In general, if the atoms that make up the ring contain heteroatoms, such rings become heterocycles, and organic compounds containing heterocycles are called heterocyclic compounds. An article called 1H-31P HETCOR NMR elucidates the nature of acid sites in zeolite HZSM-5 probed with trimethylphosphine oxide, published in 2019, which mentions a compound: 676-96-0, Name is Trimethylphosphineoxide, Molecular C3H9OP, Product Details of 676-96-0.
Two-dimensional 1H-31P heteronuclear correlation NMR of trimethylphosphine oxide (TMPO) adsorbed in zeolites, in tandem with DFT calculations, challenges previous one-dimensional 31P NMR assignments, enabling the unambiguous discrimination of Bronsted and Lewis acid sites, extending the understanding of TMPO:Bronsted complexes formed with distinct stoichiometries at the HZSM-5 zeolite surface, and the proton-transfer mechanism.
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Reference:
Isoxazole – Wikipedia,
Isoxazole | C3H3NO – PubChem