Journalartikel

Jahr der Veröffentlichung: 2019

Seiten: 802-808

Zeitschrift: Chemical Science

Bandnummer: 10

Heftnummer: 3

ISSN: 2041-6520

Open Access Status: Gold

DOI Link: https://doi.org/10.1039/c8sc03720e

Verlag: Royal Society of Chemistry

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 trans-cyanohydroxycarbene rearranges to its cis-conformer. Prolonged irradiation leads to the formation of cyanoformaldehyde and isomeric isocyanoformaldehyde. Cis-and trans-cyanohydroxycarbene were characterized by matching matrix IR and UV/Vis spectroscopic data with ab initio coupled cluster and TD-DFT computations. Trans-cyanohydroxycarbene undergoes a conformer-specific [1,2] H-tunnelling reaction through a 33.3 kcal mol(-1) barrier (the highest penetrated barrier of all H-tunnelling reactions observed to date) to cyanoformaldehyde with a half-life of 23.5 +/- 0.5 d; this is the longest half-life reported for an H-tunnelling process to date. During the tunnelling reaction the 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 tunnelling rate via vibrational activation. Push-pull stabilisation of hydroxycarbenes through sigma- and pi-withdrawing groups therefore is even more stabilizing than push-push substitution.

Harvard-Zitierstil: Eckhardt, A., Erb, F. and Schreiner, P. (2019) Conformer-specific [1,2]H-tunnelling in captodatively-stabilized cyanohydroxycarbene (NC-C''-OH), Chemical Science, 10(3), pp. 802-808. https://doi.org/10.1039/c8sc03720e

APA-Zitierstil: Eckhardt, A., Erb, F., & Schreiner, P. (2019). Conformer-specific [1,2]H-tunnelling in captodatively-stabilized cyanohydroxycarbene (NC-C''-OH). Chemical Science. 10(3), 802-808. https://doi.org/10.1039/c8sc03720e