Boc-DL-Arg-OH HCl H2O

The dynamics and mode specificity of the HCl + OH → Cl + H2O reaction are investigated using a full-dimensional quantum dynamics method on an accurate global potential energy surface. It is shown that the vibrational excitation of the HCl reactant greatly enhances the reactivity while the OH vibrational excitation has little effect. The surprising HCl vibrational enhancement of this early barrier reaction contradicts a naive extension of Polanyi's rules, but can be explained by the sudden vector projection model, which attributes the promotional effect of the HCl vibration to its strong coupling with the reaction coordinate at the transition state. In addition, it is found that the fundamental and overtone excitations of the HCl reactant change the reaction mechanism from a direct barrier crossing process to a capture-like process.

We report the discovery of a potentially useful superconcentrated HCl at ambient temperature and pressure by using a simple surfactant-based reversed micelle system. Surprisingly, the molar ratios of H(+) to H(2)O (denoted as n(H+)/n(H2O)) in superconcentrated HCl can be larger than 5, while the maximum achievable n(H+)/n(H2O) value for conventional saturated HCl aqueous solution (37 wt %) is only about 0.28. Furthermore, both NMR and FT-IR results indicate that a significant amount of HCl remains in the molecular form rather than being ionized into H(+) and Cl(-). The superconcentrated HCl may promote some organic reactions that are not feasible by using conventional 37 wt % HCl solution. For example, addition reaction between C═C and HCl occurs in superconcentrated HCl solution without using catalysts.

The entrance complex, transition state, and exit complex for the title reaction have been investigated using the CCSD(T) method with correlation consistent basis sets up to cc-pVQZ. The stationary point geometries for the reaction are related to but different from those for the water monomer reaction HCl + OH → Cl + H2O. Our most important conclusion is that the hydrogen-bonded water molecule removes the classical barrier entirely. For the endothermic reverse reaction Cl + (H2O)2, the second water molecule lowers the relative energies of the entrance complex, transition state, and exit complex by about 4 kcal/mol. The title reaction is exothermic by 17.7 kcal/mol. The entrance complex HCl⋯OH·(H2O) is bound by 6.9 kcal/mol relative to the separated reactants. The classical barrier height for the reverse reaction is predicted to be 16.5 kcal/mol. The exit complex Cl⋯(H2O)2 is found to lie 6.8 kcal/mol below the separated products. The potential energy surface for the Cl + (H2O)2 reaction is radically different from that for the valence isoelectronic F + (H2O)2 system.