计算多氯代烷烃异构体生成焓的新方法

在我们提出诱导极性叠加原理并用以解释同分异构体稳定性及设计烷烃异构体标准生成焓计算新方法的基础上,进一步设计了含多个杂原子体系的取代烷烃——氯代烷烃异构体生成焓的五参数的新方法.与目前应用较广的九参数的基团加和法相比,计算精度高、预报性好,其预报的均方根误差、平均误差比实验数据的相应偏差还要小.而且,特别重要的是,由于所用的参数少,它在理论上可以推广到含各种杂原子或基团以及多种杂原子或基团共存的化合物生成焓的计算.     

石油中间馏分中异构烷烃的分子识别

以石油加氢异构中间馏分及直馏柴油为研究对象,采用气相色谱/质谱联用技术对异构烷烃的分子形态进行了研究。实验表明各碳数异构烷烃组分在毛细管气相色谱柱上表现出明显的按取代基个数簇分离的现象。对异构烷烃的异构程度进行了表征,得到不同取代基个数的异构烷烃的保留指数(RI)定性表;同时根据化合物的质谱断裂规律,参考文献数据并结合碳数及沸点规律,对73种甲基取代的异构烷烃及10种生物标记的化合物单体进行了结构定性,并计算了保留指数。为在分子水平上认识航空煤油及柴油等石油中间馏分中的异构烷烃提供了基础。定性结果表明:在研究的加氢异构中间馏分中,异构烷烃主要由单取代基和二取代基的异构烷烃组成;而在直馏柴油中,单取代基异构烷烃和类异戊二烯类生物标记化合物丰度较高。     

云南褐煤CO／H2O超临界萃取产物结构分析

对云南先锋褐煤ＣＯ／Ｈ２Ｏ超临界萃取产物进行了元素分析、平均分子量测定和Ｈ－ＮＭＲ、ＦＴＩＲ分析。结果表明，萃取物具有较小的结构单元和较高的杂原子含量，主要由芳环数为２－５，并具有烷基和酚羟基取代度２８－４６％的取代芳香结构组成。对正已烷可溶物柱色谱烷烃馏分和芳烃馏分进行了ＧＣ／ＭＳ分析，在烷烃馏分中检测出一系列烯烃存在，表明在萃取过程中有裂解反就 发生；芳烃馏分以基萘和烷基四氢萘为主要成分，取代     

离子液体/纤维素混配固定相分离性能研究

将丁基修饰的纤维素衍生物C-C4与离子液体键合聚硅氧烷PIL-C12-NTf2混配制成毛细管气相色谱柱C-C4@PIL-C12,用溶剂化参数模型对比研究了此固定相与商品化极性固定相Elite-waxetr和TG-17ms的作用力特征,并考察了此固定相的分离选择性等性能。结果表明,此类纤维素混配柱具有较高的柱效(萘,2778 plates/m,k=6.20,100℃)和较好的耐用性。其特征作用力为氢键碱性、偶极/极化作用以及氢键酸性作用,且强度适中;对芳香异构体、取代烷烃、脂肪酸酯、正构烷烃以及邻苯二甲酸酯的分离选择性优于商品化极性柱Elite-waxetr和TG-17ms。     

双柱气相色谱法测定有机物的正辛醇/水分配系数

通过对烷烃，醇类等有机物在五种不同极性固定相上的气相色谱保留值的测定，提出了从有机物气相色谱保留值测定其正辛醇/分配系数的公式，研究了从不同极性固定相上测得的保留值来测定其分配系数的准确性，得出烷烃类在所有柱上测得的保留值与其分配系数间均具有很好的关联，烷烃醇类在极性相异柱上的保留值之比值与其分配系数间也有很好的相关性，从而为烷烃及醇类等有机物分配系数的测定提供了一种简单、可靠，易行的新方法。     

四氯合锌酸二（正十二烷基铵）晶体相变机理的付里叶变换红外光谱研究

采用变温红外光谱研究了层结构标题配合物的固。固相变机理；相变主要与烷烃链和－ＮＨ＿３极性端基结构变化有关，主要来源于烷烃链的堆积结构和构象的有序。无序变化，同时伴有Ｎ－Ｈ…Ｃｌ氢键强度的降低，由于在高温烃链产生ＧＴＧ＋ＧＴＧ＇和临近端基的ＴＧ构象以及ＧＧ链段，链大量扭曲，形成了烷烃链的“熔化”态，发现同相和异相Ｃ－Ｃ伸缩振动频率对烷烃“链熔化”相变很敏感，可用于表征烷烃链的链长变化。     

