Trimethylphosphine oxide is a common side product in organic synthesis, including the Wittig, Staudinger, Mitsunobu reactions and also in the manufacture of triphenylphosphine. It is a popular reagent to induce the crystallization of various chemical compounds. It acts as an excellent ligand for hard metal centers. It can react with 9-methyl-9-azonianthracene methyl sulfate to get (10-methyl-9,10-dihydro-acridin-9-yl)-phosphonic acid dimethyl ester using sodium iodide and acetonitrile as solvent.