The association reactions of Pb + ion with CH 3 OH and CH 3NH 2 in the gas phase

Abstract

Enthalpy, entropy, and Gibb's free energy changes for the ion/neutral association reactions Pb + (M) n−1 + M = Pb + (M) n where n = 1 or 2, and M is CH 3OH and CH 3NH 2, have been determined in the gas phase using a high pressure mass spectrometer technique. Like other Pb + ion complexes, the bonding of Pb + to the first two CH 3 OH and CH 3 NH 2 is much stronger than expected from simple electrostatic interaction considerations. A covalent interaction mechanism, as well as another model which considers that the bonding of small lead ion complexes is electrostatic in nature, but bonding is greatly enhanced by the hybridization of 6 s and 6 p orbitals of the Pb +, are discussed to interpret the results. From a thermochemical view, we expect that in the atmosphere there is an appreciable amount of lead ion clusters, containing one or two CH 3NH 2, and NH 3 along with Pb + water clusters. In addition, the thermochemical properties for the association reaction of Na + with CH 3NH 2 have also been determined. Enthalpy, entropy, and Gibb's free energy changes for the reaction are −Δ H 0 = 32.1 kcal mol −1, −Δ S 0 = 30.3 cal mol −1 K −1, and −Δ G 0 = 23.1 kcal mol −1, respectively.