Dissociation Pathways of 2,3-Dihydrofuran Measured by Chirped-Pulse Fourier Transform Microwave Spectroscopy

This experiment combines the use of an ultrabroadband chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer with a pulsed discharge nozzle to study products formed during dissociation of 2,3-dihydrofuran (2,3-DHF). Molecules identified in the spectrum include cyclopropanecarboxaldehyde (CPCA), acrolein, crotonaldehyde (CA), formaldehyde, propene, propyne and cyclopropenylidene. Individual cis and trans isomers were detected for CPCA and acrolein, but only the trans isomer of CA was observed. Although cis forms of CPCA and CA would be the most likely structures produced from 2,3-DHF isomerization, our discharge provides enough energy for the molecules to convert into multiple conformers. The identification of formaldehyde in the spectrum supports a proposed mechanism to form propyne directly from 2,3-DHF ring-opening, a scheme that has been difficult to verify. Although acetylene cannot be detected because of the lack of a permanent dipole moment, the existence of cyclopropenylidene (C3H2) is in...