Cation Affinities (cation + affinity)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Assessment of theoretical methods for the calculation of methyl cation affinities

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2008
Y. Wei
Abstract The methyl cation affinity (MCA; 298 K) of a variety of neutral and anionic bases has been examined computationally with a wide variety of theoretical methods. These include high-level composite procedures such as W1, G3, G3B3, and G2, conventional ab initio methods such as CCSD(T) and MP2, as well as a selection of density functional theory (DFT) methods. Experimental results for a variety of small model systems are well reproduced with practically all these methods, and the performance of DFT based methods are far superior in comparison to their MP2 analogs for these small models. For larger model, systems including motifs frequently encountered in organocatalysts, the performance deteriorates somewhat for DFT methods, while it improves significantly for MP2, rendering the former methods unreliable for common organic bases. Thus, MP2 calculations performed in combination with basis sets such as 6-31+G(2d, p) or larger, appear to offer a practical and reliable approach to compute MCAs of organic bases. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source]

A computational and experimental study of cation affinity (Na+) of nucleobases and modified nucleobases by electrospray ionization ion trap mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2004
S. Rochut
Gas-phase Na+ affinities of modified or unmodified nucleobases were determined theoretically at the density functional theory level, with the B3P86 functional and the 6,31,+,G* basis set, and experimentally using electrospray ionization ion trap mass spectrometry (ESI-ITMS) and the kinetic method. For the calculations, the sodium cation affinities (SCA) were obtained from energies of the most stable complexes of the free nucleobases. Experimentally and theoretically relative scales of cation affinities were determined using eight modified and unmodified nucleobases and a very good agreement was obtained. Copyright © 2004 John Wiley & Sons, Ltd. [source]