Abstract

Tms Outperforms Residual Chcl3 as an Internal Reference for Routine 1h Nmr Spectra Taken In Cdcl3

Author(s): Kirstein James

Over 60 years ago, tetramethylsilane was recommended for use as an internal reference chemical in proton NMR spectroscopy. Researchers frequently compare the chemical shifts of analytes to the remaining proton resonance in the deuterated solvent in which the spectrum is captured. The effect of various functional groups on the CHCl3 resonance is relevant since CDCl3 is the most often utilised NMR solvent for routine analysis of organic molecules. The results presented here illustrate why reference spectra to TMS rather than CHCl3 in CDCl3 produces more accurate chemical shifts and should be the preferred method. The use of a concentric tube configuration to measure distinct compartments of unperturbed CDCl3/TMS vs. CDCl3/TMS/solute solutions was crucial. This study is being presented in this forum since the audience/readership is appropriate and, hopefully, both responsive and grateful of the advice given.