Search results for " hydrogen"
showing 10 items of 319 documents
Applications and stereoselective syntheses of P-chirogenic phosphorus compounds.
2016
International audience; Phosphorus compounds bearing chirality on the P-center are usually qualified as P-chirogenic or P-stereogenic. This chemical class concerns natural products, agrochemistry, molecular materials, biology and pharmacy, although it is certainly in coordination chemistry and in asymmetric catalysis using chiral transition metal complexes that P-chirogenic phosphorus compounds are the most used. The chiral phosphine ligands and their uses in asymmetric metal-catalyzed reactions have been widely reviewed in literature. However, an overview covering the applications as well as the stereoselective syntheses of all classes of phosphorus compounds has not yet been provided. Thi…
Chiroptical Phenomena in Reverse Micelles: The Case of (1R,2S)- Dodecyl (2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium Bromide (DMEB)
2014
(1R,2S)-Dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) aggregates dispersed in carbon tetrachloride have been investigated by Fourier transform infrared (FT-IR), vibrational circular dichroism (VCD) and 1H nuclear magnetic resonance (NMR) spectroscopy at various surfactant concentration and water-to-surfactant molar ratio. Experimental data indicate that, even at the lowest investigated concentration and in absence of added water, DMEBmolecules associate in supramolecular assemblies. At higherDMEBconcentration the aggregates can confine watermolecules,making it plausible to think thatDMEB form reverse micelles and that watermolecules are quite uniformly distributed…
Conformational investigation of α,β‐dehydropeptides. XV: N‐acetyl‐α,β‐dehydroamino acid N ′N ′‐dimethylamides: conformational properties from infrare…
2005
The FTIR spectra were analysed in the region of the nu(s)(N-H), AI(C=O) and nu(s)(Calpha=Cbeta) bands for a series of Ac-DeltaXaa-NMe2, where DeltaXaa = DeltaAla, (Z)-DeltaAbu, (Z)-DeltaLeu, (Z)-DeltaPhe and DeltaVal, to determine a predominant solution conformation of these alpha,beta-dehydropeptide-related molecules. Measurements were taken in CCl4, DCM and MeCN solutions. In the same way, spectra of saturated analogues Ac-Xaa-NMe2, where Xaa = Ala, Abu, Leu, Phe and Val, were investigated. To help interpret the spectroscopic results, conformational maps were calculated by the B3LYP/6-31+G** method. Also, the relative energies of all conformers of the dehydro compounds in vacuo as well as…
Crystal structure of (E)-4-methyl-N-{2-[2-(4-nitrobenzylidene)hydrazin-1-yl]-2-oxoethyl}benzenesulfonamideN,N-dimethylformamide monosolvate
2017
The molecule of the title Schiff base compound, C16H16N4O5S·C3H7NO, displays atransconformation with respect to the C=N double bond. The C—N and N—N bonds are relatively short compared to their normal bond lengths, indicating some degree of delocalization in the molecule. The molecule is bent at the S atom, with an S—N—C—C torsion angle of 164.48 (11)°. The dihedral angle between the two aromatic rings is 84.594 (7)°. Intermolecular N—H...O and C —H...O hydrogen bonds connect centrosymmetrically related molecules into dimers forming rings ofR33(11) andR22(10) graph-set motif stacked along theaaxis into a columnar arrangement. The molecular columns are further linked into a three-dimensional…
Fecal Calprotectin in Self-Reported Milk Intolerance: Not Only Lactose Intolerance
2023
The hypothesis is that inflammatory/allergic conditions should be considered in self-reported milk intolerance (SRMI) patients who test negative and/or are asymptomatic at Lactose Hydrogen Breath Test (LHBT). We analyzed fecal calprotectin (FCP) values in SRMI patients to investigate the frequency of a “positive” intestinal inflammation marker and its correlation with lactose tolerance/intolerance. Data from 329 SRMI patients were retrospectively analyzed; according to the positive/negative results (maldigester/digester) and the presence/absence of symptoms reported during LHBT (intolerant/tolerant), patients were divided into: ‘lactose tolerants’ (n. 104), ‘ma…
Crystal structure of 2-{[1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-yloxy]carbonyl}benzoic acid
2014
In the title compound, C15H15N3O6, the dihedral angle between the planes of the benzene and imidazole rings is 34.93 (10)°. An intramolecular C—H...O hydrogen bond is observed. In the crystal, O—H...N hydrogen bonds link the molecules into chains parallel to thecaxis.
Crystal structure and Hirshfeld surface analysis of dimethyl (1R*, 3aS*, 3a(1)R*, 6aS*, 9R*, 9aS*)-3a(1),5,6,9a-tetrahydro-1H,4H,9H-1,3a:6a,9-diepoxy…
2019
The title diepoxyphenalene derivative, C17H18O6, comprises a fused cyclic system containing four five-membered rings (two dihydrofuran and two tetrahydrofuran) and one six-membered ring (cyclohexane). The five-membered dihydrofuran and tetrahydrofuran rings adopt envelope conformations, and the six-membered cyclohexane ring adopts a distorted chair conformation. Two methyl carboxylate groups occupy adjacent positions (2- and 3-) on a tetrahydrofuran ring. In the crystal, two pairs of C-H center dot center dot center dot O hydrogen bonds link the molecules to form inversion dimers, enclosing two R-2(2)(6) ring motifs, that stack along the a-axis direction and are arranged in layers parallel …
Crystal structure of 2-(adamantan-1-yl)-5-(4-bromophenyl)-1,3,4-oxadiazole
2014
In the title molecule, C18H19BrN2O, the benzene ring is inclined to the oxadiazole ring by 10.44 (8)°. In the crystal, C—H...π interactions link the molecules in a head-to-tail fashion, forming chains extending along thec-axis direction. The chains are further connected by π–π stacking interactions, with centroid–centroid distances of 3.6385 (7) Å, forming layers parallel to thebcplane.
Crystal structure of N,N,N′,N′,N′′,N′′-hexamethylguanidinium cyanate 1.5-hydrate
2015
The title hydrated salt, C7H18N3+·OCN−.1.5H2O, was synthesized starting fromN,N,N′,N′,N′′,N′′-hexamethylguanidinium chloride by a twofold anion-exchange reaction. The asymmetric unit contains two cations, two cyanate anions and three water molecules. One cation shows orientational disorder and two sets of N-atom positions were found related by a 60° rotation, with an occupancy ratio of 0.852 (6):0.148 (6). The C—N bond lengths in both guanidinium ions range from 1.329 (2) to 1.358 (10) Å, indicating double-bond character, pointing towards charge delocalization within the NCN planes. Strong O—H...N hydrogen bonds between the crystal water molecules and the cyanate ions and strong O—H...O hyd…
Crystal structure of chlorido(2-{1-[2-(4-chlorophenyl)hydrazin-1-ylidene-κN]ethyl}pyridine-κN)(η5-pentamethylcyclopentadienyl)rhodium(III) chloride
2015
The title compound, [Rh(η5-C5Me5)Cl(C13H12ClN3)]Cl, is chiral at the metal and crystallizes as a racemate. Upon coordination, the hydrazinylidenepyridine ligand is non-planar, an angle of 54.42 (7)° being observed between the pyridine ring and the aromatic ring of the [2-(4-chlorophenyl)hydrazin-1-ylidene]ethyl group.