CONFORMER-SPECIFIC [1,2]H-TUNNELING IN CAPTODATIVELY-STABILIZED CYANOHYDROXYCARBENE (NC–C–OH)

Eckhardt, André K.

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https://hdl.handle.net/2142/107570 Copy

Description

Title

CONFORMER-SPECIFIC [1,2]H-TUNNELING IN CAPTODATIVELY-STABILIZED CYANOHYDROXYCARBENE (NC–C–OH)

Author(s)

Eckhardt, André K.

Contributor(s)

Schreiner, Peter R. ; Erb, Frederik R.

Issue Date

24-Jun-20

Keyword(s)

Conformers and isomers

Abstract

We report the gas-phase preparation of cyanohydroxycarbene by high-vacuum flash pyrolysis of ethyl 2-cyano-2-oxoacetate and subsequent trapping of the pyrolysate in an inert argon matrix at 3 K. After irradiation of the matrix with green light for a few seconds singlet \textit{trans}-cyanohydroxycarbene rearranges to its \textit{cis}-conformer. Prolonged irradiation leads to the formation of cyanoformaldehyde and isomeric isocyanoformaldehyde. \textit{Cis}- and \textit{trans}-cyanohydroxycarbene were characterized by matching matrix IR and UV/Vis spectroscopic data with \textit{ab initio} coupled cluster and TD-DFT computations. \textit{Trans}-cyanohydroxycarbene undergoes a conformer-specific [1,2]H-tunneling reaction through a 33.3 kcal/mol barrier (the highest penetrated barrier of all H-tunneling reactions observed to date) to cyanoformaldehyde with a half-life of 23.5 $\pm$ 0.5 d; this is the longest half-life reported for an H-tunneling process to date. During the tunneling reaction the \textit{cis}-conformer remains unchanged over the same period of time and the Curtin–Hammett principle does not apply. NIR irradiation of the O–H stretching overtone does not enhance the tunneling rate \textit{via} vibrational activation. Push–pull stabilization of hydroxycarbenes through \textit{s}- and \textit{p}-withdrawing groups therefore is even more stabilizing than push–push substitution.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

English

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http://hdl.handle.net/2142/107570

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