Probing the Pyrolysis of Ethyl Formate in the Dilute Gas Phase by Synchrotron Radiation and Theory

AbstractThe thermal decomposition of the atmospheric constituent ethyl formate was studied by coupling flash pyrolysis with imaging photoelectron photoion coincidence (iPEPICO) spectroscopy using synchrotron VUV radiation at the Swiss Light Source (SLS). iPEPICO allows photoion mass-selected threshold photoelectron spectra (ms-TPES) to be obtained for pyrolysis products. By threshold photoionization and ion imaging, parent ions of neutral pyrolysis products and dissociative photoionization products could be distinguished, and multiple spectral carriers could be identified in several ms-TPES. The TPES and mass-selected TPES for ethyl formate are reported for the first time and appear to correspond to ionization of the lowest energy conformation having acis configuration of theO=C(H) –O–C(H2) –CH3 andtrans configuration of the O=C(H) –O–C(H2) –CH3 dihedral angles. We observed the following ethyl formate pyrolysis products: CH3CH2OH, CH3CHO, C2H6, C2H4, HC(O)OH, CH2O, CO2, and CO, with HC(O)OH and C2H4 pyrolyzing further, forming CO + H2O and C2H2 + H2.The reaction paths and energetics leading to these products, together with the products of two homolytic bond cleavage reactions, CH3CH2O · + ·CHO and CH3CH2· + HC(O)O·, were studied computationally at the M06-2X-GD3/aug-cc-pVTZ and SVECV-f12 levels of theory, complemented by further theoretical methods for comparison. The calculated reaction pathways were used to derive Arrhenius parameters for each reaction. The ...
Source: Journal of Mass Spectrometry - Category: Chemistry Authors: Tags: RESEARCH ARTICLE Source Type: research