Search results for "Reactivity"
showing 10 items of 880 documents
Monomere und polymere Succinimidoester von ω-Methacryloylaminosäuren, ihre Darstellung und ihre Reaktion mit Aminen
1978
Mit der in dieser Arbeit beschriebenen Synthese von ω-Methacryloylaminosaure-succinimidoestern (1) wurden Monomere erhalten, die leicht mit Methacrylamid copolymerisiert werden konnten. Die entstandenen Copolymeren, die als Trager fur Enzyme und Pharmaka verwendet werden konnen, tragen die selektiv mit Aminen reagierende Succinimidoester-Gruppe an einem “Spacerarm”. Die Reaktionsfahigkeit der neuen Monomeren gegenuber verschiedenen Aminen wurde untersucht. The synthesis of succinimido esters of ω-methacryloylaminocarboxylic acids affords monomers which can easily be copolymerized with methacrylamide. The resulting copolymers have a succinimido ester group fixed on a “spacer arm”, which reac…
A quantum chemical topological analysis of the c-c bond formation in organic reactions involving cationic species
2014
ELF topological analysis of the ionic Diels-Alder (I-DA) reaction between the N,N-dimethyliminium cation and cyclopentadiene (Cp) has been performed in order to characterise the C-C single bond formation. The C-C bond formation begins in the short range of 2.00-1.96 Åvia a C-to-C pseudoradical coupling between the most electrophilic center of the iminium cation and one of the two most nucleophilic centers of Cp. The electron density of the pseudoradical center generated at the most electrophilic carbon of the iminium cation comes mainly from the global charge transfer which takes place along the reaction. Analysis of the global reactivity indices indicates that the very high electrophilic c…
ChemInform Abstract: The Chemistry of Unsaturated Nitrogen-Heterocyclic Compounds Containing Carbonyl Groups
2010
Publisher Summary Most hydroxy-substituted azaheteroaromatic compounds exist predominately in the NH/carbonyl tautomeric form, and these compounds have been widely discussed. This chapter provides an overview of azaheteroaromatic compounds and I-azetin-4-ones—these are those azaheterocycles that contain in the ring at least one carbonyl group and one or two nitrogen atoms in the form of C=N or N=N bonds. Many of these compounds are unstable but their importance as reactive intermediates is established, and many of them could be used as synthons in the preparation of pharmacologically active compounds. The chapter describes the free existence of I-azetin-4-one and the nucleophilic substituti…
The Chemistry of Unsaturated Nitrogen–Heterocyclic Compounds Containing Carbonyl Groups
1993
Publisher Summary Most hydroxy-substituted azaheteroaromatic compounds exist predominately in the NH/carbonyl tautomeric form, and these compounds have been widely discussed. This chapter provides an overview of azaheteroaromatic compounds and I-azetin-4-ones—these are those azaheterocycles that contain in the ring at least one carbonyl group and one or two nitrogen atoms in the form of C=N or N=N bonds. Many of these compounds are unstable but their importance as reactive intermediates is established, and many of them could be used as synthons in the preparation of pharmacologically active compounds. The chapter describes the free existence of I-azetin-4-one and the nucleophilic substituti…
Linear free energyortho-correlations in the thiophene series. Part IX . Kinetics of esterification with diazodiphenylmethane of some 3-, 4-, and 5-su…
1981
The rate constants for the esterification of some 3-, 4-, and 5-substituted thiophene-2-carboxylic acids with diazodiphenylmethane in methanol at 25° have been measured. The reactivity of some para- and ortho-substituted benzoic acids has also been determined. Logarithmic kinetic constants for ortho-, meta-, and para-like substituted thiophene-2-carboxylic acids furnish an excellent linear free energy relationship when plotted versus Δpka (β 0.89, r 0.989, C.L. > 99.9%, n 18, i 0.04), thus confirming the peculiar behaviour of five-membered ring derivatives. The correlation with σH values offers an additional proof of the hyper-ortho character of the 2,3-relation in thiophene derivatives. pa…
Electrophilic substitution and cyclization of 2,2′-bis(N-methylindolyl): A simple access to potential protein kinase C inhibitor
1994
A strategy is described for the synthesis of functionalized and cyclized 2,2′-bisindolyl derivatives related to several basic systems of natural products. The starting 2,2′-bis(N-methylindolyl) (8) reacts with a variety of electrophiles and electrophilic dienophiles to furnish the novel, functionalized and cyclized bisindolyl derivatives 9–16. In addition, some reactivity and structural aspects are discussed; an X-ray crystallographic analysis of the 2,2′-bisindolyl 8 provided valuable information for the conformational analyses.
ChemInform Abstract: ortho Effect on the Nitrosation of the 2,3-Diphenyl-5-(2-methoxyphenyl)pyrrole.
1990
A comparison of the behaviour on the nitrosation of the isomers 5-(2-methoxyphenyl)- (1a) 5-(3-methoxyphenyl)- (1b) and 5-(4-methoxyphenyl)2,3-diphenylpyrroles (1c) carried out in the usual way with iso-amyl nitrite in a solution of sodium ethoxide in ethanol evidences that 1a is dramatically less reactive with respect to 1b and 1c. The different reactivity was ascribed to the occurrence of a strong hydrogen bond involving pyrrole NH and the ortho-methoxy group.
orthoeffect on the nitrosation of the 2,3-diphenyl-5(2-methoxyphenyl)pyrrole
1990
A comparison of the behaviour on the nitrosation of the isomers 5-(2-methoxyphenyl)- (1a) 5-(3-methoxyphenyl)- (1b) and 5-(4-methoxyphenyl)2,3-diphenylpyrroles (1c) carried out in the usual way with iso-amyl nitrite in a solution of sodium ethoxide in ethanol evidences that 1a is dramatically less reactive with respect to 1b and 1c. The different reactivity was ascribed to the occurrence of a strong hydrogen bond involving pyrrole NH and the ortho-methoxy group.
Understanding the reactivity of captodative ethylenes in polar cycloaddition reactions. A theoretical study
2008
The electrophilic/nucleophilic character of a series of captodative (CD) ethylenes involved in polar cycloaddition reactions has been studied using DFT methods at the B3LYP/6-31G(d) level of theory. The transition state structures for the electrophilic/nucleophilic interactions of two CD ethylenes toward a nucleophilically activated ethylene, 2-methylene-1,3-dioxolane, and an electrophilically activated ethylene, 1,1-dicyanoethyelene, have been studied, and their electronic structures have been characterized using both NBO and ELF methods. Analysis of the reactivity indexes of the CD ethylenes explains the reactivity of these species. While the electrophilicity of the molecules accounts for…
Synthesis and Properties of Some Simple Organotitanium Compounds
1986
Before embarking on a detailed discussion of the titanation of carbanions, synthetic and physical organic aspects of several typical organotitanium (IV) compounds shall be surveyed, including thermal stability, aggregation state, X-ray structural data and bond energies. Some of this information is useful in understanding reactivity and selectivity in reactions with organic substrates. Low valent Ti (II) and Ti (III) shall be mentioned only on passing; the interested reader is referred to reviews [1].