Side reactions of phenylisocyanate in N,N‐dimethylacetamide

Abstract

SYNOPSISSide reactions of isocyanate groups in N,N-dimethylacetamide ( DMAC ) were studied. Although 4,4'-diphenylmethane diisocyanate (MDI) in DMAC was stable and no changes occurred at 3"C, the isocyanate content decreased and a gel was finally formed a t 40°C. Using phenyl isocyanate ( P I ) as a model compound of MDI, the identification of PI sidereaction products in DMAC were studied. From these experiments, the following five products were identified; ( 1 ) 1,3-diphenylurea (DPU ), ( 2 ) 1,3-diphenyl-5-phenylcarbamyl-6-dimethylaminouracil ( P U R ) , (3) 1,3,5-triphenylbiuret ( T P B ) , ( 4 ) triphenyl-s-triazine-2,4,6-trione (TTT), and ( 5 ) l,l-dimethyl-3-phenylurea (DMPU) . Among these identified products, the novel side reaction product PUR, which was formed between P I and DMAC as solvent, was found along with T P B and TTT, which were already known to cause threedimensional network formation.

Reactivity of isocyanates with urethanes: Conditions for allophanate formation

“…As assumed by Anzuino et al [25] and Matsui et al [26], the polar character of the solvent might be responsible for the relatively fast secondary reactions occurring in DMSO-d6. It should be noticed than the time required for the acquisition of the 13 C NMR spectrum is incompatible with the rapid evolution of the non neutralized products in DMSO-d6, contrary to some literature indications [28].…”

“…Authors found that the allophanate/urethane ratio increased with increasing [NCO]/[OH] ratio and temperature. Moreover, an isocyanate compound is not stable in this solvent, since Matsui [26] showed the cyclization of the isocyanate group in DMAc at 40°C. Matsui et al demonstrated that trimerization, which is known to be catalyzed by bases or metals, could take place slowly even without catalyst.…”

X-ray diffraction from low-dimensional structures

“…Si-doped GaAs normally considered to be of high structural quality is mosaic, although the relative orientations are i 10" (Fewster and Andrew 1993a). As we progress to crystals with dislocation densities -IO4 cm-' then we can see that the cellular structure typical ofsemi-insulating GaAs produces a significant relative orientation of -3 0 (Fewster 1991a, Matsui 1991. The blocks themselves are fairly perfect and approximately 5-10 mm in diameter.…”

Outstanding Poling Stability of a New Cross-Linked Nonlinear Optical (NLO) Material from a Low Molecular Weight Chromophore

“…The best approach to avoid thermal pretreatment and enhance NLO response seemed to be the use of reactive solvents with catalytic properties like N , N -dimethylacetamide (DMAC). It is known that DMAC reacts with isocyanates giving N , N -dimethylacetamidines whose further reaction leads to the formation of carbamides and cyclic products like isocyanurates, substituted barbituric acids, and aminouracils. , Some of these reactions occur at a significant rate even at room temperature due to the catalytic effect of DMAC itself. In fact rapid cross-linking of compound DMI 3 was observed when it was dissolved in DMAC after few hours.…”