Binding Energies of Proton-Bound Ether/Alcohol Mixed Dimers Determined by FTICR Radiative Association Kinetics Measurements

Abstract

The reactions of protonated diethyl ether with ethanol and protonated di-n-propyl ether with n-propanol, producing the mixed proton-bound dimers, were studied at low pressures in a FTICR cell. The pressure dependence of the apparent rate constant for proton-bound dimer formation was investigated and yielded unimolecular dissociation rate constants, kb, and photon emission rate constants, kra, for the nascent proton-bound dimers at internal energies equal to the dissociation energies of the dimers. The experimental kra values were found to be 17 ± 3 and 6.3 ± 0.6 s-1, respectively, for the ethanol/diethyl ether and n-propanol/di-n-propyl ether proton-bound dimers. RRKM modeling of the unimolecular dissociation rate constants as a function of the binding energies yielded the 0 K dissociation energies of the proton-bound dimers as 109 ± 1 and 105.1 ± 0.6 kJ mol-1 for the ethanol/diethyl ether and n-propanol/di-n-propyl ether proton-bound dimers, respectively. Using B3LYP/6-311G** thermal energies, the corres...