There is an emerging consensus regarding the applicability of the kinetic method. All parties acknowledge that it is an approximate quantitative technique, capable of yielding not only enthalpy, but also entropy values. Opinions differ mainly on the accuracy of the results but it is agreed that the energy (effective temperature) dependence of kinetic method plots needs to be checked in all but the simplest of cases. When the 'apparent basicity' is found to depend on collision energy (and hence effective temperature), the extended kinetic method must be used. We have performed a large-scale modeling study, involving thousands of randomly selected molecular systems and a variety of experimental conditions, using exact calculations and realistic data sets. The results show that when the measured entropy difference between the two competing reaction channels is less than approximately 35 J mol(-1) K(-1), overall errors (standard deviations) of DeltaH(298) determined by the kinetic method are +/-5 kJ mol(-1); those of DeltaS(298) are +/-10 J mol(-1) K(-1). These include not only inherent errors of the kinetic method, but also errors in ion abundance measurement (5%) and inaccurate knowledge of reference compound thermochemistry (+/-2 kJ mol(-1), on average). We recommend, in general, that these errors be reported in kinetic method studies. When the measured entropy difference between the two competing fragmentation channels is large (>35 J mol(-1) K(-1)), it is likely to be significantly underestimated and errors of the kinetic method increase significantly.

Theoretical modeling of sustained off-resonance irradiation collision-induced dissociation (SORI-CID) experiments in Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry is described in the present paper. Manipulation of various analytical expressions yield the result that the average laboratory frame collision energy is equal to 2/3 of the maximum kinetic energy in SORI. Survival yields (the fraction of nondecomposed molecular ions) as a function of excitation time, collision energy, and source temperature have been considered: results of MassKinetics-type reaction kinetics modeling were compared with experimental results obtained by Guo et al. (Int. J. Mass Spectrom. 2003, 225, 71-82). The results show that radiative cooling has a major influence in SORI-CID. They also suggest that collisional cooling is significant only at very low (less than 0.02 eV) center of mass collision energy; therefore it has a very small influence on the SORI process. Survival yield curves showed excellent agreement between experiments and calculations optimizing two parameters only (collisional energy-transfer efficiency and radiative cooling rate). Using leucine enkephalin as a model compound, the results indicate 0.128 Ϯ 0.021 energy deposition in a single collision and 7.5 Ϯ 0.5 s Ϫ1 infrared cooling rate. We also present that these two physical parameters cannot be properly deconvoluted. This effect shows the importance of the parallel consideration of different physical processes.

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The synthesis of novel chiral monoaza-15-crown-5 compounds (1-4) with pyridine-ring starting from methyl-4,6-O-benzylidene-α-D-glucopyranoside and methyl-4,6-O-benzylidene-α-Dmannopyranoside by different methods are reported. These crown ethers showed significant asymmetric induction in a Michael addition (up to 80% ee).

We compared the microscopic structure of liquid water at ambient conditions predicted by six classical intermolecular potential models. Applying their accepted acronyms were the SPC (Simple Point Charge), SPC/E (SPC extended), MSPC/E (SPC/E modified), TIP4P (Transferable Intermolecular Potential, four point charges), TIP5P (TIP, five point charges), and the PPC (Polarizable Point Charge) intermolecular potential models. Configurations of computer simulations were used to study the structure at the level of partial three-particle correlation functions. We created contour maps for visual evaluation, calculated overlap integrals of the three-particle correlation functions of the models to quantify their similarity, and determined their distance-dependent three-particle entropy contribution. The SPC/E and the TIP4P water models generate quite similar structures, while the SPC and the MSPC/E pair exhibit the largest discrepancies. The structure of the PPC is the most ordered and the SPC structure is the most disordered among the studied interaction models.