PubMed · 15433985
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R BADER, P DIRHNUBER, F SCHUTZ. 1950. Cyanate-methaemoglobin.. https://doi.org/10.1016/0006-3002(50)90154-5
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The hypervalent iodine(III) reagent phenyliodine bis(trifluoroacetate) (PIFA) mediates the selective cyanation reactions of a wide range of electron-rich heteroaromatic compounds such as pyrroles, thiophenes, and indoles under mild conditions. These reactions proceed via a cation radical intermediate, and the key for the successful transformation presumably depends on the oxidation-reduction potential of the substrates used. The synthetic utility has been demonstrated through the conversion of these biologically important pyrroles 2f and 2g. [reaction: see text]
BACKGROUND: Isocyanates with the general formula R-(N=C=O) are theoretically contact sensitizers. However, allergic contact dermatitis (ACD) from isocyanates is seldom reported. In previous reports, patients reacted to their isocyanate-based work materials but not to commercial patch-test preparations of isocyanates. Therefore, we suspected that the low frequency of reported ACD from isocyanates was partly due to inadequate commercial preparations. A past study also showed the concentrations of diphenylmethane-4,4'-diisocyanate (4,4'-MDI) in petrolatum preparations to be much lower than declared. OBJECTIVE: In this study, 2,4-toluene diisocyanate (2,4-TDI), 1,6-hexamethylene diisocyanate (1,6-HDI), and isophorone diisocyanate (IPDI) were investigated in a similar fashion. METHODS: In preparations from 12 dermatology departments and two suppliers of patch-test allergens, we determined the isocyanate content as the isocyanate-dibutylamine derivative, using liquid chromatography and mass spectrometry. The preparations were considered stable if the ratio between the stated and found concentrations was within the range of 0.8 to 1.2. RESULTS: Although 28 of 36 investigated preparations had ratios outside of the stable range, they were in its vicinity, which indicates that preparations of 2,4-TDI, 1,6-HDI, and IPDI are more stable than are preparations of 4,4'-MDI where previously reported results showed ratios far outside of stable range. CONCLUSION: As opposed to preparations of 4,4'-MDI, preparations of 2,4-TDI, 1,6-HDI, and IPDI can be considered to be stable.
Aqueous dispersions of poly(ester-imide)s [P(E-I)s] have been prepared by dispersing the P(E-I)s in water without any external solubilizing agents. P(E-I)s were prepared from anhydride-terminated polyester prepolymer and diisocyanate. The -COOH groups in the polymer were then neutralized using triethylamine and the P(E-I)s were subsequently dispersed in water. The influence of the degree of ionization of polymers on the particle size and viscosity of the dispersion has been studied. The dispersions were crosslinked using polyaziridine. The crosslinked dispersion cast films were characterized for dynamic mechanical properties. As the ionic content increased the particle size decreased and the viscosity increased. When the amount of crosslinker added was varied, for a fixed percentage of ionization, the glass transition temperature Tg shifted to higher values. Critical surface tension (CST) measurements indicated reorganization of hydrophobic groups on the surface after crosslinking.