The uncatalyzed reactions of 2,4-TDI (2,4-toluenediisocyanate) and MDI (4,4 0 -diphenylmethane-diisocyanate) with alcohols including butan-1-ol, butan-2-ol, diethylene glycol monomethylether (DEGME) were studied by high-performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS). The reactions were carried out at different temperatures from 22 C to 75 C using high molar ratios of alcohols to diisocyanates. It was found that the first isocyanate group of the MDI reacts about 1.5 times faster with the alcohols than the second one. The relative reactivities of the isocyanate groups (para and ortho) of 2,4-TDI as a function of the temperature was also deduced. From the temperature dependence of the rate constants the apparent activation energies were determined. Furthermore, the dependence of the apparent rate constant on the concentration of alcohols was also investigated and a mechanism was proposed for the reaction of diisocyanates with alcohols.
Residues of chemicals on clothing products were examined by direct analysis in real-time (DART) mass spectrometry. Our experiments have revealed the presence of more than 40 chemicals in 15 different clothing items. The identification was confirmed by DART tandem mass spectrometry (MS/MS) experiments for 14 compounds. The most commonly detected hazardous substances were nonylphenol ethoxylates (NPEs), phthalic acid esters (phthalates), amines released by azo dyes, and quinoline derivates. DART-MS was able to detect NPEs on the skin of the person wearing the clothing item contaminated by NPE residuals. Automated data acquisition and processing method was developed and tested for the recognition of NPE residues thereby reducing the analysis time.
A simple collision model for multiple collisions occurring in quadrupole type mass spectrometers was derived and tested with leucine enkaphalin a common mass spectrometric standard with well-characterized properties. Implementation of the collision model and Rice-Ramsperger-Kassel-Marcus (RRKM) algorithm into a spreadsheet software allowed a good fitting of the calculated data to the experimental survival yield (SY) versus collision energy curve. In addition, fitting also ensured to estimate the efficiencies of the kinetic to internal energy conversion for Leucine enkephalin in quadrupole-time-of-flight and triple quadrupole instruments. It was observed that the experimental SY versus collision energy curves for the leucine enkephalin can be described by the Rice-Ramsperger-Kassel (RRK) formalism by reducing the total degrees of freedom (DOF) to about one-fifth. Furthermore, this collision model with the RRK formalism was used to estimate the critical energy (E(o)) of lithiated polyethers, including polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetrahydrofurane (PTHF) with degrees of freedom similar to that of leucine enkephalin. Applying polyethers with similar DOF provided the elimination of the effect of DOF on the unimolecular reaction rate constant. The estimated value of E(o) for PEG showed a relatively good agreement with the value calculated by high-level quantum chemical calculations reported in the literature. Interestingly, it was also found that the E(o) values for the studied polyethers were similar.
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