Search results for "chemical science"
showing 10 items of 9771 documents
Poly[[tetramethanolbis[4-oxo-3-(pyridin-4-yl)-1-(2,4,6-trichlorophenyl)-4,5-dihydro-1H-pyrazolo[3,4-d]pyrimidin-6-olato]disodium]–diethyl ether–metha…
2016
In the title compound, [Na2(C16H7Cl3N5O2)2(CH3OH)4]·C4H10O·2CH3OH, the central pyrazolo[3,4-d]pyrimidine system makes dihedral angles of 82.98 (7)° with the trichlorophenyl ring and 13.11 (15)° with the pyridine ring. The sodium ion has an octahedral environment, being coordinated by four methanol molecules and one O and one N atom of two different heterocyclic ring systems.
(E)-1-(Pyridin-4-yl)propan-1-one O-tosyl oxime
2017
The title compound, C15H16N2O3S, was obtained by the reaction of (E)-1-(pyridin-4-yl)propan-1-one oxime andpara-toluenesulfonic acid. The pyridine ring makes a dihedral angle of 54.70 (10)° with the benzene ring. In the crystal, molecules are linked by C—H...O hydrogen bonds, forming a chain along thec-axis direction.
Crystal structure of the pyridine–diiodine (1/1) adduct
2015
In the title adduct, C5H5N·I2, the N—I distance [2.424 (8) Å] is remarkably shorter than the sum of the van der Waals radii. The line through the I atoms forms an angle of 78.39 (16)° with the normal to the pyridine ring.
3-(2,4-Difluorophenyl)-1-(pyridin-4-yl)benzo[4,5]imidazo[1,2-d][1,2,4]triazin-4(3H)-one
2016
In the title compound, C20H11F2N5O, the central 13-membered ring system (r.m.s. deviation = 0.028 Å) makes a dihedral angle of 53.13 (7)° with the difluorophenyl ring and 79.98 (7)° with the pyridine ring. The crystal packing features aromatic π–π interactions between the 13-membered rings [shortest distance between ring centroids = 3.5682 (8) Å].
Halogen Bonds in 2,5-Dihalopyridine-Copper(I) Halide Coordination Polymers
2019
Two series of 2,5-dihalopyridine-Cu(I)A (A = I, Br) complexes based on 2-X-5-iodopyridine and 2-X-5-bromopyridine (X = F, Cl, Br and I) are characterized by using single-crystal X-ray diffraction analysis to examine the nature of C2&minus
(2-Pyridyl)sulfonyl Groups for ortho -Directing Palladium- Catalyzed Carbon-Halogen Bond Formation at Functionalized Arenes
2017
International audience; We describe an efficient palladium-catalyzed selective C-H ortho-monohalogenation (X=I, Br, Cl, F) of various functionalized (2-pyridyl) aryl-sulfones. ortho-, meta-and para-functionalization is tolerated at the arene group which undergoes C-H halogenation. Some modifications are also possible on the 2-(arylsulfonyl) heteroaryl directing groups. A comparison of the halogenation efficiency suggests that bromination is the practical method of choice, while chlorination and fluorination are possible but more challenging. Under forcing conditions ortho-dihalogenation can also be achieved.
Pyrolytic behavior of lignocellulosic-based polysaccharides
2018
The thermochemical behavior of cellulose, glucomannan, and xylan was investigated by pyrolysis–gas chromatographymass spectrometry (Py-GC/MS). In each case, major GC-amenable condensable products were classified into several compound groups, and the formation of these monomer-related fragments from the model substance samples was determined at 500, 600, and 700 C with a residence time of 5 s and 20 s. The results revealed that despite some general formation trends, no compound group was selectively formed at certain temperatures. Of the 11 product groups, the primary ones, including lactone, furan, and cyclopentenone derivatives, accounted for 72–85% (from cellulose), 86–90% (from glucomann…
High-affinity and selective detection of pyrophosphate in water by a resorcinarene salt receptor
2017
N-Alkyl ammonium resorcinarenes selectively bind pyrophosphate in pure water with an exceptionally high binding constant of up to 1.60 × 107 M–1, three orders of magnitude higher than ATP.
Transferts de matière au travers des emballages au contact de produits alimentaires
2009
Le point sur des recherches dans le domaine des transferts de matière au travers des emballages : impact sur la qualité du produit, causes de ces transferts.
Combined Spectroscopic and TD-DFT Analysis to Elucidate Substituent and Acidochromic Effects in Organic Dyes: A Case Study on Amino- versus Nitro-Sub…
2020
Made available in DSpace on 2020-12-12T01:33:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 A combined spectroscopic and TD-DFT case study was performed, to identify a robust method to calculate the complex near UV/Vis absorption spectra of various amino- vs. nitro-substituted 2,4-diphenylquinolines, which vary strongly under neutral and successively acidic conditions. For this, different DFT functionals were tested for geometry optimization and the TD part to calculate the neutral and different protonated species in a fast screening approach, i. e. using single point calculations in an implicit solvent. Offset-corrected M06HF, hitherto only applied to polymers, was identif…