共查询到20条相似文献,搜索用时 31 毫秒
1.
Valentin Vankov Iliev 《Journal of mathematical chemistry》2010,47(1):52-61
In this paper, a mathematical characterization of Lunn–Senior’s groups of univalent substitution isomerism of the linear alkanes,
under some natural assumptions that reflect their common properties, is given. For each linear alkane, the number of its monosubstitution
derivatives, its di-substitution derivatives, and its tri-substitution derivatives as linear, quadratic, and cubic polynomial
expressions, respectively, in their number, is obtained. In principle, the number of derivatives of a given linear alkane
with any particular composition can be established. The same explicit expressions for the case of k-substitution homogeneous derivatives of the linear alkanes are obtained by Balasubramanian (Theoret. Chim. Acta (Berl.) 51:37,
1979). 相似文献
2.
François Le Moigne Rene Dabard Maryvonne Le Plouzennec 《Journal of organometallic chemistry》1976,122(3):365-376
The photochemical substitution, by various phosphines or phosphites, of the carbonyl ligands of derivatives of cymantrene has been studied, giving evidence of the effect of the electron density on the metal for mono- or di-substitution. Optically active derivatives which are chiral at manganese have been synthesized and their enantiomeric stability ascertained. 相似文献
3.
Crosslinked co-poly/styrene-4-vinyl(N-hexylpyridinium bromide) was converted with bromine or chlorine to insoluble polymer supported complexes
or
respectively, and their reactivity studied in reactions with various aromatic molecules. Reagent
was found in all cases to be milder than reagent
and regiospecifically transformed alkoxy and amino substituted benzenes (
) into 4-bromo derivatives, while corresponding reactions with
resulted in dibromo derivatives. Several benzoheterocyclic molecules were converted with
to substitution or addition products, i.e. 2,3-dibromo-N-methylpyrrole, 3-bromobenzo/b/thiophene, and 2,3-dibromo-2,3-dihydrobenzofuran. In the series of ortho-alkyl disubstituted benzene derivatives, i.e. o-xylene, indane, and tetraline, where the Mills-Nixon effect was established with various electrophilic reagents, bromination reactions with
showed higher β-selectivity than the corresponding reactions with bromine. The rate of bromination in various alkyl substituted benzenes with reagent
depended on the magnitude of the alkyl group, as well as the para/ortho regioselectivity, amounting to 100% in the case of tert-butylbenzene. 相似文献
4.
New derivatives of 4-amino [3,4-d] pyrazolo pyrimidine have been prepared. Mono, di- and tri-substitution products are characterised by unequivocal synthesis. Several compounds are being tested for possible carcinostatic activity. 相似文献
5.
Abstract Cellulose carbamate and ester derivatives were synthesized in homogeneous solutions of lithium chloride (LiCl)/N,N-dimemyl-acetamide (DMAc) by the reaction of cellulose with ethyl 4-isocyanatobenzoate and the activated esters of N,N-dimethyl-aminobenzoic acids. Comparative reactions were performed with phenyl isocyanate and the activated ester of benzoic acid. All reactions were followed spectroscopically by FTIR, 1H NMR, and 13C NMR. Degrees of substitution were calculated utilizing UV spectroscopy. The isocyanate reactions are facile allowing controllable degrees of substitution and high yields. By contrast, the activated ester pathway inherently results in lower degrees of substitution and lower yields due in part to undesirable side reactions. 相似文献
6.
Symmetrical star-shaped molecules with carborane clusters on the periphery have been synthesized in good yields via silicon tetrachloride mediated cyclotrimerization reactions of 9-benzyl derivatives of carboranes with acetyl group substitution on the benzene ring. Facile functionalization of these symmetrical core structures with 1-iodoheptane and trivinylchlorosilane produce compounds which could be used as liquid crystalline substances and precursors for synthesis of higher order carbosilane dendrons. 相似文献
7.
V. P. Zvolinskii M. E. Perel'son Yu. N. Sheinker 《Theoretical and Experimental Chemistry》1972,5(2):106-110
The electronic structure of 2- and 4-hydroxypyridines and their chemical reaction capacity have been studied following the pattern of aromatic substitution in neutral, acid, and alkaline media within the framework of the Hückel approximation of the LCAO MO method. The reaction capacity indexes were calculated for both isolated and reacting molecules. It was shown that the calculated magnitudes agree well with previously recorded experimental data. The results obtained may serve to predict the direction of aromatic substitution reactions not yet studied within the hydroxypyridines series and their derivatives.The authors thank A. V. Tutkevich for kindly submitting the calculations program. 相似文献
8.
Lucas Kistner Erik Filbeck Patrick Ihle David Bučak Gasser Sebastian W. H. Häussermann Dario Kowatsch Dr. Elisabeth Kaifer Prof. Hans-Jörg Himmel 《European journal of organic chemistry》2023,26(11):e202300038
Starting with diboranes with two electron-rich bridging bicyclic guanidinate substituents, we report in this work the rational synthesis of new dicationic symmetrically- and unsymmetrically-substituted diboranes in SN1-type substitution reactions in which triflato or bromo substituents are replaced by neutral Lewis bases. The scope of such substitution reactions and their rate are analyzed with different pyridine derivatives of variable Lewis basicity. The first substitution step, leading to a monocationic diborane with one anionic substituent (triflate or bromide) and one neutral Lewis base, proceeds much faster than the second substitution step leading to a dicationic diborane with two neutral Lewis bases. The different time scales for the substitution steps could be used to conveniently synthesize in one-pot reactions several dicationic, unsymmetrically-substituted diboranes with two different neutral Lewis bases. 相似文献
9.
10.
The 2,3,4-tri-toluenesulfonate ester derivatives of the methyl pyranosides of l-arabinose, d-ribose, d-lyxose, and d-xylose have been prepared, and their substitution reactions with various nucleophiles have been examined. For arabinose, xylose, and ribose, highly regioselective monosubstitutions were observed with benzoate, nitrite, and azide anions. These reactions have led to short and simple routes from d-xylose to l-arabinose derivatives, from l-arabinose to d-xylose derivatives, and from d-ribose to l-lyxose derivatives. The tritosylate derived from methyl alpha-d-lyxopyranoside was unreactive toward nucleophilic substitution reactions, giving instead a dihydropyran product arising from an initial E2 elimination reaction of the 2-tosylate. 相似文献
11.
Equilibrium ground state geometry configurations and their relevant electronic properties of four experimentally reported
asymmetric spirosilabifluorene derivatives are calculated by the HF(DFT)/6-31G(d) method. Their excited state geometries are
investigated using the CIS/6-31G(d) method. The absorption and emission spectra are evaluated using the TD-B3LYP/6-31G(d)
and TD-PBE0/6-31+G(d) levels both in gas phase and CHCl3 solvent. Our results show an excellent agreement with the experimental data on their optical properties. To predict the substitution
effect, the H/R (R = –NO2, –CN, –NH2 and –OCH3) substituted symmetric and asymmetric spirosilabifluorene derivatives are also investigated, and the optical properties of
H/R substituted derivatives are predicted in gas phase and CHCl3 solvent. In comparison with the parent compound, significant red-shift is predicted for the emission spectra of the di-substituted
symmetric derivatives with –NH2 (96 nm), –OCH3 (61 nm) and the push–pull (containing both –NH2 and –NO2) derivative (56 nm). It is found that the performance and the optical properties of these derivatives can be improved by
adding push–pull substitutents. The largest change in the electronic and optical properties of this system can be obtained
upon symmetric di-substitution among mono-, di-, tri- and tetra-substitutions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
The infrared spectra of a number of esters and free acids in the cholanic acid series have been examined with the aid of a special solvent system which overcomes the problem of solubility. Eleven absorption regions in the 9–12 μ region have been correlated with specific substitution on the steroid nucleus and side chain. In certain cases, perturbations were found when di- or tri-substitution occurred in rings A, B, andJor C. 相似文献
13.
V. V. Azatyan 《Kinetics and Catalysis》2002,43(2):149-164
A new class of fast thermal gas-phase reactions of the direct substitution of atoms in polyatomic molecules by atomic reactants is discovered. The Arrhenius parameters are determined for the reactions of atomic deuterium with a number of hydrogen-containing compounds, occurring via the direct substitution of hydrogen atoms and via the abstraction of hydrogen atoms. Fast substitution of alkali metal atoms from the crystals of their salts for the reaction chain carriers of hydrogen flames is found. The importance of reactions of these types in chain combustion is demonstrated. The kinetic isotope effects of hydrogen atom abstraction from hydrocarbon molecules by hydrogen and deuterium atoms are studied. A method for the kinetic studies of free atoms and radicals is developed, which takes into account the role of longitudinal diffusion in the jet and does not require the knowledge of the concentrations of atoms and radicals or the rate constants of other reactions. 相似文献
14.
