Synchrotron Photoionization Investigation of the Oxidation of Ethyl tert-Butyl Ether

The oxidation of ethyl tert-butyl ether (ETBE), a widely used fuel oxygenated additive, is investigated using Cl atoms as initiators in the presence of oxygen. The reaction is carried out at 293, 550, and 700 K. Reaction products are probed by a multiplexed chemical kinetics photoionization mass spectrometer coupled with the synchrotron radiation produced at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory. Products are identified on the basis of mass-to-charge ratio, ionization energies, and shape of photoionization spectra. Reaction pathways are proposed together with detected primary products.

Tunneling in the loss of hydrogen chloride from isopropyl chloride cation

The unimolecular dissociation of isopropyl chloride cation has been investigated using mass-analyzed ion kinetic energy spectrometry. The C3H6*+ ion was the only product ion in the metastable dissociation. The kinetic energy release distribution for the HCl loss was determined. Ab initio molecular orbital calculations were performed at the MP2/6-311++G(d,p) level together with single point energy calculations at the QCSID(T)/6-311++G(2d,2p) level. The calculations show that the molecular ion rearranges to an ion-dipole complex prior to loss of HCl via a transition state containing a four-membered ring. The rearrangement involves H atom transfer. On the basis of the potential energy surface obtained for the loss of HCl and Cl*, the rate constants were calculated by transition-state statistical theories with considering tunneling effect. From the calculated result, it is proposed that the observed HCl loss would occur via tunneling through the barrier for isomerization to the ion-dipole complex, CH3CHCH2*+...HCl.