A new series of mono- and dipiperidine, oxazoline, and oxazolidine crown ethers. Stability constants, ion transport rates, and nuclear magnetic resonance studies

1987 ◽  
Vol 65 (7) ◽  
pp. 1513-1520 ◽  
Author(s):  
J. Desroches ◽  
H. Dugas ◽  
M. Bouchard ◽  
T. M. Fyles ◽  
G. D. Robertson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Ion Transport ◽  
Crown Ethers ◽  
Chemical Shifts ◽  
Water Solution ◽  
Ion Pair ◽  
Resonance Spectroscopy ◽  
Carboxylate Groups ◽  
Nuclear Magnetic

A series of monopiperidine, 1, dipiperidine 2, 3 (syn and and), as well as the corresponding oxazoline and oxazolidine crown ethers have been prepared and their ionophoric properties evaluated. The syn-dipiperidine 2c turned out to be a particularly efficient Ca2+ ligand (log K = 9.7). 13C and 23Na nuclear magnetic resonance spectroscopy was used to evaluate the nature of the complex between the monopiperidine 1c, the syn-dipiperidine 2c, and Ca2+ and Na+ ions. In methanol–water solution, the dimeric salt (2c)2Ca exhibits both a tight or asymmetric and a symmetric or loose ion pair between the cation and the carboxylate groups. Sodium-23 chemical shifts and line-width variation both support a 1:1 complex with 1c and 2c. The structural results correlate with observations from ion transport experiments.

Metal – Aminopolycarboxylic Acid Complexes. III. Studies of Lead(II) – Tetraethylenepentaamineheptaacetic Acid in Aqueous Solution by Proton Nuclear Magnetic Resonance Spectroscopy

1971 ◽  
Vol 49 (12) ◽  
pp. 2096-2102 ◽  
Author(s):  
Peter Letkeman ◽  
Donald T. Sawyer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Electrostatic Interactions ◽  
Chemical Shifts ◽  
Ph Dependence ◽  
Proton Nuclear Magnetic Resonance ◽  
Resonance Spectroscopy ◽  
Carboxylate Groups ◽  
Nitrogen Bonds ◽  
Nuclear Magnetic

Proton nuclear magnetic resonance (n.m.r.) spectroscopy and the pH dependence of the chemical shifts of the nonlabile protons have been used to determine the preferred protonation sites in tetraethylenepentaamineheptaacetic acid (TPHA). The nitrogen atoms are protonated more readily than the carboxylate groups with the sequence of protonation dependent on electrostatic interactions. The 1:1 Pb(II)–TPHA complex which is not protonated for solution conditions from pH 10 to 14, has five metal–nitrogen bonds. The coordinate bonds are labile so that rapid interconversion between nonequivalent configurations produces an average configuration in which the protons of the acetate groups exhibit single n.m.r. peaks. Protonation of the complex probably occurs in three stages. From pH 10 to pH 8 the preferred protonation sites are the terminal nitrogen atoms with the attendant elimination of the metal–nitrogen bonds. Increasing the acidity to pH 4 causes all but the central nitrogen site to be protonated. Below pH 4 the central nitrogen atom becomes protonated and causes further unwrapping of the complex.

Studies of specifically fluorinated carbohydrates. Part II. Nuclear magnetic resonance studies of pentopyranosyl fluoride derivatives

1969 ◽  
Vol 47 (1) ◽  
pp. 19-30 ◽  
Author(s):  
L. D. Hall ◽  
J. F. Manville
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
Magnetic Resonance Studies ◽  
Conformational Model ◽  
Nuclear Magnetic

Detailed studies, by 1H and 19F nuclear magnetic resonance spectroscopy, of a series of fully esterified pentopyranosyl fluorides, show that all such derivatives favor that conformer in which the fluorine substituent is axially oriented. This conclusion is supported by separate considerations of the vicinal and geminal19F–1H and 1H–1H coupling constants, of the long-range (4J) 1H–1H and 19F–1H coupling constants and of the 19F chemical shifts. The limitations of the above conformational model are discussed.

scholarly journals Study of the biologically active acyclic ureas by nuclear magnetic resonance

2020 ◽  
Vol 100 (4) ◽  
pp. 60-74
Author(s):  
А.А. Bakibaev ◽  
◽  
М.Zh. Sadvakassova ◽  
V.S. Malkov ◽  
R.Sh. Еrkasov ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Functional Groups ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Biologically Active ◽  
Resonance Spectroscopy ◽  
13C Nmr Spectra ◽  
Nuclear Magnetic

A wide variety of acyclic ureas comprising alkyl, arylalkyl, acyl, and aryl functional groups are investigated by nuclear magnetic resonance spectroscopy. In general, spectral characteristics of more than 130 substances based on acyclic ureas dissolved in deuterated dimethyl sulfoxide at room temperature are studied. The re-sults obtained based on the studies of 1H and 13C NMR spectra of urea and its N-alkyl-, N-arylalkyl-, N-aryl- and 1,3-diaryl derivatives are presented, and the effect of these functional groups on the chemical shifts in carbonyl and amide moieties in acyclic urea derivatives is discussed. An introduction of any type of substitu-ent (electron-withdrawing or electron-donating) into urea molecule is stated to result in a strong upfield shift in 13C NMR spectra relatively to unsubstituted urea. A strong sensitivity of NH protons to the presence of acyl and aryl groups in nuclear magnetic resonance spectra is pointed out. In some cases, qualitative depend-encies between the chemical shifts in the NMR spectra and the structure of the studied acyclic ureas are re-vealed. A summary of the results on chemical shifts in the NMR spectra of the investigated substances allows determining the ranges of chemical shift variations of the key protons and carbon atoms in acyclic ureas. The literature describing the synthesis procedures are provided. The results obtained significantly expand the methods of reliable identification of biologically active acyclic ureas and their metabolites that makes it promising to use NMR spectroscopy both in biochemistry and in clinical practice.

Sign in / Sign up

Export Citation Format

Share Document