Acid catalysis by hydronium ions is ubiquitous in aqueous-phase organic reactions. Here we show that hydronium ion catalysis, exemplified by intramolecular dehydration of cyclohexanol, is markedly influenced by steric constraints, yielding turnover rates that increase by up to two orders of magnitude in tight confines relative to an aqueous solution of a Brønsted acid. The higher activities in ...

Seeking to minimize degradation of NADPH during storage, reagent preparation, and assays, we investigated the effects of pH, temperature, and ionic strength as well as the effects of phosphate and acetate. NADH was also included for comparison. Our results indicate that the rate of degradation of NADPH is proportional most importantly to temperature and concentrations of hydronium ion, but also...

To synthesize 4-chloro-5-methoxy-2-(b-trifluoroethyl)-3(2H)-pyridazinone (4), the reactions of 4-chloro-5-methoxy-3(2H)-pyridazinone (5) with RCH(2)CF(3)(R = I, TsO, MsO, TfO) in different solvents were studied. It was found that methyl group migration took place during this reaction. An oxonium salt 9 was suggested as the active intermediate for the formation of the byproduct 4-chloro-5-methox...

We present a first-principles study of the UO(3)·n(H(2)O) uranyl oxide hydrates, namely, schoepite (n = 2.25), metaschoepite (n = 2) and dehydrated metaschoepite (n = 1.75), which appear as the alteration U(VI) products of aqueous corrosion of nuclear fuel. For these compounds, the calculated enthalpy of formation is in good agreement with calorimetry and solubility measurements. We discuss the...

In the title compound, 2C12H20N2 (2+)·2H3O(+)·P6O18 (6-)·2H2O, a protonated water mol-ecule bridges the centrosymmetrical anionic P6O18 ring via O-H⋯O hydrogen bonds. The centrosymmetric hydrogen-bonded rings formed by four oxonium cations and four phosphate anions can be described by an R 4 (8)(36) graph-set motif. The ring motifs are connected by hydrogen bonds into inorganic layers perpendic...

The explicit contribution to the free energy barrier and proton conductance from the delocalized nature of the excess proton is examined in aquaporin channels using an accurate all-atom molecular dynamics computer simulation model. In particular, the channel permeation free energy profiles are calculated and compared for both a delocalized (fully Grotthuss shuttling) proton and a classical (non...

ABSTRACT: Composite mobility peak of multiple ion families in the atmosphere predicted by Mohnen [Mohnen, 1977] has analytically been obtained using a general solution of coupled diffusionreaction equations governing the spatiotemporal evolution of the number densities of an arbitrary number of ionic species. In model analysis at dynamic equilibrium, three discrete mobility spectra can be numer...

Molecular dynamics (MD) simulations are used to model changes in the conformational preferences of a model peptide during the transition from a hydrated environment (charged nanodroplet generated by electrospray ionization) to the solvent-free peptide ion. The charged droplet consists of ∼2400 water molecules, 22 hydronium ions, and 10 chloride and contains a single Substance P (SP) [SP + 3H]3+...