Manipulating Stereoselectivity of Parahydrogen Addition to Acetylene to Unravel Interconversion of Ethylene Nuclear Spin Isomers
Full article
| Journal |
PCCP: Physical Chemistry Chemical Physics
ISSN: 1463-9076
, E-ISSN: 1463-9084
|
| Output data |
Year: 2024,
Volume: 26,
Number: 9,
Pages: 7821-7829
Pages count
: 9
DOI:
10.1039/d3cp04983c
|
| Tags |
Acetylene; Catalysts; Iridium compounds; Isomers; Lighting; Nuclear magnetic resonance spectroscopy; Stereoselectivity |
| Authors |
Sviyazov Sergey V.
1,2
,
Babenko Simon V.
1,3
,
Skovpin Ivan V.
1
,
Kovtunova Larisa M.
1,4
,
Chukanov Nikita V.
1,2
,
Stakheev Alexander Yu.
5
,
Burueva Dudari B.
1
,
Koptyug Igor V.
1
|
| Affiliations |
| 1 |
Laboratory of Magnetic Resonance Microimaging, International Tomography Center, SB RAS, Novosibirsk 630090, Russia
|
| 2 |
Novosibirsk State University, Novosibirsk 630090, Russia
|
| 3 |
V.V. Voevodsky Institute of Chemical Kinetics and Combustion, SB RAS, Novosibirsk 630090, Russia
|
| 4 |
Boreskov Institute of Catalysis, SB RAS, Novosibirsk 630090, Russia
|
| 5 |
N.D. Zelinsky Institute of Organic Chemistry, RAS, Moscow 119991, Russia
|
|
Funding (1)
|
1
|
Russian Science Foundation
|
23-23-00394
|
Symmetric molecules exist as distinct nuclear spin isomers (NSIMs). A deeper understanding of their properties, including interconversion of different NSIMs, requires efficient techniques for NSIM enrichment. In this work, selective hydrogenation of acetylene with parahydrogen (p-H2) was used to achieve the enrichment of ethylene NSIMs and to study their equilibration processes. The effect of the stereoselectivity of H2 addition to acetylene on the imbalance of ethylene NSIMs was experimentally demonstrated by using three different heterogeneous catalysts (an immobilized Ir complex and two supported Pd catalysts). The interconversion of NSIMs with time during ethylene storage was studied using NMR spectroscopy by reacting ethylene with bromine water, which rendered the p-H2-derived protons in the produced 2-bromoethan(2H)ol (BrEtOD) magnetically inequivalent, thereby revealing the non-equilibrium nuclear spin order of ethylene. A thorough analysis of the shape and transformation of the 1H NMR spectra of hyperpolarized BrEtOD allowed us to reveal the initial distribution of produced ethylene NSIMs and their equilibration processes. Comparison of the results obtained with three different catalysts was key to properly attributing the derived characteristic time constants to different ethylene NSIM interconversion processes: ∼3–6 s for interconversion between NSIMs with the same inversion symmetry (i.e., within g or u manifolds) and ∼1700–2200 s between NSIMs with different inversion symmetries (i.e., between g and u manifolds).