Characterization of Low-Molecular Weight Iodine-Terminated Polyethylenes by Gas Chromatography/Mass Spectrometry and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry with the Use of Derivatization

Abstract

Gas chromatography/mass spectrometry (GC/MS) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry, in conjunction with various derivatization approaches, have been applied to structure determination of individual oligomers and molecular-mass distributions (MMD) in low-molecular mass polyethylene having an iodine terminus. Direct GC/MS analysis has shown that the samples under investigation composed of polyethyelene-iodides (major components) and n-alkanes. Exchange reaction with methanol in the presence of NaOH gave rise to methoxy-derivatives and n-alkenes. Electron ionization mass spectra have shown that the former contained terminal methoxy groups indicating the terminal position of the iodine atom in the initial oligomers. MMD parameters have been determined with the aid of MALDI mass spectrometry followed by preliminary derivatization-formation of covalently bonded charge through the reaction of iodides with triphenylphosphine, trialkylamines, pyridine or quinoline. The mass spectra revealed well-resolved peaks for cationic parts of derivatized oligomers allowing the determination of MMD. The latter values have been compared with those calculated from GC/MS data.

Catalytic activity of phenyl substituted cyclopentadienyl neodymium complexes in the ethylene oligomerization process

“…M n values, calculated from 1 H NMR spectra of PE-I and from MALDI-TOF mass-spectra of preliminary derivatized iodoalkanes [38], are generally in good agreement (see supporting information). …”

“…Iodo-functionalized oligoethylenes (PE-I), which could be easily analyzed by 1 H NMR spectroscopy [4,5] and by mass spectrometry with preliminary derivatization [38], have been analogously synthesized at 40ºC, using co-catalysts 2, 4, 6 and different Nd:Mg ratios (Scheme 4).…”

Regio-isomeric effects in tandem mass spectra of sulfonium cations generated from thiacyclane based sulfonium salts under soft ionization conditions

“…Some of them have been given in the book 4 and described in our recent papers. [6][7][8] One of the important types of compounds that are produced synthetically or are present in living bodies and caustobioliths is organic sulfides. Although lowmolecular-weight sulfides have been studied many times by electron and chemical ionization mass spectrometry, the need in their analysis and profiling using ''soft'' ionization methods can arise.…”

Simple approach to derivatization of alcohols and phenols for the analysis by matrix(surface)‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

“…The use of derivatization of analytes prior to analysis looks a very promising approach to enhance ionization efficiency and provide structural information. [1][2][3][4] Previously, we have shown that simple derivatization reactions such as silylation, acylation, alkylation, and imination were suitable for establishing some structural fragments of various types of analytes by MALDI-MS. [5][6][7][8][9] However, one of the most interesting derivatization techniques is based on the introduction of a fixed charge into an analyte molecule. [3,[9][10][11] Such methods are frequently used in combination with ESI-MS, in particular, for the analysis of peptides and proteins.…”

“…[1][2][3][4] Previously, we have shown that simple derivatization reactions such as silylation, acylation, alkylation, and imination were suitable for establishing some structural fragments of various types of analytes by MALDI-MS. [5][6][7][8][9] However, one of the most interesting derivatization techniques is based on the introduction of a fixed charge into an analyte molecule. [3,[9][10][11] Such methods are frequently used in combination with ESI-MS, in particular, for the analysis of peptides and proteins. One of the first papers in this field has described the use of two-step derivatization of the N-terminus in peptides by acylation with iodoacetic anhydride, iodoacetic acid or other haloacyl halides followed by treatment with various amines or triphenylphosphine to form quaternary ammonium or phosphonium salts, respectively.…”