Nuclear Spin Isomers of Ethylene: Enrichment by Chemical Synthesis and Application for NMR Signal Enhancement

Abstract

Taking CH2CH2 for a spin: Enrichment of the nuclear spin isomers of ethylene was achieved by a catalytic reaction of acetylene with parahydrogen (see scheme). The spin isomers were used for NMR signal enhancement, both with and without subjecting them to a chemical reaction. The interconversion times of the nuclear spin isomers were evaluated at ambient pressure, thus revealing extremely long‐lived spin states with lifetimes of (1000±400) s.

Hyperpolarized NMR Spectroscopy: d‐DNP, PHIP, and SABRE Techniques

“…Another interesting substrate for heterogeneous hydrogenation with parahydrogen is acetylene. The product of this reaction is ethylene, which, in the case of a pairwise addition of pH 2 , is enriched with certain spin isomers . Such an enrichment cannot be detected by using NMR spectroscopy, owing to the magnetic equivalence of the hydrogen atoms in ethylene; however, if the magnetic equivalence is broken, direct NMR detection becomes possible.…”

“…The product of this reaction is ethylene, which, in the case of ap airwise addition of pH 2 ,i se nriched with certain spin isomers. [152] Such an enrichment cannotb ed etected by using NMR spectroscopy,o wing to the magnetic equivalence of the hydrogen atoms in ethylene;h owever,i ft he magnetic equivalence is broken, direct NMR detectionb ecomes possible. Zhivonitko et al showed that it was possible to obtain ah yperpolarized adduct with distinctive antiphase signals in the NMR spectra by adding perfluoro(para-tolylsulfenyl)chloride to ethylene, which was produced by the hydrogenation of acetylene with parahydrogen over aP d/TiO 2 catalyst.…”

NMR Hyperpolarization Techniques of Gases

“…15 min. [234] The further RD NMR development could concern utilization of such extremely long-lived HP. In addition, the progress achieved in the field of single-scan ultra-fast NMR techniques [235] also offers new capabilities, which earlier were considered incompatible with NMR hyperpolarization.…”

NMR Hyperpolarization Techniques of Gases

“…15 min. [233] The further RD NMR development could concern utilization of such extremely longlived HP. In addition, the progress achieved in the field of singlescan ultra-fast NMR techniques [234] also offers new capabilities, which earlier were considered incompatible with NMR hyperpolarization.…”