Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Researchers observed two conformers of the same triplet nitrene rearranging at the same time into different products: one through heavy-atom tunnelling and the other through hydrogen-atom tunnelling. The experiment used a nitrogen matrix at 10 and 20 K, so it demonstrates an unusual form of reaction control in a highly specialized setting—not a ready-made method for ordinary synthesis.
What the researchers observed
The 2022 study examined triplet 2-formyl-3-fluorophenylnitrene, produced by ultraviolet irradiation of 2-formyl-3-fluorophenyl azide held in a nitrogen matrix. Infrared spectroscopy tracked the products and reaction kinetics at 10 and 20 K.
As an Amazon Associate I earn from qualifying purchases.
The starting nitrene existed in two conformers, called syn and anti. Rather than first interconverting, each followed a distinct rearrangement: the syn conformer formed 2,1-benzisoxazole, while the anti conformer formed imino-ketene. The authors assign the first pathway to heavy-atom tunnelling and the second to hydrogen-atom tunnelling.
How the two pathways compare
| Conformer | Assigned tunnelling pathway | Product | Reported rate and half-life |
|---|---|---|---|
| Syn | Heavy-atom tunnelling | 2,1-benzisoxazole | Approximately 1 × 10⁻³ s⁻¹; approximately 11 minutes |
| Anti | Hydrogen-atom tunnelling | Imino-ketene | Approximately 6 × 10⁻³ s⁻¹; approximately 2 minutes |
These approximate rate constants and half-lives are for the reported matrix-isolated system; they should not be treated as general rates for tunnelling reactions. The authors measured temperature-independent rates across the 10 K and 20 K conditions.
#1 Best Overall
Why tunnelling matters in this result
In a simplified classical picture, a reacting molecule crosses an energy barrier by acquiring enough energy to reach a transition state. Quantum tunnelling provides another route: particles can pass through a barrier even when they do not have the classical energy to cross over it. Hydrogen tunnelling is familiar in some chemical contexts because hydrogen is light. Tunnelling by heavier atoms is less common and can be especially sensitive to the system and barrier.
In this experiment, calculations supported the proposed pathways. The authors report that the conformers did not interconvert, even though their computed interconversion barrier was lower than the barriers associated with the observed rearrangements. Their interpretation is that neither conventional kinetic nor thermodynamic control accounts for the product outcome in this particular system; tunnelling control does.
Rank #2
What “simultaneous” means—and what it does not
“Simultaneous” describes concurrent reactions from two conformers present in the experimental system. It does not mean one molecule made both products at once: the syn conformer produced one product, and the anti conformer produced the other. Nor does the result establish that routine reactions generally proceed by tunnelling, or that the same chemistry occurs under everyday laboratory conditions.
Recommended Free Tools
The researchers discussed studying reactivity under conditions closer to conventional laboratory settings, including higher temperatures and liquid-phase conditions. Those are future directions, not results demonstrated by this experiment.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.The paper behind the discovery
The study, “Simultaneous Tunneling Control in Conformer-Specific Reactions,” was written by Cláudio M. Nunes, José P. L. Roque, Srinivas Doddipatla, Samuel A. Wood, Robert J. McMahon, and Rui Fausto. It appeared in Journal of the American Chemical Society, volume 144, issue 45, pages 20866–20874 (2022), and was published online November 2, 2022. Read the paper’s publication record and abstract.
In a November 24, 2022 report by Chemistry World, study leader Cláudio Nunes said the work “opens perspectives to look at reactivity a different way.”
Quick Recap
Rank #4
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →
