NH0-1+2-3离解能等的高级ab initio计算与评价

A recent experimental determination[1] of the dissociation energies (D0) for H2N-H, H2N+-H and H2N-H+, the ionization energies for NH3 and NH2 resulted in large deviations when compared with those of the earlier values and the QCISD(T)/6-311+G(3df,2p) ab initio calculations. We have performed some higher level ab initio calculations on these data by utilizing the Gaussian 92/DFT and Gaussian 94 pakages of programs and have assessed the available experimental values. Our calculations were carried out at the QCISD (TQ)/aug-cc-pVDZ, G2(QCI), QCISD(T)/6-311 ++G(3df,3pd) and QCISD(T)/aug-cc-pVTZ levels of theory. Geometries were optimized at both of the MP2(full)/6-31G(d) and the MP2(full)/6-31(d,p) levels, and were compared with those of the experiments if available. The MP2(full)/6-31G(d,p) tight-optimized geometries for the neutrals are closer to those of the experiments than those of the MP2 (full)/6-31G(d), and are in excellent agreement with the experimental results as shown in Table 1. In this case, we assumed that the optimized geometries for the cations would be better if p polarization functions are added to the hydrogen atoms. We firstly noted that the symmetry of the NH3+ cation was D3h, other than Cs. as reported in ref.[1]. All of the zero-point energies and the final geometries are calculated at the MP2(full)/6-31G(d,p) level of theory. We have also repeated the QCISD(T )/6-311 + G(3df,2p) calculations of ref. [1], because we could not identify their level of goemetry optimization. It is found that the total energy, -55.244 19 Hartrees, for NH2+(1A1 ) in ref.[1] might be in error. Our result is -55.336 29 Hartrees at the same level of theory. At our highest level [QCISD(T)/aug-cc-pVTZ] of calculations as shown in Table 3, the D0 (temperature at zero Kelvin) values of H2N-H, H2N+-H(3B1for NH2+ ) and H2N- H+ are 4.51, 5.49 and 8.00 eV, respectively. These data reported in re f.[1] were 4.97, 5.59 and 8.41 eV, respectively. Our result on D0(H2N-H) supports the work of ref.[2,3,5,6]. The ionization energies (IE) for NH3 and NH2 (3B1 for NH2+) at our highest level are 10.11 and 11.09 eV while in ref.[1] were 10.16 and 10.78 eV, respectively. For the latter, our result supports the experiment of ref.[3]. Our predicted D0 for HN2+-H and IE for NH2 (1A1 for each NH2+) are 6.80 and 12.39 eV, respectively. These values differ greatly from the predicted values (9.29 and 14.88 eV) of ref.[1] where the total energy of NH2+(1A1) might be in error. The D0 value for HN-H has not been found in ref.[1]. Our result supports the work of ref.[3]. We have also derived all of these values at the temperature of 298K and under the pressure of 101kPa at several levels of thoery as shown in Table 3. On examining the experiment of ref.[1] in detail, it is easy to find that all of the larger deviations might be from a too high value of the appearance potential of proton AP(H+). Indeed, ref.[1] has mentioned that the determintion of AP(H+), due to kinetic shift, would lead to a hihger value for the dissociation energy as has been pointed out by Berkowitz and Ruscic. In this work, we concluded that, besides some mistakes in the theoretical calculations of ref.[1], the dissociation energies for H2N-H and H2N-H+,the IE for NH2 (3B1 for NH2+) might also be unreliable and need to be re-examined.
     

取代苯甲醛肟和取代苯乙酮肟电化学氧化机理的研究

研究了１０种取代苯甲醛肟和５种取代苯乙酮肟的电化学氧化机理。这二类肟的氧化电位随取代基吸电子能力的增大而增高，并与它们相应的Ｈａｍｍｅｔｔ常数有线性关系。它们在电化学氧化过程中均有ｉｍｉｎｏｘｙ自由基生成，但最后产物各不相同。用控制电位电解和紫外吸收光谱检法验证了部分电化学氧化产物。因此，电化学氧化法可作为由肟类产生ｉｍｉｎｏｘｙ自由基的一种方法。     

血浆中长链不饱和脂肪酸的毛细管气相色谱分析

脂类物质是细胞膜的主要组成,具有多种重要的生物功能。通过检测血浆中脂肪酸水平,可以研究某些重要疾病与脂质及脂肪酸的关系。特别是长链不饱和脂肪酸,由于它们是前列腺素的前体,更具有重要意义,血浆中长链不饱和脂肪酸,其中8,11,14—廾碳三烯酸(C_(20:)     

