Ammonium carbamate type self-derivative salts of (R-)- and racemic α-methylbenzylamine: Composition and thermal stability by evolved gas analyses (TG-FTIR and TG/DTA-MS)

János Madarász, Edit Székely, Judit Halász, György Bánsághi, Dániel Varga, Béla Simándi, György Pokol

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Abstract

Two different compounds have formed from liquid enantiomeric (R-) and racemic α-methylbenzylamine (α-MBA, named also as 1-phenylethylamine, 1-FEA) with supercritical fluid CO2. The crystalline solids have been characterized by elemental CHN analysis, X-ray diffraction (XRD), FTIR, 1H, and 13C NMR spectroscopy, and found to be α-methylbenzylammonium α-methylbenzylcarbamate self-derivative ionic salts 1 (R/R) and 2 (rac RS), respectively, of the corresponding amines. Compound 2 (rac RS) has shown different XRD pattern from that of enantiomerically pure 1 (R/R), indicating a preferential formation of a 1:1 mixture of (R/S-) and (S/R-) or rather a racemate compound of (RS/SR-) ammonium carbamate salt (2 (rac RS)) from racemate. For thermal stability, the compounds have been checked by differential scanning calorimetry (DSC), simultaneous thermogravimetry and differential thermal analysis (TG/DTA), and in situ coupled evolved gas analysis by mass spectroscopy (TG/DTA-EGA-MS) and FTIR-gas cell (TG-FTIR). No melting point is observed because of the low thermal stability of the compounds. Decomposition stages are tried to be separated with using semi-closed (sealed with a pinhole on the top) crucibles, thus different evolution courses of CO2 and organic vapors could be followed by MS and FTIR spectroscopy. The α-MBA vapors themselves, evolved from open crucibles could be identified by FTIR-gas cell, while vapors up to m/z = 164 have been detected by MS from semi-closed Al crucible.

Original languageEnglish
Pages (from-to)567-574
Number of pages8
JournalJournal of Thermal Analysis and Calorimetry
Volume111
Issue number1
DOIs
Publication statusPublished - Jan 1 2013

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Keywords

  • Differential scanning calorimetry (DSC)
  • Evolved gas analysis (EGA)
  • FTIR spectroscopy
  • Mass spectrometry (MS)
  • Simultaneous TG/DTA
  • TG-FTIR
  • TG/DTA-MS
  • X-ray diffraction (XRD)

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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