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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Yes—but only for one specially engineered carbene under the conditions tested. A 2025 study reports that a chlorinated, carborane-shielded N-heterocyclic carbene was generated in water and showed no decomposition during six months of NMR monitoring in a water-saturated, single-phase tetrahydrofuran (THF) solution. That is evidence for this protected molecule, not a general property of carbenes.
What the 2025 study found
In “Confirmation of Breslow’s hypothesis: A carbene stable in liquid water,” published in Science Advances on April 11, 2025, the authors describe synthesizing and characterizing a persistent carbene. They used nuclear magnetic resonance (NMR) and single-crystal X-ray diffraction to characterize the compound, and report generating it in water. The paper is available from Science Advances; its publication record is also listed by PubMed.
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The persistence result has a specific experimental setting: the sample was in water-saturated THF, which formed a single-phase solution. The authors report that NMR monitoring over six months showed no decomposition. This is not a claim that an unprotected carbene can be left in ordinary bulk water indefinitely.
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A carbene has a divalent carbon center that is typically highly reactive. In this molecule, the N-heterocyclic carbene core has nitrogen substituents carrying chlorinated 10-vertex carborane clusters. The researchers’ design rationale is that the bulky clusters physically shield the reactive center, while chlorination helps favor carbene formation by drawing electron density away from the divalent carbon. These features explain the design of this compound; they do not establish that other carbenes will resist water in the same way.
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What this means for Breslow’s hypothesis
In 1958, Ronald Breslow proposed that thiamine (vitamin B1) could generate a transient N-heterocyclic carbene involved in biochemical catalysis. The 2025 result shows that a suitably protected carbene can be generated and persist in an aqueous environment, giving direct evidence for that possibility under carefully engineered conditions.
It does not recreate vitamin B1 catalysis or show that a carbene in an enzyme is stable in bulk water. The study’s authors say their carborane scaffold does not exactly mimic the active site of the enzymes Breslow considered. Chemistry World’s coverage quotes University of Cologne carbene specialist Albrecht Berkessel emphasizing that Breslow’s hypothesis does not require a carbene stable in liquid water. The biological comparison is therefore suggestive context, not proof about an enzyme mechanism.
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Why the result is narrower than “carbenes are stable in water”
- One designed molecule: The result concerns a particular carborane-shielded N-heterocyclic carbene, not carbenes as a class.
- A defined environment: The six-month observation was made in water-saturated, single-phase THF, not an unspecified aqueous setting.
- Persistence is not catalytic usefulness: The compound is described as exceptionally unreactive. The result does not show it is a more useful catalyst than earlier water-resistant carbenes.
- Biological relevance has limits: The experiment supports the possibility of persistence in a protected model system, but does not establish the stability of biological carbene intermediates.
So the precise conclusion is that one deliberately shielded carbene remained intact under the study’s aqueous conditions. Whether other structures can do so, or whether this particular molecule is useful in catalysis, is a separate question.
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