A direct dynamics simulation at the B3LYP/6-311+G(d,p) level of theory was used to study the F- + CH3OOH reaction dynamics. The simulations are in excellent agreement with a previous experimental study (J. Am. Chem. Soc. 2002, 124, 3196). Two product channels, HF + CH2O + OH- and HF + CH3OO-, are observed. The former dominates and occurs via an ECO2 mechanism in which F- attacks the CH3- group, abstracting a proton. Concertedly, a carbon-oxygen double bond is formed and OH- is eliminated. Somewhat surprisingly this is not the reaction path, predicted by the intrinsic reaction coordinate (IRC), which leads to a deep potential energy minimum for the CH2(OH)2...F- complex followed by dissociation to HF + CH2(OH)O-. None of the direct dynamics trajectories followed this path, which has an energy release of -63 kcal/mol and is considerably more exothermic than the ECO2 path whose energy release is -27 kcal/mol. Other product channels not observed, and which have a lower energy than that for the ECO2 path, are F- + CO + H2 + H2O (-43 kcal/mol), F- + CH2O + H2O (-51 kcal/mol), and F- + CH2(OH)2 (-60 kcal/mol). Formation of the CH3OOH...F- complex, with randomization of its internal energy, is important, and this complex dissociates via the ECO2 mechanism. Trajectories which form HF + CH3OO- are nonstatistical events and, for the 4 ps direct dynamics simulation, are not mediated by the CH3OOH...F- complex. Dissociation of this complex to form HF + CH3OO- may occur on longer time scales.

Classical trajectory simulations are performed to study energy transfer in collisions of protonated diglycine, gly 2 -H + , and dialanine, ala 2 -H + , ions with a fluorinated octanethiol self-assembled monolayer (F-SAM) surface for collision energies E i in the range of 5-70 eV and incident angles θ i of 0 and 45°with respect to the surface normal. Both explicit-atom (EA) and united-atom (UA) models were used to represent the F-SAM surface. The simulations show the distribution of energy transfer to the peptide-ion's internal degrees of freedom, ∆E int , to the surface, ∆E surf , and in peptide-ion translation, E f , are very similar for gly 2 -H + , and ala 2 -H + . The average percentage energy transferred to ∆E surf and E f increases and decreases, respectively, with an increase in E i , while the average percentage energy transfer to ∆E int is nearly independent of E i . Changing θ i from 0 to 45°decreases and increases the percentage of energy transfer to ∆E surf and E f , respectively, but has little change in the transfer to ∆E int . Average percentage energy transfer to the surface is found to approximately depend on E i according to exp(-b/E i ). Comparisons with previous simulations show that peptide-H + collisions with the EA F-SAM model transfer approximately a factor of 2 more energy to ∆E int than do collisions with the hydrogenated SAM, that is, H-SAM. Replacing the mass of the F atoms by that of a H atom in the simulations, without changing the potential, shows that the different ∆E int energy transfer efficiencies for the F-SAM and H-SAM surfaces is a mass effect. The simulations for ala 2 -H + colliding with the EA F-SAM surface give P(∆E int ) distributions in good agreement with previous experiments and an average transfer to ∆E int of 15% as compared with the experimental value of 21%. The UA F-SAM model gives energy transfer efficiencies in qualitative agreement with those of the EA model, but there are important quantitative differences.