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991.
Zou JW Jiang YJ Guo M Hu GX Zhang B Liu HC Yu QS 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(2):740-751
Ab initio calculations have been performed on a series of complexes formed between halogen-containing molecules and ammonia to gain a deeper insight into the nature of halogen bonding. It appears that the dihalogen molecules form the strongest halogen-bonded complexes with ammonia, followed by HOX; the charge-transfer-type contribution has been demonstrated to dominate the halogen bonding in these complexes. For the complexes involving carbon-bound halogen molecules, our calculations clearly indicate that electrostatic interactions are mainly responsible for their binding energies. Whereas the halogen-bond strength is significantly enhanced by progressive fluorine substitution, the substitution of a hydrogen atom by a methyl group in the CH(3)X...NH(3) complex weakened the halogen bonding. Moreover, remote substituent effects have also been noted in the complexes of halobenzenes with different para substituents. The influence of the hybridization state of the carbon atom bonded to the halogen atom has also been examined and the results reveal that halogen-bond strengths decrease in the order HC triple bond CX > H(2)C=CHX approximately O=CHX approximately C(6)H(5)X > CH(3)X. In addition, several excellent linear correlations have been established between the interaction energies and both the amount of charge transfer and the electrostatic potentials corresponding to an electron density of 0.002 au along the R-X axis; these correlations provide good models with which to evaluate the electron-accepting abilities of the covalently bonded halogen atoms. Finally, some positively charged halogen-bonded systems have been investigated and the effect of the charge has been discussed. 相似文献
992.
V. P. Borovik I. Yu. Bagryanskaya Yu. V. Gatilov O. P. Shkurko 《Journal of Structural Chemistry》2003,44(4):650-654
The crystal structures of 2-amino-4-phenyl-9H-pyrimido[4,5-b]indole and its nitrate were determined by XRD analysis. 13C NMR, XRD, and quantum-chemical data indicate that the acid proton is predominantly localized at the N(3) atom of the pyrimidine ring in both isolated nitrate molecules and in molecules in crystal and solution. 相似文献
993.
V. K. Turchaninov N. N. Chipanina T. N. Aksamentova M. S. Sorokin V. A. Pestunovich 《Russian Chemical Bulletin》1998,47(2):231-236
Five ionization potentials for thesp,ac andsp, sp conformers of (acetylthiomethyl)trifluorosilane MeC(O)SCH2SiE3 and six ionization potentials for the same conformers of (benzoylthiomethyl)trifluorosilane PhC(O)CH2SiF3 were calculated by the semiempirical AM1 method. The resulting values are in good agreement with the data of photoelectron
spectroscopy only for thesp.ac conformers. The structure of the preferred conformer of (acetylthiomethyl)trifluorosilane was confirmed by measurement of
its dipole moment in the gas phase. The influence of the long-range inductive effect (field effect) on the energy of nonbonding
electrons of the carbonyl oxygen atom in the series of acetic acid derivatives was observed.
For Part 9, see Ref. 1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 236–241, February, 1998. 相似文献
994.
I. S. Belostotskaya V. B. Vol'eva N. L. Komissarova M. O. Dekaprilevich V. N. Khrustalev A. Yu. Karmilov V. V. Ershov 《Russian Chemical Bulletin》1997,46(7):1272-1280
Oxidative transformations of 2-dialkylaminomethyl-4,6-di-tert-butylphenols depend on the nature of the oxidant, the character of the substituents at the nitrogen atom, and the medium.
A mechanism of the oxidation of these compounds is suggested. The molecular structure of the compound obtained as a result
of oxidative trimerization of 2-dimethylaminomethyl-4,6-di-tert-butylphenol was established by X-ray structural analysis.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1328–1335, July, 1997. 相似文献
995.
