Echange isotopique hydrogène–deutérium subi par les groupements méthyles de la triméthyl-4,5,6 pyrimidone-2

1981 ◽  
Vol 59 (8) ◽  
pp. 1270-1276 ◽  
Author(s):  
Eric Picquenard ◽  
Pierre Dizabo
Keyword(s):  
Exchange Rate ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Neutral Molecule ◽  
Resonance Spectroscopy ◽  
Methyl Groups ◽  
Exchange Study ◽  
Conjugate Acid

The rate of deuterium exchange of 4 and 6 methyl protons in 4,5,6-trimethyl-2-pyrimidone has been followed in D2O over a range of acidity from pD 0.4 to 7.7 by means of proton magnetic resonance spectroscopy. The maximum of exchange rate represents equimolar proportions of the pyrimidone and its conjugate acid. The maximum is due to the neutral molecule acting as a base and removing a proton from one of the methyl groups of its conjugate acid. The exchange study of methyl protons in 1,4,5,6-tetramethyl-2-pyrimidone corroborates this mechanism.

General-base-catalyzed Proton Exchange in Glycocyamidiniom Ions: A Comparison of Activation by Protonation and by Alkylation

1975 ◽  
Vol 53 (19) ◽  
pp. 2906-2910 ◽  
Author(s):  
Ross Stewart ◽  
R. Srinivasan
Keyword(s):  
Exchange Rate ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Proton Exchange ◽  
Resonance Spectroscopy ◽  
Methyl Groups ◽  
General Base ◽  
Satisfactory Model ◽  
Conjugate Acid

The rates of exchange of methylene protons in seven glycocyamidinium ions in formate and chloroacetate buffers were measured in D2O by means of proton magnetic resonance spectroscopy. When protonation and methylation of glycocyamidines occur at the same site the methyated products react faster than the protonated products by factors of 1.8–1.9. Replacing ring protons in glycocyamidinium ions by methyl groups causes small increases in the méthylène exchange rate whereas corresponding substitution at the exocyclic nitrogen causes small rate decreases. It is concluded that in this reaction a quaternary ion ZR+ can serve as a satisfactory model for the analogous conjugate acid ZH+.

Trimethylaluminium: Scrambling of methyl groups in the dimer and exchange with trimethylgallium

1969 ◽  
Vol 22 (6) ◽  
pp. 1129 ◽  
Author(s):  
EA Jeffery ◽  
T Mole
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Methyl Groups ◽  
Cage Effect ◽  
Rate Determining Step

Interchange of methyl groups between the bridging and terminal positions of trimethylaluminium dimer and exchange of methyl groups between trimethyl- aluminium and trimethylgallium in cyclopentane have been re-examined, again by means of proton magnetic resonance spectroscopy. Dissociation of the dimer is confirmed as the rate- determining step in both cases, but the rate of dissociation is much greater in toluene than in cyclopentane. The evidence previously put forward for a cage effect limiting the rate of exchange with trimethylgallium in cyclopentane is refuted and a revised mechanism for exchange is suggested.

scholarly journals Imaging intelligence with proton magnetic resonance spectroscopy

Intelligence ◽  
2009 ◽  
Vol 37 (2) ◽  
pp. 192-198 ◽  
Author(s):  
Rex E. Jung ◽  
Charles Gasparovic ◽  
Robert S. Chavez ◽  
Arvind Caprihan ◽  
Ranee Barrow ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy

Disulfiram Determination by Proton Magnetic Resonance Spectroscopy and by Colorimetry

1973 ◽  
Vol 56 (1) ◽  
pp. 124-127 ◽  
Author(s):  
Eric B Sheinin ◽  
Walter R Benson ◽  
Myron M Smith
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Colorimetric Method ◽  
Drug Substance ◽  
Resonance Spectroscopy ◽  
Pmr Spectroscopy ◽  
Label Claim ◽  
Tablet Excipients

Abstract Disulfiram was determined in disulfiram drug substance and tablets by proton magnetic resonance (PMR) spectroscopy at the 100–480 mg level and by a colorimetric technique involving cuprous iodide at the 50 mg level. The tablet excipients do not interfere in the analysis. The average result for disulfiram in a tablet composite was 100.8±1.4% of label claim by PMR and 100.7±0.4% by the colorimetric method.

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