A Mass Spectrometry Experiment on the Degrees of Freedom Effect

• David Z. Keifer ^[1] ; Jose I. Juncosa Jr. ^[1]
  1. [1] Salisbury University

     Salisbury University

     Estados Unidos

     
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 101, Nº 9, 2024, págs. 3975-3982
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • An experiment is described that allows students to investigate the physical chemistry involved in unimolecular fragmentation and to explain their experimental results using Rice–Ramsperger–Kassel (RRK) theory. For the experiment, students prepare a solution of a series of homologous analytes and collect mass spectra of those analytes using GC-MS. All the analytes undergo the same three-step fragmentation in the mass spectrometer. The relative peak intensities from the ions in the fragmentation scheme are plotted as a function of the vibrational degrees of freedom of the molecular ions’ R group. Trends in these plots can be explained using concepts from RRK theory and highlight the “degrees of freedom effect” in mass spectrometry. The experiment is suitable for a variety of upper-level, undergraduate chemistry laboratories.