Is an Extremely Low-Field Proton Signal in the NMR Spectrum Conclusive Evidence for a Low-Barrier Hydrogen Bond?

1997 ◽  
Vol 101 (46) ◽  
pp. 8727-8733 ◽  
Author(s):  
Mireia Garcia-Viloca ◽  
Ricard Gelabert ◽  
Angels González-Lafont ◽  
Miquel Moreno ◽  
José M. Lluch
Keyword(s):  
Hydrogen Bond ◽  
Conclusive Evidence ◽  
Nmr Spectrum ◽  
Low Field ◽  
Proton Signal

scholarly journals Beiträge zur Chemie des Phosphors, 204. Zur Existenz eines Triphosphacyclobutenid-Ions P3CH2Ɵ / Contributions to the Chemistry of Phosphorus, 204. On the Existence of a Triphosphacyclobutenide Ion P3CH2e

1990 ◽  
Vol 45 (8) ◽  
pp. 1139-1142 ◽  
Author(s):  
Marianne Baudler ◽  
Josef Hahn
Keyword(s):  
White Phosphorus ◽  
Complete Analysis ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Low Field

The structure of the reaction product of white phosphorus and sodium in diglyme which exhibits a low field AB2 system in the 31P{1H} NMR spectrum [4] has been reexamined. According to the results of a complete analysis of its proton coupled 31P NMR spectrum (ABB′XX′ system), the compound is the hitherto unknown 1,2,3-triphosphacyclopentadienide ion P3(CH)2⊖ (4), and not the triphosphacyclobutenide ion P3CH2⊖(3) previously assumed [4]. The parameters of the Ρ,Η-coupled 31P NMR spectrum of the tetraphosphacyclopentadienide ion P4CH⊖ (2) have also been calculated.

Coupling constants nitrogen-15-nitrogen-15 and nitrogen-15-hydrogen in phenylhydrazones forming hydrogen bond

1981 ◽  
Vol 46 (4) ◽  
pp. 892-897 ◽  
Author(s):  
Antonín Lyčka ◽  
Dobroslav Šnobl
Keyword(s):  
Hydrogen Bond ◽  
Carbonyl Group ◽  
Ester Group ◽  
Natural Abundance ◽  
Coupling Constants ◽  
The Other ◽  
A Value ◽  
Proton Signal ◽  
Hydrazone Form

Absolute values of the coupling constants 1J(15N15N), 1J(15NH) of six phenylhydrazones forming hydrogen bond, 2J(15N15NH) of four, and 4J(15NH) of two phenylhydrazones have been determined. Three coupling constants 1J(15N15N) have been obtained from the nitrogen-15 monolabelled compounds by measuring the other nitrogen at natural abundance. The coupling constants 2J(15N15NH) have been measured with the nitrogen-15 doubly labelled compounds, because in the arrangement 15N14NH there exists a broadening of the proton signal due to nitrogen-14. Absolute values of the coupling constants 1J(15N15N) of the phenylhydrazones forming hydrogen bond to the ester group are smaller ( 10.8 Hz) than those of the phenylhydrazones having hydrogen bond to carbonyl group ( 11.1 Hz). The coupling constants 2J(15N15NH) have a value 2.4 ± 0.2 Hz. The value of 1J(15N15N) of 1-phenylazo-2-naphthalenol decreases with increasing content of hydrazone form. The values of 2J(15N15NH) of this compound are within 1.2 to 1.6 Hz.

Water Molecular Motion and Hydrogen Bond in Paramagnetic [Cu(H2O)6][PtCl6] as Studied by Single Crystal 2H NMR

2000 ◽  
Vol 55 (1-2) ◽  
pp. 178-182 ◽  
Author(s):  
Motohiro Mizuno ◽  
Takahiro Iijima ◽  
Kengo Orii ◽  
Masahiko Suhara
Keyword(s):  
Activation Energy ◽  
Hydrogen Bond ◽  
Water Molecule ◽  
Single Crystal ◽  
Nmr Spectra ◽  
Molecular Motion ◽  
2H Nmr ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Infinite Temperature

The temperature and angular dependences of the 2H NMR spectrum were measured for single crystal [Cu(H2O)6][PtCl6]. (e2Qq/h, η) = (132 kHz, 0.72) were obtained for the D nucleus averaged by the fast 180° flip of the water molecule at 297 K. D1(236 kHz, 0.10) and D2(246 kHz, 0.09) were obtained for two unequal D nuclei of the water molecule at 133 K. Below Tc , at least three nonequivalent waters were found to exist. The jumping rate for the 180° flip of the water molecule (k) was obtained from the simulation of 2H NMR spectra at H0||[111] direction. The activation energy Ea and the jumping rate at infinite temperature were estimated from the temperature dependence of k to be 24kJmol-1 and 1 x 1013s-1

scholarly journals Synthesis, anticancer and FGFR1 inhibitory activity of isoindolo[2,1-a][1,2,4]triazino[2,3-c]quinazoline derivatives

