Tritium NMR?! What’s that look like?

Hello fellow NMR enthusiasts, have you ever wondered what tritium (³H) looks like via NMR? I know I have, and today, I would like to share some data with you.

Tritium, like deuterium, is an isotope of hydrogen. All three nuclei contain a single proton and electron but with varying amounts of neutrons: hydrogen having zero, deuterium having one, and tritium having two. Since chemistry revolves around the interactions between protons and electrons, it is not surprising that these isotopes have nearly the same chemical properties. Although they are similar, tritium is the only nucleus that is more sensitive than hydrogen in NMR.¹ Tritium would be the perfect nucleus to use for NMR except for two problems:

1. Tritium has an extremely low natural abundance, we are talking around 0.0000000000000003%¹

2. Tritium is radioactive, making it difficult to work with, so health and safety precautions must be considered before handling these samples

The main uses of tritium in everyday life are for self-powered lighting (radioluminescence). This is often used in firearm sights, watches, exits signs, as well as a variety of other devices. Tritium also has uses in analytical chemistry (radiolabelling), can be a source of electrical power (beta-voltaic devices), and can be an essential part of nuclear weapons, where it is used to enhance the efficiency and yield of fission bombs.²

Recently, we have been approached by Isotopes Canada to see if we could help them with the structural elucidation of one of their tritiated complexes. Usually, we would not be able to handle such compounds, but thankfully we had the experts at Isotopes Canada helping us with sample handling and preparation!

Figure 1. ¹H (60 MHz) NMR of propoxybenzene-t₁.

Figure 2.³H (64 MHz) NMR of propoxybenzene-t₁.

As expected, the ¹H NMR spectrum (Figure 1) shows 5 different signals with complex splitting patterns due to coupling between adjacent protons, as well as additional coupling between tritium and the aromatic resonances. The ³H NMR spectrum of propoxybenzene-t₁ show a triplet at ~8 ppm (Figure 2), which is expected of an aromatic signal coupling to 2 adjacent protons. If you have any questions about tritium NMR or any other features of our benchtop NMR, please don’t hesitate to reach out to us!

References

(1) Hydrogen (proton, deuterium, and tritium) NMR (http://chem.ch.huji.ac.il/nmr/techniques/1d/row1/h.html#BM2D) (accessed July 16, 2021)

(2) Tritium (https://en.wikipedia.org/wiki/Tritium) (accessed July 16, 2021)