scholarly journals Studies on the metabolism of unsaturated fatty acids. III. Structural determination of cis- and trans-isomers of 3- or 2-alkenoic acids by nuclear magnetic resonance spectroscopy using a chemical shift reagent.

1980 ◽  
Vol 28 (8) ◽  
pp. 2347-2350 ◽  
Author(s):  
MICHINAO MIZUGAKI ◽  
TOSHIAKI HOSHINO ◽  
YOKO ITO ◽  
TAKAO SAKAMOTO ◽  
TAKAYUKI SHIRAISHI ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Nuclear Magnetic Resonance ◽  
Unsaturated Fatty Acids ◽  
Shift Reagent ◽  
Resonance Spectroscopy ◽  
Structural Determination ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans

Comparison of Two Infrared Methods for the Determination of Isolated Trans Unsaturation in Fats, Oils, and Methyl Ester Derivatives

1971 ◽  
Vol 54 (6) ◽  
pp. 1288-1292
Author(s):  
Anita Huang ◽  
David Firestone
Keyword(s):  
Fatty Acids ◽  
Methyl Ester ◽  
Rapid Method ◽  
Unsaturated Fatty Acids ◽  
Methyl Esters ◽  
Tentative Method ◽  
Trans Isomers ◽  
Sample Matrix ◽  
Infrared Methods

Abstract A study was made to compare the rapid method reported by Allen with the tentative method of the American Oil Chemists’ Society for the determination of isolated (unconjugated) trans isomers of unsaturated fatty acids. The rapid method was found to be less accurate. The accuracy of the rapid method can be improved by using an oil or methyl ester matrix with the same composition as the sample matrix for the determination of K-and f-values used for calculation of per cent trans isomers. Results obtained with both methods for methyl esters were more accurate than results for vegetable oils. An analysis of variance was performed to compare the methods.

Reactivities of Piperazine-2,5-diones in Radical Bromination Reactions

1996 ◽  
Vol 49 (11) ◽  
pp. 1229 ◽  
Author(s):  
CLL Chai ◽  
DCR Hockless ◽  
AR King
Keyword(s):  
Crystal Structure ◽  
Amino Acid ◽  
Chemical Reactivity ◽  
Trans Isomers ◽  
Radical Bromination ◽  
Conformational Effects ◽  
Cis And Trans Isomers ◽  
The Difference ◽  
Cis And Trans

The reactivities of various N,N'- diacetylated piperazine-2,5-diones towards radical bromination reactions are reported. The studies show that glycyl centres of piperazine-2,5-diones are more reactive towards radical bromination reactions compared to α-substituted amino acid centres. In addition, large differences in reactivities were observed for the cis and trans isomers of N,N'-diacetylated alanine anhydride. Single-crystal structure determination of each isomer revealed that conformational effects may account for the difference in chemical reactivity.

Quantitative Determination and Confirmation of Low Levels of Diethylstilbestrol in Feeds

1972 ◽  
Vol 55 (6) ◽  
pp. 1345-1353
Author(s):  
Marshall T Jeffus ◽  
Charles T Kenner
Keyword(s):  
Thin Layer ◽  
Quantitative Determination ◽  
Official Method ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Before And After ◽  
Chromatographic Procedure ◽  
Low Levels ◽  
Cis And Trans

Abstract A method for the determination of diethylstibestrol in feeds, which is based on official first action method 38.048–38.051, is proposed. Interfering feed extractives are removed by using a tripotassium phosphate-Celite column prior to measurement at 415 nm before and after irradiation. Recoveries of equilibrated standards added to Soxhlet extracts of several samples averaged 94.3% compared to 86.3% by the official method. The background absorbance at 415 nm obtained by using the proposed method was approximately 6% of the background by the official method for solutions containing equivalent amounts of sample. A thin layer chromatographic method is also included for the confirmation and identification of the cis and trans isomers of the drug. The proposed method has been found satisfactory for the quantitative determination of 0.55–44 ppm diethylstilbestrol and the thin layer chromatographic procedure can detect as little as 0.07 ppm.

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