Search results for "Carbon atom"
showing 8 items of 8 documents
Structure and Phase Transitions in Ethylenediammonium Dichloride and its Salts with Antimony Trichloride
2000
During the mixing of ethylenediammonium dichloride and antimony trichloride except of reported earlier [NH3(CH2)2NH3]5(Sb2Cl11)2 · 4 H2O a new salt [NH3(CH2)2NH3](SbCl4)2 was obtained. The crystals are monoclinic at 295 K, space group C2/m, a = 13.829(3), b = 7.408(1), c = 7.588(2) A; β = 103.18(3)°; V = 756.9(3) A3; Z = 2; dc = 2.585, dm = 2.56(2) g · cm–3. The structure consists of anionic sublattice built of Sb2Cl82– units composed of two SbCl52– square pyramids connected by edge. The ethylenediammonium cations are located in anionic cavities. The cations are disordered. Each methylene carbon atom is split between two positions. The X-ray diffraction, DSC, TGA and dilatometric methods we…
Synthesis of Multisubstituted 1,4-Dihydrobenzoxazin-2-ones through a One-Pot Nucleophilic N-Alkylation/C-Alkylation of Cyclic α-Imino Esters
2017
A nucleophilic N-alkylation of 2-oxobenzoxazine-2-carboxylates with organozinc reagents with good selectivities and in moderate to good yields is described. Moreover, the synthesis of multisubstituted 1,4-dihydrobenzoxazine-2-ones bearing a tetrasubstituted carbon atom via a one-pot N-alkylation/C-alkylation reactions is reported.
Effect of electron-withdrawing substituents on the electrophilicity of carbonyl carbons
2005
Indexación: Scopus The substituent effects on the carbonyl carbon atom for a series of twelve substituted phenyl acetates have been rationalized using a global electrophilicity index. This index is linearly correlated with the experimental reaction rate coefficients. We found that, in contrast to the proposed interpretation based on experimental 13C NMR chemical shifts and ground state destabilization calculations, the electrophilicity of carbonyl compounds increases due to the effect promoted by electron-withdrawing groups in these systems. https://www.sciencedirect.com/science/article/pii/S0040402004018046?via%3Dihub
Stanislao Cannizzaro and the Development of Chemistry in Palermo from 1862 to 1871
2009
Stanislao Cannizzaro worked at Palermo University for about ten years. There he managed to establish a modern and well-equipped chemical laboratory. His international fame attracted co-workers even from abroad: Naquet, Lieben, and Körner came to Palermo to work with him. This greatly improved the quality of teaching and of research in Palermo, which became a worldwide acknowledged center of chemical culture. In Palermo, atomic-molecular theory was extensively taught and research was carried out on chemical atomicity (valence) and spatial structures of both aliphatic and aromatic organic molecules: Körner found the relative positions of substituent groups on the benzene ring, Paternò proved …
Calix[4]arenes with alkylidene bridges, synthesis and conformational properties
1994
Abstract Calix[4]arenes with one or two alkylidene bridges were synthesized by “2+2” fragment condensation. As predicted by molecular mechanics calculations aliphatic residues at the bridging carbon atom(s) prefer the equatorial position.
What Is the Limit of Atom Encapsulation for Icosahedral Carboranes?
2015
The stability of endohedral carboranes X@{1,n-C2B10H12} (X = Li(+), Be(2+); n = 2, 7, 12) and X@{CB11H12(-)} (X = Li(+), Be(2+)) is studied using electronic structure calculations with the B3LYP/6-311+G(d,p) model. Our calculations suggest that all endohedral compounds are local energy minima; for the exohedral complexes X···cage, the global energy minimum always corresponds to the X atom above a triangular face of the icosahedron. In the latter the X atom is furthest apart from the carbon atoms of the cage. As opposite to exohedral {Be(2+)···cage} complexes, no global energy minima were found for exohedral complexes {Li(+)···cage} whereby a carbon atom is present in the triangular face of …
ChemInform Abstract: Synthesis of Functionalized Indoles with a Trifluoromethyl-Substituted Stereogenic Tertiary Carbon Atom Through an Enantioselect…
2010
Chiral complexes of BINOL-based ligands with zirconium tert-butoxide catalyze the Friedel-Crafts alkylation reaction of indoles with beta-trifluoromethyl-alpha,beta-unsaturated ketones to give functionalized indoles with an asymmetric tertiary carbon center attached to a trifluoromethyl group. The reaction can be applied to a large number of substituted alpha-trifluoromethyl enones and substituted indoles. The expected products were obtained with good yields and ees of up to 99%.
5-Substituted 4,5-Dihydro-1,2,4-triazin-3(2H)-ones from the Unprecedented Reaction between α-N-Protected Amino Acid Hydrazides and NaBH4
2006
α-N-Protected amino acid hydrazides (1) readily reacted with NaBH4 to afford 5-substituted 4,5-dihydro-1,2,4-triazin-3(2H)-one derivatives 2 in good yields. Unfortunately, the reaction caused partial racemization at the α-amino acidic carbon atom of the starting hydrazide. A mechanism, supported by experimental evidence, has been proposed in an attempt to explain this to date unprecedented reaction. The structure of compounds 2 was confirmed by X-ray structural analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)