直链单烯烃保留指数与分子结构关系的研究

根据同系直链单烯烃保留指数与同碳数正构烷烃保留指数差值与分子碳数间关系曲线拟合,提出预测同系直链单烯烃保留指数的准确公式。在ＳＱ,ＰＦＥ,ＰＥＧ－４０００上,利用所提出的公式对检验集中化合物保留指数预测值与实测值差的标准偏差在±０．９ｉ．ｕ．～±１．５ｉ．ｕ．之间。并且研究发现,同碳数、同几何构型直链单烯烃各位置异构体分子中双键位置与化合物保留指数具有指数关系。首次提出依据分子中双键位置预测其保留指数的准确公式。公式适合各种不同极性固定相。     

毛细管气液色谱保留过程的研究

以ＰＥＧ２０Ｍ为代表研究了石英毛细管柱气液色谱保留过程,提出了利用毛细管柱测定分配和吸附常数的公式,并测定了９个温度下的分配和吸附常数。计算了８０℃和１２０℃下４支不同液膜厚度柱上吸附对保留的贡献。结果表明,在薄液膜的柱子上界面吸附对保留具有重要贡献;温度升高可以降低弱极性化合物（如正构烷烃和饱和醚）吸附对保留的贡献,但对其它化合物影响不明显。验证了正构烷烃、２－酮系列和正构伯醇的吸附常数的碳数规律。     

一种新型的分子内激基缔合物——双-β-萘基烷烃及其衍生物分子内激基缔合物的研究

本文报道几种双-β-萘甲酸多次甲基二醇酯及双-β-萘基烷烃次甲基链上被极性基团取代的衍生物的合成及其荧光谱。结果表明,它们都能形成分子内激基缔合物,对于双-β-萘甲酸多次甲基二醇酯来说,其分子内激基缔合物的荧光强度与链长有关,以三次甲基链为最大。对于双-β-萘基烷烃取代衍生物来说,由于吸电子基团的引入使两个萘环的电子云密度不等,它们所形成的分子内激基缔合物的荧光峰都比未取代的1,3-双-β-萘基丙烷有所蓝移。在极性溶剂乙腈中其分子内激基缔合物的荧光峰的位置虽然不变,但I_E/I₂值则有所降低,表现出既不完全与激基缔合物相同,又不完全与激基复合物相同的性质。     

气相色谱法用于煤油轻镏分烃类组成分析

用氰乙基化反应合成的强极性固定液制成强极性色谱柱!与分子筛柱串联,结合分子筛扣减技术,测定了几种航空煤油油样中正烷烃、芳烃、异构烷加环烷三个烃族组成。进一步用一种弱极性色谱柱与分子筛柱串联,由分子筛扣减法可测定各单体正构烷烃的含量,对所提出的方法的准确度和重复性进行了讨论。@汪燮卿$用氰乙基化反应合成的强极性固定液制成强极性色谱柱!与分子筛柱串联,结合分子筛扣减技术,测定了几种航空煤油油样中正烷烃、芳烃、异构烷加环烷三个烃族组成。进一步用一种弱极性色谱柱与分子筛柱串联,由分子筛扣减法可测定各单体正构烷烃的含量,对所提出的方法的准确度和重复性进行了讨论。     

13C NMR chemical shifts of some highly-branched acyclic compounds

A study has been made of the ¹³C chemical shifts of a number of acyclic alkanes, alkenes, nitriles and ketones which contain quaternary carbon atoms. Similar data have also been obtained for the series of compounds involved in the synthesis of triisopropylacetic acid. Substituent effects and steric factors in these highly substituted compounds are discussed in relation to the chemical shifts.     

Additive components of heteroatom influence in substituted alkanes. Polarization and depolarization of bonds

The general expression for the common one-electron density matrix (DM) of saturated organic molecules obtained previously in the framework of the Hückel type model (V. Gineityte, J. Mol. Struct. (Theochem) 343 (1995) 183) has been applied to reveal the additive components of the heteroatom influence in substituted alkanes. To this end, the occupation number of a basis orbital has been expressed as a sum of three terms describing the polarization and depolarization of bonds and the intramolecular charge transfer. These terms, in turn, have been related to certain types of direct (through-space) and indirect (through-bond) interactions of bond orbitals (BOs). In particular, changes in the secondary polarization of C-C and C-H bonds under the influence of a heteroatom giving rise to their induced dipole moments has been related to differences in the indirect interaction between the two BOs of the given bond before and after substitution. Additive quantum-chemical analogues of the classical inductive and electron-donating effects have been established. The above-mentioned expressions for the occupation numbers have been also applied to substantiate the implicit postulates of the classical chemistry about additivity of the heteroatom influence in substituted alkanes.     

Universal behavior of linear alkanes in a confined medium: toward a calibrationless use of thermoporometry

A general law has been derived for predicting the transition temperature of linear alkanes confined in nanoporous materials from the simple knowledge of the free solvent transition temperature. This law is in very good agreement with the one previously determined for substituted benzenes, attesting a possible universal behavior of confined solvents.     

