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Gift A.D., Stewart S.M., and Bokashanga K.P., Experimental Determination of pKa Values by use of NMR Chemical Shifts, Revisited”, J. Chem. Educ. 89, 1458 – 1460, August 2012

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Article

Application of 1H-NMR for the Quantitative Analysis of Short Chain Fatty Acid Methyl Ester Mixtures: An Undergraduate Instrumental Analysis Experiment

1Department of Chemistry, Hofstra University, Hempstead, N.Y., USA


World Journal of Chemical Education. 2015, Vol. 3 No. 2, 46-50
DOI: 10.12691/wjce-3-2-4
Copyright © 2015 Science and Education Publishing

Cite this paper:
Ronald. P. D’Amelia, Ling Huang, William F. Nirode, Eve Rotman, Jayni Shumila, Nanette M. Wachter. Application of 1H-NMR for the Quantitative Analysis of Short Chain Fatty Acid Methyl Ester Mixtures: An Undergraduate Instrumental Analysis Experiment. World Journal of Chemical Education. 2015; 3(2):46-50. doi: 10.12691/wjce-3-2-4.

Correspondence to: Ronald.  P. D’Amelia, Department of Chemistry, Hofstra University, Hempstead, N.Y., USA. Email: Ronald..p.damelia@hofstra.edu

Abstract

Nuclear magnetic resonance spectroscopy (NMR) is one of the most important instrumental techniques used to elucidate the molecular structure of organic compounds. However, there are not many good simple applications of using NMR for the quantitative assay of impure or mixtures of organic substances. The current experiment was developed as part of an ongoing effort to increase exposure to quantitative proton NMR methodology in the undergraduate chemistry laboratory curriculum. The objective of the experiment is to determine the percent composition of a two component mixture of short chain fatty acid methyl esters using chemical shift and integration values obtained from running solvent-less samples both with and without an internal reference standard. We report on the experimental methods and results obtained from examining the quantitative NMR properties of a series of mixtures of methyl acetate (M.A.) and methyl propionate (M.P.) solutions ranging from 100% MA to 100% MP. Also similar data was obtained for the MA - methyl butyrate (MB) pair. The results exhibit a linear relationship of the percent composition of the methyl acetate binary mixtures found by proton NMR with the theoretical (i.e. samples prepared based on measured weights) percent compositions. The experiment confirms the quantitative usage of 1H NMR and serves as an educational tool for the undergraduate chemical laboratory.

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