A. G. Tozhibaev K. K. Turgunov B. Tashkhodzhaev Kh. M. Shakhidoyatov 《Chemistry of Natural Compounds》2006,42(3):340-344
The structures of deoxypeganine (DOP) hydrochloride and oxalate were solved by x-ray structure analysis. An infinite chain
along the crystallographic c axis was formed in the crystal structure of DOP oxalate. A molecular framework consisting of
Cl anions and DOP cation protonated at N1 was found in the structure of unhydrated DOP hydrochloride. The molecular packing
of the “host” (DOP cation) was pseudoisostructural in the studied ion-molecular crystals but differed from other known DOP
salts. The “guest” molecules (acid anions) in the studied and known DOP salts formed different intermolecular contacts.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 280–283, May–June, 2006. 相似文献
996.
Keller Hildegard Langer Elisabeth Lehner Harald Derflinger Gerhard 《Theoretical chemistry accounts》1978,49(2):93-100
The Algebraic Theory of Chirality Functions is derived by means of exclusively qualitative considerations. Hence, the significance of quantitative results is questionable. Moreover the construction of “Näherungsansätze” (”Approximation-Ansatz”), which may be interpreted as semiempirical methods, is achieved on the basis of plausibility and mathematical simplicity. Since physical arguments are not included, the consistency or inconsistency of “Näherungsansätze” with experimental results do not justify direct physical conclusions. 相似文献
997.
Apparent molal heat capacities
of some piperidine, morpholine, and piperazine derivatives in aqueous solution have been determined by adiabatic calorimetry
in the temperature range 20–55°C and in the molality range 0.2–1m. Comparison of experimental
values with those calculated through group contributions, found for monofunctional compounds, indicates strong interactions
between the hydrophilic centers. An interpretation is given of the possible mechanism of this interaction. Also, values of
ΔC
p
for the addition reaction of proton to nitrogen centers of mono- and bifunctional organic compounds are examined. 相似文献
998.
原子转移自由基聚合原位合成温敏性微球 总被引:1,自引:0,他引:1
以过硫酸钾为引发剂、丙酮-水[V(丙酮)∶V(水)=4∶6]的混合溶剂为反应介质, 在少量二乙烯苯存在的条件下使苯乙烯(St)和对氯甲基苯乙烯(CMSt)进行无皂乳液共聚反应, 得到了粒径大小均匀的交联型聚苯乙烯(PSt)微球, 由X射线光电子能谱对表面组分测定发现: CMSt上的氯原子在聚合过程中富集于交联微球的表面. 以此交联型PSt微球为原子转移自由基聚合(ATRP)的引发剂, 在22 ℃下引发N-异丙基丙烯酰胺(NIPAAm)进行原位ATRP反应, 得到了表面原子转移自由基聚合接枝的交联聚苯乙烯(PNIPAAm-g-PSt)温敏性微球. 借助傅立叶变换红外光谱、差示扫描量热仪、扫描电子显微镜及激光光散射仪等对PNIPAAm-g-PSt的结构、相转变温度、形态及不同温度下的粒径变化进行了测定, 结果表明NIPAAm单体成功地原位ATRP接枝在交联PSt微球的表面, 接枝微球的球形更规整, 在水中的相转变温度约为32 ℃, 具有明显的温度敏感性. 相似文献
999.
Ab initio calculations of the orbital and the ground state energies of some open- and closed-shell atoms over Slater type orbitals with quantum numbers integer and Slater type orbitals with quantum numbers noninteger have been performed. In order to increase the efficiency of these calculations the atomic two-electron integrals were expressed in terms of incomplete beta function. Results were observed to be in good agreement with the literature. 相似文献
1000.
用杂化密度泛函B3LYP方法研究了(AB)8(AB=BN,AlP,GaAs,InSb)团簇环形结构的平衡几何构型、电子结构、振动特性以及极化率。计算结果表明,(AB)8团簇的双层环状结构中,每个A(B)原子都与3个B(A)原子成键,且Ⅴ族元素的原子比Ⅲ族元素的原子更接近团簇中心,(BN)8、(AlP)8、(GaAs)8、(InSb)8的平均极化率依次增大,IR和Raman谱峰发生红移。另外,讨论了热力学稳定性和动力学稳定性的变化。 相似文献