Investigation of the competitive rate of derivatization of several secondary amines with phenylisocyanate (PHI), hexamethylene-1,6-diisocyanate (HDI), 4,4′-methylenebis(phenyl isocyanate) (MDI) and toluene diisocyanate (TDI) in liquid medium

Abstract

The stabilization of the isocyanate (NCO) groups during workplace sampling is necessary for their subsequent laboratory analysis. Most derivatization reagents are secondary amines. By carrying out a test in which two secondary amines are added to an isocyanate, the relative rates of these reactions can be evaluated. This evaluation is known for a monoisocyanate, phenylisocyanate (PHI), but is being developed for diisocyanates. This study deals with the relative reactivity (RR) of four diisocyanates: hexamethylene 1,6-diisocyanate (HDI), 4,4'-methylenebis(phenyl isocyanate) (MDI), and the ortho and para isomers of toluene diisocyanate (TDI) in addition to PHI, with four secondary amines: 1-(2-methoxyphenyl)piperazine (MOPIP), 9-(N-methylaminomethyl)anthracene (MAMA), 1-(9-anthracenylmethyl)piperazine (MAP), and dibutylamine (DBA). These competitive derivatization reactions are studied in three reaction solvents, namely acetonitrile, toluene, and acetonitrile doped with water (1% v/v). The results show that the order of reactivity, which doesn't change with the isocyanate as well as with the solvent used, is the following: DBA > MAP > MOPIP > MAMA. The relative difference in reactivity is a function of both the isocyanate and the solvent used. Hindered aromatic diisocyanates (TDI and MDI) show a greater difference in reactivity with the derivatization agents. These differences in reactivity are also modified by the solvent used. For example, larger differences are observed in acetonitrile than in toluene, but the introduction of water to acetonitrile, which does not affect the reaction yield, makes these differences smaller.

Synthesis of Highly Elastic Biodegradable Poly(urethane urea)

“…The reason for this is steric hindrance. 24 Here, LDI shows a higher reactivity for the isocyanate closest to the methyl ester substituent despite the expected steric hindrance. This could be explained by the fact that the ester group is an electronwithdrawing group, which would lead to an increase in the nucleophilicity of the isocyanate.…”

A Comparison of Two Sampling Methods for the Detection of Airborne Methylene Bisphenyl Diisocyanate

“…(5) Common derivatizing agents include tryptamine, 1-(2-methoxyphenyl) piperazine (MOPP), and 1-(9-anthracenylmethyl) piperazine (MAP) as listed in the NIOSH Manual of Analytical Methods for isocyanates; 9-(methylaminomethyl) anthracene (MAMA), which is used in the SKC Inc. Iso-Chek method; and, 1-(2-pyridyl) piperzine (1-2PP) as used in OSHA Method 47 for MDI. (26)(27)(28)(29) Tremblay et al (30) investigated competitive rates of derivatization of several secondary amines and isocyanates. Relative differences were observed in MDI reactivity.…”

One‐Step Synthesis of Biodegradable Polyurethane Prepolymer and Its Rapid Gelation Behavior at High Water Content

“…A typical synthesis scheme of PU prepolymer is shown in Figure A. Previous work had shown that the isocyanate group at position 4 was more reactive than that at position 2 (adjacent to the methyl group, only ≈12% of the reactivity of position 4) on the asymmetric TDI . Thus, we assumed that most of the hydroxyl groups of L‐PEG and F‐PCL reacted with the isocyanate group at position 4 and the structure shown in Figure A represented the majority components of the resultant prepolymer.…”