Heavy‐Atom Tunneling in Organic Reactions

Castro, Claire; Karney, William L.

doi:10.1002/anie.201914943

Cited by 69 publications

(82 citation statements)

References 62 publications

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“…Also, the matrix material might interact differently with various derivatives of the same compound class. A very recent study in the realm of heavy‐atom tunneling [72] addresses the interplay of these effects [73] . Disentangling the influences on tunneling half‐lives to draw a clearer picture how to effectively control QMT remains an ongoing endeavor.…”

Section: Resultsmentioning

confidence: 99%

Characterization of the Simplest Thiolimine: The Higher Energy Tautomer of Thioformamide

Bernhardt

Dressler

Eckhardt

et al. 2021

Chemistry A European J

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As sulfur‐containing organic molecules thioamides and their isomers are conceivable intermediates in prebiotic chemistry, for example, in the formation of amino acids and thiazoles and resemble viable candidates for detection in interstellar media. Here, we report the characterization of parent thioformamide in the solid state via single‐crystal X‐ray diffraction and its photochemical interconversion to its hitherto unreported higher energy tautomer thiolimine in inert argon and dinitrogen matrices. Upon photogeneration, four conformers of thiolimine form, whose ratio depends on the employed wavelength. One of these conformers interconverts due to quantum mechanical tunneling with a half‐life of 30–45 min in both matrix materials at 3 and 20 K. A spontaneous reverse reaction from thiolimine to thioformamide is not observed. To support our experimental findings, we explored the potential energy surface of the system at the AE‐CCSD(T)/aug‐cc‐pCVTZ level of theory and computed tunneling half‐lives with the CVT/SCT approach applying DFT methods.

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Section: Resultsmentioning

confidence: 99%

Characterization of the Simplest Thiolimine: The Higher Energy Tautomer of Thioformamide

Bernhardt

Dressler

Eckhardt

et al. 2021

Chemistry A European J

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“…QMT is a well-known effect for hydrogen-based reactions, but only recently it was established that "heavy" atom tunneling (i. e. second-row atoms) can also play an important role for reactions with low and, most importantly, narrow barriers. [31][32][33][34][35][36] The LB to SB reactions presented here indeed involve low barriers with relatively short trajectories. However, they also require the movement of heavy atoms, potentially hindering any realistic QMT mechanism.…”

Section: Introductionmentioning

confidence: 61%

Boron Tunneling in the “Weak” Bond‐Stretch Isomerization of N−B Lewis Adducts

et al. 2021

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Some nitrile-boron halide adducts exhibit a double-well potential energy surface with two distinct minima: a "long bond" geometry (LB, a van der Waals interaction mostly based on electrostatics, but including a residual charge transfer component) and a "short bond" structure (SB, a covalent dative bond). This behavior can be considered as a "weak" form of bond stretch isomerism. Our computations reveal that complexes RCNÀ BX 3 (R = CH 3 , FCH 2 , BrCH 2 , and X = Cl, Br) exhibit a fast interconversion from LB to SB geometries even close to the absolute zero thanks to a boron atom tunneling mechanism. The computed half-lives of the meta-stable LB compounds vary between minutes to nanoseconds at cryogenic conditions. Accordingly, we predict that the long bond structures are practically impossible to isolate or characterize, which agrees with previous matrix-isolation experiments.

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“…The study of the  bond-shifting of PL 57 was originally inspired by the grandparent of all heavy atom QT reactions: the automerization of cyclobutadiene. [45][46][47]82,83 It was clear that the reaction can proceed by an extremely fast tunnelling even close to the absolute zero, with a computed rate constant of 1.1×10 8 s -1 (see table 1). Since then, many other similar reactions were tested, most of them showing the same signs of QT.…”

Section: Pentalene (Pl)mentioning

confidence: 99%