The work utilized photoinduced electron transfer (PET) reactions to identify the preferred photoreaction route in molecules having juxtaposed α,β and β,γ-enones. Such process directly converted 2-hydroxyimino derivatives of 5-benzoylbicyclo[2.2.2]octenones to the corresponding bicyclo[3.2.1]octane derivatives. First evidence of Type B rearrangement in α,β-enones having acyl substitution at Cγ-position has been depicted in this work. In rigid mixed enones, this has been found to be generally the preferred photoreaction route. 相似文献
15.
4-(1-Haloalkyl)-3-nitrotetrahydrofurans, which are accessible by tandem oxidative oxa-Michael addition/radical cyclization/ligand transfer reactions, can be processed to diversely substituted tetrahydrofuran derivatives. Selective epimerization at the nitro function provides tetrahydrofuran diastereomers, which cannot be prepared by the tandem process. Intramolecular alkylations furnish interesting bridgehead nitro oxabicyclo[3.1.0]hexane derivatives in high yields. Intermolecular substitution reactions of the halide functions succeed only with nucleophiles, which are not basic enough to trigger intramolecular alkylations. The aryl substituent in 2-aryl-3-nitrotetrahydrofurans can be selectively oxidatively transformed to carboxylic acid derivatives using catalytic Ru(III) and NaIO4 without affecting the nitro group. Reduction and hydrogenation reactions provide differently substituted 3-aminotetrahydrofuran derivatives depending on the conditions with moderate to good chemoselectivity. 相似文献
16.
17.
Abstract— The photochemical reactions of benzophenone and acetophenone with purine and pyrimidine derivatives in aqueous solutions have been investigated by flash photolysis and steady-state experiments. Upon excitation of these two ketones in aqueous solutions, two transient species are observed: molecules in their triplet state and ketyl radicals. The triplet state lifetimes are 65 μsec for benzophenone and 125 μsec for acetophenone. The ketyl radicals disappear by a second order reaction, controlled by diffusion. In the presence of pyrimidine derivatives, the triplet state is quenched and the ketyl radical concentration is decreased without any change in its kinetics of disappearance. Ketone molecules in their triplet state react with purine derivatives leading to an increase in the yield of ketyl radicals due to H-atom abstraction from the purines. Steady-state experiments show that benzophenone and acetophenone irradiated in aqueous solution at wavelengths longer than 290 nm undergo photochemical reactions. The rate of these photochemical reactions is increased in the presence of pyrimidine derivatives and even more in the presence of purine derivatives. Following energy transfer from the triplet state of benzophenone to diketopyrimidines, cyclobutane dimers are formed. The energy transfer rate decreases in the order orotic acid > thymine > uracil. Benzophenone molecules in their triplet state can also react chemically with pyrimidine derivatives to give addition photoproducts. All these results are discussed with respect to photosensitized reactions in nucleic acids involving ketones as sensitizers. 相似文献
18.
19.
碳十硼烷及其衍生物的反应性及应用 总被引:1,自引:0,他引:1
碳十硼烷(C2B10H12)是由2个C原子和10个B原子组成的二十面体笼状结构大分子,有邻位、间位和对位三种异构体。碳十硼烷庞大的体积以及类芳香族三维刚性结构使它具有优异的高温稳定性和化学稳定性,良好的溶解性使其具有广泛而灵活的应用。本文总结了近年来碳十硼烷和碳十硼烷衍生物在C原子、B原子上的化学反应性以及在环加成和金属络合方面的研究。另外,由于碳十硼烷衍生物特殊的立体结构,优异的耐高温性、热氧化性及高硼含量,本文综述了碳十硼烷衍生物近年来在功能材料、催化剂及生物医药等多个领域的应用进展。 相似文献
20.
D. V. Korol'kov 《Russian Journal of General Chemistry》2002,72(4):523-535
The results of theoretical, experimental investigations on activation of small molecules on their coordination to cluster complexes of heavy transition metals with weak- and strong-field ligands are presented. Homogeneous catalytic redox reactions of the CO, N2, H2O molecules and the N3
- molecular anion in the presence of cluster complexes of low-valent molybdenum and rhenium are studies. The reaction mechanism is established. Three modifications of the homogeneous cluster catalysis of redox reactions of small molecules are described. 相似文献