Structural Characterization of Methylenedianiline Regioisomers by Ion Mobility-Mass Spectrometry and Tandem Mass Spectrometry. 4. 3‑Ring and 4‑Ring Isomers

• Published in: Analytical chemistry (Washington) Vol. 90; no. 24; pp. 14453 - 14461
• Main Authors: Crescentini, Tiffany M, Stow, Sarah M, Forsythe, Jay G, May, Jody C, McLean, John A, Hercules, David M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 18.12.2018
• Subjects: Addition polymerization; Analytical chemistry; Aniline Compounds - chemistry; Chemistry; Desorption; Ion Mobility Spectrometry; Ionic mobility; Ionization; Isomers; Mass spectrometry; Mass spectroscopy; Methylene dianiline; Mobility; Polyurethane; Polyurethane resins; Precursors; Spectroscopy; Stereoisomerism; Structural analysis; Tandem Mass Spectrometry
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/acs.analchem.8b04103

Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) is used to characterize methylenedianiline (MDA) 3-ring and 4-ring species. Building on our previous MALDI-MS 2-ring MDA isomer study, here we compare 3-ring and 4-ring electrospray ionization (ESI) and MALDI results. In ESI, 3-ring and 4-ring MDAs each form a single [M + H]+ parent ion. However, in MALDI, each MDA multimer forms three unique precursor ions: [M + H]+, [M•]+, and [M – H]+. In this study, 3-ring and 4-ring MDA precursors are characterized to identify the unique fragment ions formed and their respective fragmentation pathways. In addition to the three possible precursors, the 3-ring and 4-ring species are higher-order oligomer precursors in polyurethane (PUR) production and thus provide additional insight into the polymeric behavior of these PUR hard block precursors. The combination of ion mobility-mass spectrometry (IM – MS) and tandem mass spectrometry (MS/MS) allow the structural characterization of these larger MDA multimers.