加速溶剂萃取/液相色谱-串联质谱测定底泥中氯硝柳胺及其降解产物

建立了加速溶剂萃取/液相色谱-串联质谱分析底泥中氯硝柳胺及其降解产物(5-氯水杨酸和2-氯-4-硝基苯胺)的方法。以中性氧化铝作为池内吸附材料,集提取和净化于一步,乙腈-水(3∶1,体积比)作为萃取溶剂,优化了温度和静态萃取时间等参数。在优化条件下,氯硝及其降解产物在0.1~20.0μg/L范围内有良好线性关系,相关系数(r)均大于0.999。方法的检出限和定量下限分别为0.04~0.1μg/kg和0.2~0.5μg/kg。用于底泥中氯硝柳胺及其降解产物的分析,在0.5、1.0、2.0μg/kg加标水平下,平均加标回收率为93.5%~101.9%,相对标准偏差为3.7%~6.7%。该方法简便,灵敏度高,重现性好,可应用于实际样品分析。     

电感耦合等离子体发射光谱法测定土壤中10种重金属

建立电感耦合等离子体发射光谱法测定土壤中Ba,Cd,Co,Cr,Cu,Mn,Ni,Sr,Pb和Zn 10种重金属的含量。以国家标准土壤样品GSS–1,GSS–2,GSS–3为研究对象,采用硝酸、盐酸、氢氟酸和高氯酸微波消解,赶酸后加入2 m L 2%的柠檬酸溶液作为络合剂,在选定的仪器工作条件下测定,10种元素的质量浓度在0~20μg/m L范围内与光谱强度存在良好的线性关系,相关系数均大于0.999,方法检出限为0.01~0.15μg/m L。测定结果的相对标准偏差为0.86%~4.82%(n=6),10种重金属平均加标回收率为95.17%~108.67%。该方法操作简单、稳定性好,适用于土壤中重金属含量的测定,并为络合剂在元素测定中的应用提供参考。     

室温自交联型聚丙烯酸酯纳米乳液的研究

本文分别用反应性乳化剂和常规乳化剂合成了室温自交联丙烯酸纳米乳液,并对其乳液的流变性能进行了研究,发现:反应性乳化剂所得乳液的表观粘度ηa、稠度系数K、零剪切粘度η0均比常规乳化剂所得乳液的增大。并用XPS对乳胶膜进行分析表明,反应性乳化剂在乳液的干燥成膜过程中不易向胶层表面迁移富集。与常规乳化剂体系的乳液相比,反应性乳化剂体系的乳液挥发速率快,吸水率低。并对两种乳液进行了粒径大小及分布的表征。     

高分子多孔微球富集－HPLC法测定水体中的有机磷

本文提出应用国产高分子多孔微球－ＧＤＸ系列富集－反相高效液相色谱法测定废水中久效磷、乐果、甲基对硫磷三种有机磷农药分析方法。三种不同型号色谱固定相（ＧＤＸ－１０２，ＧＤＸ－３０１和ＧＤＸ－５０１）对水体中ｎｇ／ｍＬ级久效磷、乐果和甲基对硫磷的富集效率分别达到８５％、８２％和９３％以上。采用μ－ＢｏｎｄａｐａｋＣ１８作固定相，以６０％甲醇水溶液作流动相，对三种有机磷农药的分离度可达到１．２以上。本法用于分析水体中有机磷农药，结果令人满意。     

C-410树脂分离富集-电感耦合等离子体质谱法测定地质样品中的金、铂、钯

研究了地质样品中超痕量Au,Pt和Pd的测定方法。采用C－410阴离子交换树脂在1．5mol/L HCl条件下对Au,Pt,Pd的吸附率分别为91．2％、100．0％、95．7％。共存离子除Ge^4 ,Cr^6 ,Ti^4 外，无显著性干扰，用ICP－MS测定Au,Pt,Pd的检出限分别为0．27、0．40和0．19μg/L。当n=8时，Au的RSD为19．2％；Pt的RSD为28．1％；Pd的RSD为15．6％。     

几种C_(60)环加成物的结构及光谱的理论研究

用INDO系列方法研究了C60的几种环加成衍生物C68H8、C68H6O、C68H4O2的结构和UV谱．结果表明，C68H8的［6，6］异构体的船式构象比平面构象稍稳定，两者能量差为9．6kJ／mol；而随着衍生物中羰基的增加，C60母体也由电子受体变为电子给体．以优化构型为基础，计算产物的UV谱，对电子跃迁进行理论指认，并分析了光谱红移的原因．     

N—异丙基甲基丙烯酰胺共聚热缩温敏水凝胶

从甲基丙烯腈与异丙醇反应制备了Ｎ－异丙基甲基丙烯酰胺（ＮＩＰＭ），研究了其以Ｎ，Ｎ＇－亚甲基双丙烯酰胺（ＭＢＡ）为交联剂在不同溶剂体系的聚合及所形成的水凝胶的性质。表明ＮＩＰＭ－ＭＢＡ凝胶具有热缩温敏性。在ＮＩＰＭ－ＭＢＡ体系引入丙烯酸钠、甲基丙烯酸钠等负离子单体时，凝胶的溶胀比明显增加，ＭＢＡ所占比例较少的体系，具有热缩、热胀双重性。