Application of Quantitative Proton Nuclear Magnetic Resonance Spectroscopy for the Compositional Analysis of Short Chain Fatty Acid Benzyl Ester Mixtures

Abstract

Nuclear Magnetic Resonance (NMR) has become one of the cornerstones of instrumental analysis work done in chemistry laboratories. NMR is most powerful when used quantitatively, the technique of using NMR to quantify the concentration of an analyte is referred to as qNMR and proton NMR, in particular, is extremely useful in this pursuit to quantify organic compounds. In order to increase exposure to the quantitative and qualitative aspects of NMR in the undergraduate chemistry laboratory, we have created a qNMR experiment to be used in analytical chemistry and instrumental analysis courses. The objective of the experiment was to determine the % composition of a two-component mixture of benzyl acetate (BA), benzyl propionate (BP), and benzyl butyrate (BB). We report on the methodologies used to determine % BA, BP, and BB. Mixtures ranged from 100% to 20%. The results show a strong linear relationship relating known weight %’s with qNMR weight %’s and serves as confirmation of the quantitative utility of proton NMR as well as an educational tool for the undergraduate chemical laboratory.