THE DECOMPOSITION OF 2-METHYL-Δ2-OXAZOLINE IN AQUEOUS SOLUTION

1963 ◽  
Vol 41 (7) ◽  
pp. 1662-1670 ◽  
Author(s):  
R. Greenhalgh ◽  
R. M. Heggie ◽  
M. A. Weinberger
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Water Concentration ◽  
Acidity Function ◽  
First Order ◽  
Ph Values ◽  
Constant Ph ◽  
Kinetic Expression ◽  
Ph Range

Nuclear magnetic resonance has been used to follow the decomposition of aqueous solutions of 2-methyl-Δ2-oxazoline (0.29 M) at constant pH values in the range −1 to 14. The decomposition is first order with respect to total oxazoline at any specific pH, but deviates from the simple reaction of water with the protonated species above pH 5. At neutral pH values this is shown to be partially due to a second reaction involving 2-methyl-Δ2-oxazoline and O-acetylethanolamine which yields N-2-acetoxyethyl N′-2-hydroxyethyl acetamidate. The decrease in rate constant at pH < 2 is accounted for by variation in the water concentration, which is related to the acidity function. A kinetic expression is derived for the decomposition over the whole pH range studied. The decomposition of the amidate is also discussed.

Complexes of tungsten(VI) with thiomalic acid studied by 1H and 13C nuclear magnetic resonance spectroscopy

1984 ◽  
Vol 62 (11) ◽  
pp. 2094-2100 ◽  
Author(s):  
M. Madalena Caldeira ◽  
Victor M. S. Gil
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Sodium Tungstate ◽  
Stable Complex ◽  
Resonance Spectroscopy ◽  
Ph Values ◽  
13C Nuclear Magnetic Resonance ◽  
Metal Ligand

Proton and carbon-13 nmr evidence is presented on the number, stoichiometry, geometry, and stability of the complexes which form when sodium tungstate and (D,L)-thiomalic acid are mixed in aqueous solution at pH values in the range 2–7. In particular, three (or four) complexes are detected having a 1:2 composition (metal–ligand), as well as a less stable complex which seems to be a 1:1 species. Preliminary data are also given on the exchange of bound ligand in these complexes.

Quantitative Determination of Sodium Dodecatungstosilicate Speciation by 183W Nuclear Magnetic Resonance Spectroscopy

2002 ◽  
Vol 55 (4) ◽  
pp. 281 ◽  
Author(s):  
B. J. Smith ◽  
V. A. Patrick
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
High Concentration ◽  
Ph Range ◽  
Nuclear Magnetic

The speciation and equilibria of sodium dodecatungstosilicate has been determined using 183W nuclear magnetic resonance (NMR) spectroscopy over the pH range 3-13.5. The use of NMR allowed the direct observation of polytungstate anions in aqueous solution and at high concentration (0.5 mol L-1). Using this technique, the speciation of α-[SiW12O40]4-, α-[SiW11O39]8-, α-[NaSiW11O39]7-, α-[H2W12O40]6-, [H8W11O40]6-, [H7W11O40]7-, [W7O24]6-, [H2W12O42]10-, and WO42- was quantified as a function of pH. This work has allowed stability constants for α-[SiW12O40]4- (log K 46) and α-[SiW11O39]8- (log K 86) to be estimated.

Etude conformationnelle par résonance magnétique nucléaire du carbone 13 de peptides à activité antalgique

1980 ◽  
Vol 58 (11) ◽  
pp. 1241-1246 ◽  
Author(s):  
Robert René Smolders ◽  
Roland Coomans ◽  
Françoise Jacquemotte ◽  
Yves Van Haverbeke ◽  
André Maquestiau ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Trans Conformation ◽  
Magnetic Resonance Studies ◽  
Ph Values ◽  
Résonance Magnétique ◽  
Nuclear Magnetic

13C Nuclear magnetic resonance studies of proline peptides with central antalgic activity (Pro-Arg, Arg-Pro, Pro-Arg-Pro, Pro-Lys-Pro) indicate a predominance of trans conformation at all pH values; but their physiological activities appear to be related to the ability of the C-terminal proline peptides to assume the cis conformation.

Sign in / Sign up

Export Citation Format

Share Document