Glassware for preparation of nitro reagent and diisocyanate urea derivatives. Reagent grade phosphoric acid. HPLC grade methanol, n-heptane, toluene, methylene chloride, isopropanol, hexane, acetonitrile, and isooctane. HPLC grade water. Standard preparation 3.3.1.
Undissolved residue is discarded.
Concentrate methylene chloride solution to 5 to 10 mL. Add a small amount n-heptane to start precipitation. The MDI precipitate is filtered and dried under vacuum. The precipitate formed is filtered and redissolved in a minimal volume of methylene chloride. Hexane is added to the solution to initiate precipitation. The precipitated MDI urea derivative is filtered and washed with methylene chloride.