2016 ◽  
Author(s):  
O. Yu. Voskoboynik ◽  
S. A. Starosyla ◽  
M. V. Protopopo ◽  
H. P. Volynets ◽  
S. V. Shyshkina ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Acetic Acid ◽  
Inhibitory Activity ◽  
Spectral Properties ◽  
Docking Study ◽  
Benzoic Acids ◽  
Low Field ◽  
Quinazoline Derivatives

Presented manuscript describes the synthesis, antitumor and FGFR1 inhibitory activity of novel isoindolo[2,1-a][1,2,4]triazino[2,3-c]quinazolines. It was shown that mentioned above substances may be prepared by interactionof 3-(2-amino-3-R2-5-R3-phenyl)-6-R1-1,2,4-triazin-5(2H)-ones with 2-formylbenzoic and 6-formyl-2,3-dimethoxybenzoic (opianic) acids in acetic acid. It was shown that proper 2-(2-oxo-3-R-6,7-dihydro-2H-[1,2,4]triazino[2,3-c]quinazolin-6-yl)benzoic acids (or corresponded dimethoxysubstituted analogues) may be considered as intermediates of thereaction. Spectral properties of synthesized compounds were studied, it was shown that protons in position 8 wereobserved at low field as result of the presence of hydrogen bond between hydrogen at position 8 and oxygen atposition 10. The anticancer assay data allowed to identify synthesized compounds as promising antitumor agents.The FGFR1 inhibitory activity of synthesized compounds was detected and docking study aimed to the evaluationof mentioned action was conducted.

NMR studies of 1-phenylazo-3-substituted-2-naphthols in solution and in the solid state

1990 ◽  
Vol 55 (1) ◽  
pp. 193-201 ◽  
Author(s):  
Antonín Lyčka ◽  
Miroslav Nečas ◽  
Josef Jirman ◽  
Jaroslav Straka ◽  
Bohdan Schneider
Keyword(s):  
Hydrogen Bond ◽  
Solid State ◽  
Nmr Spectra ◽  
Equilibrium Mixture ◽  
Mas Nmr ◽  
Nmr Studies ◽  
Nmr Spectrum ◽  
Cp Mas Nmr ◽  
Hydrazone Form

The 1H and 15Nα-enriched 1-phenylazo-3-X-2-naphthols, where X = COOH (I), X = COOCH3 (II), and X = CONHC6H5 (III), have been measured in various solvents. The values of 1J(15Nα, H) and σ(15N) indicate that in CDCl3, C6D6, CCl4, and CD3NO2 solutions the compounds I and III exist practically completely in their hydrazone forms. The hydrazone form is stabilized by the hydrogen bond of COOH or CONH protons to the C(2)=O group. The compound II represents an equilibrium mixture of azo and hydrazone forms, since it cannot form a similar hydrogen bond. Moreover, the 15N NMR spectra of compounds I-III have been measured in solid state by the CP/MAS technique. The results indicate the existence of two conformers differing by the conformation of COOCH3 group in compound II, which is supported by the 13C CP/MAS NMR spectrum of compound II.

Synthesis and intramolecular hydrogen bonding of syn-9-hydroxy-18-substituted [3.3]metacyclophanes

2012 ◽  
Vol 90 (2) ◽  
pp. 222-229 ◽  
Author(s):  
Kazuya Tazoe ◽  
Xing Feng ◽  
Bigyan Sharma ◽  
Shinpei Miyamoto ◽  
Takehiko Yamato
Keyword(s):  
Hydrogen Bonding ◽  
Coupling Reaction ◽  
Sodium Hydride ◽  
Intramolecular Hydrogen Bonding ◽  
Aromatic Rings ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Low Field ◽  
Field Shift ◽  
Intramolecular Hydrogen

Various anti-9-methoxy[3.3]metacyclophane-2,11-diones are exclusively obtained by the coupling reaction of the corresponding 1,3-bis(bromomethyl)benzenes and 2,6-bis[2-isocyano-2-(tolylsulfonyl)ethyl]-4-tert-butylanisole in dimethylformamide (DMF) with an excess of sodium hydride, from which the corresponding syn-[3.3]metacyclophanes (MCPs) are synthesized via anti/syn-isomerization during the Wolff–Kishner reduction. Demethylation of syn-9-methoxy[3.3]MCPs with BBr3 afforded the corresponding syn-9-hydroxy[3.3]MCPs in good yields. The existence of the strong intramolecular hydrogen bonding between the 9-hydroxy group and the 18-substituents, such as F, OH, and OMe groups at the opposing aromatic rings, are observed in solution and in the solid state. A distinct low-field shift of the phenolic OH proton was observed in the 1H NMR spectrum compared with that of the 18-unsubstituted analog. Furthermore, O–H···F through-space coupling was observed.

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