Prototropic Tautomerism and Some Features of the IR Spectra of 2-(3-Chromenyl)-1-hydroxyimidazoles

2019 ◽  
Vol 72 (9) ◽  
pp. 699 ◽  
Author(s):  
Polina A. Nikitina ◽  
Tatiana Yu. Koldaeva ◽  
Vitaly S. Mityanov ◽  
Vladimir S. Miroshnikov ◽  
Elizaveta I. Basanova ◽  
...  
Keyword(s):  
Solid State ◽  
Ir Spectra ◽  
Carbonyl Group ◽  
Tautomeric Form ◽  
Imidazole Ring ◽  
General Effect ◽  
Dmso Solution ◽  
Prototropic Tautomerism ◽  
Leading Role ◽  
Equilibrium Shift

Prototropic tautomerism of 2-(3-chromenyl)-1-hydroxyimidazoles with various substituents in the chromenyl moiety (1-hydroxyimidazole – imidazole N-oxide) was studied by means of 1H NMR and IR spectroscopies. It was demonstrated that in d6-DMSO solution, the substituents in the chromenyl ring have no influence on the equilibrium shift: the prevalence of the N-oxide tautomeric form is caused by the possibility of stabilization of the planar structure with the help of the carbonyl group in position 5 of the imidazole ring. In contrast, in the solid state the general effect of the chromenyl substituent in position 2 of imidazole plays the leading role. The increase in general electron-withdrawing effect of the chromenyl moiety leads to the prevalence of the imidazole N-oxide tautomer.

Synthesis and Study of Prototropic Tautomerism of 2-(2-Furyl)-1-hydroxyimidazoles

2020 ◽  
Vol 73 (11) ◽  
pp. 1098
Author(s):  
Polina A. Nikitina ◽  
Tatiana Yu. Koldaeva ◽  
Marina A. Zakharko ◽  
Valery P. Perevalov
Keyword(s):  
Carbonyl Group ◽  
13C Nmr ◽  
Tautomeric Form ◽  
Prototropic Tautomerism ◽  
Deuterated Chloroform ◽  
Model Compounds ◽  
Imidazole Derivatives

Novel 2-(2-furyl)imidazole derivatives were synthesised. 2-(2-Furyl)-1-methoxyimidazoles and 2-(2-furyl)-1-methylimidazole 3-oxides were used as model compounds in the study of the prototropic tautomerism of 2-(2-furyl)-1-hydroxyimidazoles by means of 1H, 13C NMR and UV/vis spectroscopies. It was demonstrated that the interaction of the π-excessive furyl moiety with an electron-withdrawing carbonyl group in position 5 of imidazole stabilised the N-hydroxy tautomeric form in both deuterated chloroform and d6-DMSO. In ethanol the N-oxide tautomer is also present along with the prevailing N-hydroxyimidazole.

Circular dichroism and infrared study of β-turn formation in repeat peptides of elastin

1987 ◽  
Vol 52 (5) ◽  
pp. 1356-1361
Author(s):  
S. Abdel Rahman ◽  
M. Elsafty ◽  
A. Hattaba
Keyword(s):  
Circular Dichroism ◽  
Solid State ◽  
Ir Spectra ◽  
Chain Length ◽  
Room Temperature ◽  
Infrared Study ◽  
Feature Characteristic ◽  
C 50 ◽  
The Stability ◽  
Circular Dichroïsm

The conformation of elastin-like peptides Boc-Ala-Pro-Gly-Val-APEGM, Boc-Ala-Pro-Gly-Val-Gly-Val-APEGM, Boc-Ala-Pro-Gly-Val-Ala-Pro-Gly-Val-Gly-Val-APEGM, Boc-Ala-Pro-Gly-Val-Gly-Val-Ala-Pro-Gly-Val-Gly-Val-APEGM were examined in solution using circular dichroism at 30 °C, 50 °C, and 70 °C and in solid state by IR at room temperature. The studies show that the β-turn is a significant conformational feature for peptides under investigation in solution at 30 °C and 50 °C, but at 70 °C the tetra, hexa, and decapeptides show the CD feature characteristic of the β-structure while the dodecapeptide spectra show the presence of β-turn which indicates the stability of the β-turn at this chain length. The IR spectra show that in the solid state at room temperature all investigated peptides assume essentially a β-turn except the tetrapeptide which present evidence of antiparallel β-structure. The β-turn contribution in the IR spectra increases with the increase of the chain length of the peptide.

