The Trifluoroacetic Acid Solvent System. Part II. Acids

1971 ◽  
Vol 49 (18) ◽  
pp. 2937-2942 ◽  
Author(s):  
M. G. Harriss ◽  
J.B Milne
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Trifluoroacetic Acid ◽  
Solvent System ◽  
Fluoroacetic Acid ◽  
Mixed Anhydrides ◽  
System Part ◽  
Nuclear Magnetic

19F nuclear magnetic resonance (n.m.r.) studies show that SbF5 forms HSbF5(OOCCF3) in tri-fluoroacetic acid. This complex acid does not react with (CF3CO)2O which must be added to carry out conductimetric studies in anhydrous HOOCCF3. However, HClO4, HSO3F, and HNO3 all react with (CF3CO)2O to yield mixed anhydrides CF3COClO4, CF3COSO3F, and NO2OOCCF3. HBF4 reacts with the anhydride to give CF3COF while H2SO4 appears to be simply dehydrated to polysulfuric acids.

Nuclear Magnetic Resonance Analysis of Pharmaceuticals. IX. Methenamine and Methenamine Mandelate in Tablets

1973 ◽  
Vol 56 (3) ◽  
pp. 669-673
Author(s):  
John W Turczan ◽  
Bruce A Goldwitz
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Maleic Acid ◽  
Mandelic Acid ◽  
Internal Standard ◽  
Solvent System ◽  
Nuclear Magnetic Resonance Analysis ◽  
Resonance Analysis ◽  
Nuclear Magnetic

Abstract An NMR procedure is described by which methenamine and mandelic acid are simultaneously determined in methenamine and methenamine mandelate tablets. Maleic acid was chosen as the internal standard and dimethylformamide-acetone-acetonitrile (10+25+65) as the solvent. The solvent system was selected to resolve the problems of solubility of methenamine and its salt with mandelic acid, overlapping of the resonance signals of the components, and potential decomposition of methenamine. Known standard and commercial preparations were analyzed and the results were compared to those of official USP and NF procedures. The NMR technique, when applied to the determination of methenamine and methenamine mandelate in tablets, is rapid, simple, and specific and can provide an assay with an accuracy of 1–2%.

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