Tremblay Patrice, Lesage Jacques, Ostiguy Claude, Tra Huu Van
Université du Québec à Montréal (UQAM), Département de chimie et biochimie, C.P. 8888, Succ. Centre-Ville, Montréal, Canada H3C 3P8.
Analyst. 2003 Feb;128(2):142-9. doi: 10.1039/b209779f.
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.
在工作场所采样期间稳定异氰酸酯（NCO）基团对于其后续的实验室分析是必要的。大多数衍生化试剂是仲胺。通过进行向异氰酸酯中添加两种仲胺的测试，可以评估这些反应的相对速率。对于单异氰酸酯苯基异氰酸酯（PHI），这种评估是已知的，但正在针对二异氰酸酯进行开发。本研究涉及四种二异氰酸酯：六亚甲基1,6 - 二异氰酸酯（HDI）、4,4'-亚甲基双（苯基异氰酸酯）（MDI）以及甲苯二异氰酸酯（TDI）的邻位和对位异构体，除了PHI之外，还涉及四种仲胺：1 - （2 - 甲氧基苯基）哌嗪（MOPIP）、9 - （N - 甲基氨基甲基）蒽（MAMA）、1 - （9 - 蒽基甲基）哌嗪（MAP）和二丁胺（DBA）。这些竞争性衍生化反应在三种反应溶剂中进行研究，即乙腈、甲苯以及掺杂水（1% v/v）的乙腈。结果表明，反应活性顺序不随异氰酸酯以及所用溶剂而变化，如下所示：DBA > MAP > MOPIP > MAMA。反应活性的相对差异是所用异氰酸酯和溶剂两者的函数。受阻芳族二异氰酸酯（TDI和MDI）与衍生化试剂的反应活性差异更大。这些反应活性差异也会因所用溶剂而改变。例如，在乙腈中观察到的差异比在甲苯中更大，但向乙腈中引入水（这不会影响反应产率）会使这些差异变小。