The enantioselectivity of modified cyclodextrins: Studies on interaction mechanisms

The separation of enantiomers of rather simple molecules, such as alkanes and alkanoic acid esters substituted at the 2-position, has been investigated on alkylated β-cyclodextrin stationary phases. By observing the effect of varying the substrate and the cyclodextrin alkylating agent it has been possible to propose a mechanism for the separation. The most important factors seem to be hydrophobic interactions and the ability of the cyclodextrin to change its conformation to accept the guest molecule.     

Cs2CO3-promoted synthesis of p-terphenyls from allyl ketones

An efficient Cs₂CO₃-promoted synthesis of acylated p-terphenyls from allylic ketones under mild conditions has been developed. The reaction occurred in moderate to good yields and tolerated γ-aryl substituted allylic aryl ketones containing functionalities such as alkanes, ethers and halogens.     

Benchmarking thermochemical experiments and calculations of nitrogen-containing substituted adamantanes

Standard molar enthalpy of formation of 2-cyano-adamantane was obtained by using high-precision combustion calorimetry. The standard molar enthalpies of sublimation of 2-cyano-adamantane and 2,2-dinitro-adamantane at 298.15 K were derived from the vapor pressure temperature dependences measured by transpiration. The molar enthalpies of fusion of these compounds were measured with the help of differential scanning calorimetry. Thermochemical data on functional substituted adamantanes containing nitrogen in the substituents were collected and evaluated. The gas-phase enthalpies of formation were calculated with the high-level quantum-chemical method G4 and compared with the experimental results. The consistent data set of the benchmark quality was suggested for practical thermochemical calculations. Geminal destabilizing effects for the interactions of nitro- and cyano-substituents placed in the second position on the adamantane cage were derived. Structure–property correlations for substituted adamantanes and aliphatic substituted alkanes were found and suggested for the assessment of the gas-phase enthalpies of formation of adamantane derivatives.

     

A non-empirical LCAO MO SCF investigation of electronic relaxation accompanying core ionization in a series of saturated alkanes

Ab initio LCAO MO ΔSCF binding energies and relaxation energies have been computed at the STO-4.31G level for linear and branched alkanes (up to C₆) and are compared with experimental data. The structural dependence of binding energies and relaxation energies is discussed, and it is concluded that binding enegy shifts in these alkanes (compared with methane) arise mainly from relaxation energy changes.     

Novel indium-mediated ternary reactions between indole-3-carboxaldehydes-allyl bromide-enamines: facile synthesis of bisindolyl- and indolyl-heterocyclic alkanes

Indole-3-carboxaldehydes undergo indium-mediated ternary reactions with allyl bromide and indoles to provide symmetrical and unsymmetrical bisindolyl alkanes and with other heterocyclic enamines viz. pyrrole, pyrazole, 6-aminouracil and imidazole to provide indolyl-heterocyclic alkanes in excellent yields. The reactions with substituted allyl bromides proceed with greater ease.     

Molecular mechanics (MM4) study of fluorinated hydrocarbons

A molecular mechanics study of small saturated hydrocarbons (up to C-6) substituted by up to six fluorines has been carried out with the MM4 force field. A parameter set has been developed for use in the calculation of bond lengths, bond angles, torsion angles, conformational energies, barriers to rotation, dipole moments, moments of inertia, and vibrational frequencies for these compounds. The results are mostly in fair to good agreement with experiment and ab initio calculations. The high electronegativity of fluorine leads to serious geometric consequences in these compounds, but these consequences can be dealt with adequately by suitable cross-terms in the force constant matrix, and by recognizing that some of the reference bond lengths and angles (l(0), theta(0)) and the corresponding stretching and bending constant parameters (k(s), k(theta)) that are usually thought of as constants must in fact be treated as functions of the electronegativity of the substituents. Additionally, the heavy mass of the fluorine (relative to the mass of hydrogen in alkanes) leads to large values for other cross-terms that were found to be unimportant in hydrocarbons. Conformational equilibria for polyfluorinated compounds are affected by the delta-two effect well-known in carbohydrates. A few larger fluorinated and polyfluorinated alkanes, including perfluoropropane, perfluorobutane, and Teflon, have also been studied.     

3D Nanoporous FeAl-KIT-5 with a cage type pore structure: a highly efficient and stable catalyst for hydroarylation of styrene and arylacetylenes

A novel bimetallic nanoporous FeAl-KIT-5 catalyst with a cage type porous structure and a high surface area has been prepared for the hydroarylation of styrene and arylacetylenes to afford 1,1-diarylalkanes and 1,1-diarylalkenes, respectively. The catalyst was found to be highly active, and selective, affording a high yield of substituted alkanes and alkenes. The catalyst also showed much higher activity as compared to those of other nanoporous catalysts such as AlSBA-15, AlKIT-5, and FeKIT-5, and can be reused several times without much loss of its activity.