 additionally by M?ssbauer spectroscopy. In 1, four Mn(II) ions in the periphery are arranged in pairs alternating with one Fe(III) ion each, with an Fe(III) ion located in the center. In 2, three Mn(II) ions alternate with three In(III) ions, whereas in 3, four In(III) ions are arranged in pairs and alternate with one Mn(II) ion each. In 2 and 3 an Mn(II) ion is encapsulated in the center.     

电感耦合等离子体质谱法(ICP-MS)测定稀土矿中钇、镧、铈、镨、钕、钐、铕、钆、铽、镝、钬、铒、铥、镱、镥和钪量

通过用四酸与微波消解法溶解样品对比,建立了用硝酸、盐酸、氢氟酸、高氯酸分解样品,采用电感耦合等离子体质谱法(ICP-MS)测定稀土矿中16种元素含量。方法采用_¹⁰³Rh作为内标消除干扰,确定了最优测定条件,16种稀土元素检出限为0.0029-0.0099ng/mL,测定范围为0.0005-0.020%。精密度试验、加标回收试验及标准物质检测,结果验证了方法的可行性及准确性。该方法简单易操作,结果可靠,能满足实验分析要求。     

RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I

Twenty years ago, the landmark AM1 was introduced, and has since had an increasingly wide following among chemists due to its consistently good results and time-tested reliability--being presently available in countless computational quantum chemistry programs. However, semiempirical molecular orbital models still are of limited accuracy and need to be improved if the full potential of new linear scaling techniques, such as MOZYME and LocalSCF, is to be realized. Accordingly, in this article we present RM1 (Recife Model 1): a reparameterization of AM1. As before, the properties used in the parameterization procedure were: heats of formation, dipole moments, ionization potentials and geometric variables (bond lengths and angles). Considering that the vast majority of molecules of importance to life can be assembled by using only six elements: C, H, N, O, P, and S, and that by adding the halogens we can now build most molecules of importance to pharmaceutical research, our training set consisted of 1736 molecules, representative of organic and biochemistry, containing C, H, N, O, P, S, F, Cl, Br, and I atoms. Unlike AM1, and similar to PM3, all RM1 parameters have been optimized. For enthalpies of formation, dipole moments, ionization potentials, and interatomic distances, the average errors in RM1, for the 1736 molecules, are less than those for AM1, PM3, and PM5. Indeed, the average errors in kcal x mol(-1) of the enthalpies of formation for AM1, PM3, and PM5 are 11.15, 7.98, and 6.03, whereas for RM1 this value is 5.77. The errors, in Debye, of the dipole moments for AM1, PM3, PM5, and RM1 are, respectively, 0.37, 0.38, 0.50, and 0.34. Likewise, the respective errors for the ionization potentials, in eV, are 0.60, 0.55, 0.48, and 0.45, and the respective errors, in angstroms, for the interatomic distances are 0.036, 0.029, 0.037, and 0.027. The RM1 average error in bond angles of 6.82 degrees is only slightly higher than the AM1 figure of 5.88 degrees, and both are much smaller than the PM3 and PM5 figures of 6.98 degrees and 9.83 degrees, respectively. Moreover, a known error in PM3 nitrogen charges is corrected in RM1. Therefore, RM1 represents an improvement over AM1 and its similar successor PM3, and is probably very competitive with PM5, which is a somewhat different model, and not fully disclosed. RM1 possesses the same analytical construct and the same number of parameters for each atom as AM1, and, therefore, can be easily implemented in any software that already has AM1, not requiring any change in any line of code, with the sole exception of the values of the parameters themselves.     

3,3,6,6-四甲基-9-邻氯苯基-1,8-二氧代-3,4,5,6,7,9-六氧化氧杂蒽的合成和晶体结构

标题化合物C23H25对O3Cl是由邻氯苯甲醛与5，5-二甲基1，3-环己二酮在N，N-二甲基甲酸腹中反应而得。结构通过单晶X-射线衍射法确定，其晶体属于单科晶系，空间群=1632。晶体结构用直接法解出，使用全矩阵最小二乘法对原子参数进行修正，最后的偏离因子为R=0．054，Rw一0．063。在晶体结构中，吡喃环与苯环之间的两面角为92．43°。