Confirmation of the presence of formaldehyde and N-(methylene)morpholiniumcations as reactive species in the cellulose/NMMO/water system by trappingreactions

The presence of formaldehyde (4) in solutions of cellulose in N-methylmorph oline-N-oxide (NMMO, 1) has been shown by trapping formaldehyde as dimedone adduct 8 in a two-phase system, o-Dichlorobenzene was used as an inert sol vent to extract the trapping product as soon as it had formed. Morpholine is a degradation product of NMMO and is always present in system s containing NMMO. Formaldehyde can react with morpholine to form an interm ediate carbenium-iminium ion, N-(methylene)morpholinium (6). The occurrence of 6 in the system cellulose/NMMO was demonstrated by trapping this interm ediate in a Mannich type reaction with 2-acetonaphthone (9). Both formaldeh yde and N-(methylene)morpholinium cations are highly reactive species readi ly undergoing further reactions with nucleophiles. These processes might co ntribute to the observed discoloration of the reaction mixture, and might a lso be responsible for the decomposition of NMMO that is inducible by carbe nium-iminium ions.