Complexation of 7-azaindole by the methylmercury(II) cation

1992 ◽  
Vol 70 (12) ◽  
pp. 2914-2921 ◽  
Author(s):  
Nathalie Dufour ◽  
Anne-Marie Lebuis ◽  
Marie-Claude Corbeil ◽  
André L. Beauchamp ◽  
Pascal Dufour ◽  
...  
Keyword(s):  
Solid State ◽  
Nmr Spectra ◽  
Pyridine Ring ◽  
Coordination Mode ◽  
Pyrrole Ring ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Major Influence ◽  
Large Displacements ◽  
Dmso Solution

Complexes of the types [CH3Hg(aza)], [CH3Hg(Haza)]X, and [(CH3Hg)2(aza)]X are obtained by reacting CH3HgOH and/or CH3HgX (X = NO3, ClO4) with 7-azaindole (Haza). The weakly acidic N1-H proton on the pyrrole ring is displaced by the hydroxide, whereas the perchlorate and nitrate salts lead to CH3Hg+ coordination to the N7 lone pair on the pyridine ring. Detailed analysis of the infrared spectra of the complexes and their N-deuterated derivatives provides diagnostic regions for eventual prediction of the coordination mode in other systems. All compounds are characterized by means of 1H, 13C, and 199Hg NMR spectra in DMSO solution and solid-state CP-MAS 13C spectra. Comparison of the solution and solid-state 13C spectra show that the species present in the solids remain undissociated in DMSO. Each type of complex can be identified from a characteristic pattern of large displacements of the ligand 13C signals. The 1H spectra are less informative because substitution of the N1-H proton by CH3Hg+ induces only minor shifts. Metal solvation appears to have a major influence on the 13C and 199Hg chemical shifts of the CH3Hg+ groups.

Etude par spectrométrie infrarouge de l'action de solvants aprotiques sur l'association ester–eau et ester–Ba2+. Discussion du rôle catalytique du solvant et de l'ion Ba2+ dans l'hydrolyse alcaline du propionate de methyle

1979 ◽  
Vol 57 (4) ◽  
pp. 400-403 ◽  
Author(s):  
Anne Le Narvor ◽  
Pierre Saumagne
Keyword(s):  
Ir Spectra ◽  
Charge Density ◽  
Carbonyl Group ◽  
Alkaline Hydrolysis ◽  
Experimental Results ◽  
Methyl Propionate ◽  
Orbital Control ◽  
Different Types ◽  
Kinetics Of ◽  
Better Than

The ir spectra of mixtures of methyl propionate/water and methyl propionate/Ba2+ in dimethylsulfoxide and in acetonitrile have been recorded in the region of the νCO mode of the ester. Evidence is presented to indicate the presence of different types of complexes; their concentration was determined as a function of the composition of the medium. The spectroscopic results are compared to those from the kinetics of the alkaline hydrolysis in the same conditions. It is demonstrated that the orbital control explains the experimental results better than does the charge density on the carbon of the carbonyl group. [Journal translation]

Evaluation of solid state of rice flours produced by different milling processes using ATR-FTIR spectroscopy

2021 ◽  
Author(s):  
Daitaro Ishikawa ◽  
Jiamin Yang ◽  
Chiaki Ichikawa ◽  
Tomoyuki Fujii
Keyword(s):  
Solid State ◽  
Ir Spectra ◽  
Ftir Spectroscopy ◽  
Water Activity ◽  
Rice Flour ◽  
Milling Process ◽  
Adsorption Properties ◽  
Water Molecules ◽  
Rice Flours ◽  
Changes Of State

ABSTRACT This study evaluated the influence of the milling process on solid state of rice flours according to water activity using ATR-FTIR. A band at 1740 cm−1 attributed to the C=O stretching of lipids was detected for crystalline samples, and it disappeared at a high aw range. The CH band at 2930 cm−1 of crystalline samples gradually shifted to a higher wavenumber with aw. This band of the α-formed and wet-milled samples shifted to higher wavenumbers above 0.8aw. A band due to OH stretching mode in the 3500-3000 cm−1 region did not shift with aw. The result obtained from IR spectra suggests that the parameter K calculated by Guggenheim–Anderson–de Boar model reflected not only the interaction between water molecules but also the changes of state in solids. Consequently, the results from this study provide insights about the adsorption properties of nonideal solids such as rice flour.

scholarly journals N,N-Dimethyl-2-[(1E)-({[(methylsulfanyl)methanethioyl]amino}imino)methyl]aniline

IUCrData ◽  
2018 ◽  
Vol 3 (3) ◽  
Author(s):  
Winaki P. Sohtun ◽  
Arunachalam Kannan ◽  
Saravanan Dhandayutham ◽  
Marappan Velusamy
Keyword(s):  
Solid State ◽  
Hydrogen Bonds ◽  
Benzene Ring ◽  
Title Compound ◽  
Tautomeric Form ◽  
Compound C

In the title compound, C11H15N3S2, the dithiocarbazate moiety is rotated by 18.73 (8)° with respect to the benzene ring. The dithiocarbazate group adopts anEconfiguration with respect to the C=N bond of the benzylidene group. Furthermore, in the solid state the compound exists in the thione tautomeric form. In the crystal, molecules are linked by pairs of weak N—H...S hydrogen bonds, forming inversion dimers which are arranged in layers parallel to (010).

