hydrogen is considered as a unique choice for future world’s resources. the important parameter in the process of hydrogen production is the value of reduction potential for the used catalyst, in direct contact with consumed energy in process. the application of computational methods to design and modify molecular catalysts is highly regarded. this study sought to explore density functional the...

High-level ab initio calculations have been performed on the exo and endo isomers of gas-phase tetrahydrodicyclopentadiene (THDCPD), a principal component of the jet fuel JP10, using the Gaussian G(x) and G(x)(MP(x)) composite methods, as well as the CBS-QB3 method, and using a variety of isodesmic and homodesmotic reaction schemes. The impetus for this work is to help resolve large discrepanci...

C₈₀ is a fullerene species which appears in different isomeric configurations. A general homodesmotic reaction previously designed to study the energy of fullerenes was implemented, in order to analyze the energy of this family of isomers. These results concur with some of the experimental data, but energy differences referring to all the configurations yield novel propositions about their part...

We have used an ab initio SCF molecular orbital approach in conjunction with the isodesmic reaction procedure to investigate anomalous energy effects in strained aza systems and some of their nitro derivatives. The introduction of nitrogens into strained molecular frameworks is found to confer added degrees of stability. In general this increases with the number of nitrogens in a series of simi...

The effect of various reaction schemes used to convert total reaction enthalpies obtained via ab initio methods into enthalpies of formation has been studied employing a new optimization technique. The reaction schemes, conventional, isostoichiometric, and isodesmic have been defined and generated for 47 species for which highly accurate experimental enthalpies of formation in addition to total...

An explicit application of isodesmic reaction (a proton exchange between the studied and similar in structure reference molecule), where the free energy change of the protonation reaction in water was obtained using the free energies in solution from a single continuum model, was used to predict stepwise protonation constants of nitrilotriacetic acid. Calculations were performed at the RB3LYP/6...

The present study focuses on important questions associated with modeling of peptide and protein stability. Computing at different levels of theory (RHF, B3LYP) for a representative ensemble of conformers of di- and tripeptides of alanine, we found that the Gibbs Free Energy values correlate significantly with the total electronic energy of the molecules (0.922 < or = R2). For noncovalently att...

Exactly solvable models of linear aggregation have been known since Ising's seminal one-dimensional model. This model is defined by a unique nearest-neighbor bond strength that is independent of the length of the cluster; known as isodesmic symmetry. Linear aggregation in real systems has often been associated with broken isodesmic symmetry. Here we show that important examples can be mapped to...

Isodesmic energy comparisons of 6-31G*//6-31GS calculations for the fulvenes 1-3 and fulvenones 4-6 show significant destabilization for triafulvenone (4, -1 7.1 kcal) and heptafulvenone (6, -5.1 kcal/mol) and stabilization for pentafulvenone (5,4.1 kcal/mol). These effects are attributed to enhanced antiaromatic destabilization in 4 and 6 compared to the corresponding fulvenes and enhanced aro...

Intramolecular CF···FC interactions in selected organofluorine compounds (all-syn-1,2,3,4- and all-syn-1,2,4,5-tetrafluorocyclohexane, 1,8-difluoronaphthalene, 4,5-difluorophenanthrene, 2,2',5,5'-tetrafluorobiphenyl) were studied at the MP2/aug-cc-pVDZ level using the recently developed noncovalent interaction (NCI) method. For the optimized minima, all CF···FC interactions that are identified ...