3-(Pyridin-4-yl)acetylacetone: CdII and HgII compete for nitrogen coordination

2017 ◽  
Vol 73 (9) ◽  
pp. 724-730 ◽  
Author(s):  
Khai-Nghi Truong ◽  
Carina Merkens ◽  
Ulli Englert
Keyword(s):  
Solid State ◽  
Hydrogen Bonds ◽  
Carbonyl Group ◽  
Coordination Sphere ◽  
Aqua Ligand ◽  
Polymeric Chain ◽  
One Dimensional ◽  
Distorted Octahedral Coordination ◽  
Distorted Octahedral ◽  
The One

3-(Pyridin-4-yl)acetylacetone (HacacPy) acts as a pyridine-type ligand towards CdII and HgII halides. With CdBr2, the one-dimensional polymer [Cd(μ-Br)2(HacacPy)Cd(μ-Br)2(HacacPy)2]∞ is obtained in which five- and six-coordinated CdII cations alternate in the chain direction. Reaction of HacacPy with HgBr2 results in [Hg(μ-Br)Br(HacacPy)]∞, a polymer in which each HgII centre is tetracoordinated. In both compounds, each metal(II) cation is N-coordinated by at least one HacacPy ligand. Equimolar reaction between these CdII and HgII derivatives, either conducted in ethanol as solvent or via grinding in the solid state, leads to ligand redistribution and the formation of the well-ordered bimetallic polymer catena-poly[[bromidomercury(II)]-μ-bromido-[aquabis[4-hydroxy-3-(pyridin-4-yl)pent-3-en-2-one]cadmium(II)]-di-μ-bromido], [CdHgBr4(C10H11NO2)2(H2O)] n or [{HgBr}(μ-Br){(HacacPy)2Cd(H2O)}(μ-Br)2]∞. HgII and CdII cations alternate in the [100] direction. The HacacPy ligands do not bind to the HgII cations, which are tetracoordinated by three bridging and one terminal bromide ligand. The CdII centres adopt an only slightly distorted octahedral coordination. Three bromide ligands link them in a (2 + 1) pattern to neighbouring HgII atoms; two HacacPy ligands in a cis configuration, acting as N-atom donors, and a terminal aqua ligand complete the coordination sphere. Classical O—H...Br hydrogen bonds stabilize the polymeric chain. O—H...O hydrogen bonds between aqua H atoms and the uncoordinated carbonyl group of an HacacPy ligand in a neighbouring strand in the c direction link the chains into layers in the (010) plane.

scholarly journals Chaetomadrasins A and B, Two New Cytotoxic Cytochalasans from Desert Soil-Derived Fungus Chaetomium madrasense 375

Molecules ◽  
2019 ◽  
Vol 24 (18) ◽  
pp. 3240 ◽  
Author(s):  
Guo ◽  
Yin ◽  
Zhang ◽  
Kang ◽  
Wang ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Solid State ◽  
Carbonyl Group ◽  
Carcinoma Cells ◽  
Desert Soil ◽  
Indole Ring ◽  
Ring Compounds ◽  
Spectroscopic Analyses ◽  
First Time ◽  
Human Hepatocellular Carcinoma Cells

Two new cytochalasans, Chaetomadrasins A (1) and B (2), along with six known analogues (3–8), were isolated from the solid-state fermented culture of desert soil-derived Chaetomium madrasense 375. Their structures were clarified by comprehensive spectroscopic analyses, and the absolute configurations of Compounds 1 and 2 were confirmed by electronic circular dichroism (ECD) and calculated ECD. For the first time, Chaetomadrasins A (1), which belongs to the chaetoglobosin family, is characterized by the presence of all oxygen atoms in the form of Carbonyl. Chaetomadrasin B (2) represents the first example of chaetoglobosin type cytochalasan characterized by a hydroxy unit and carbonyl group fused to the indole ring. Compounds 1 and 2 displayed moderate cytotoxicity against HepG2 human hepatocellular carcinoma cells.

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