Se investigó el mecanismo y la cinética de pirolisis en fase gaseosa del 4-cloro-1-butanol a nivel DFT. La reacción da como productos tetrahidrofurano, formaldehido, propeno cloruro hidrogeno. El eliminación molecular sugiere dos vías reacción. primera vía se produce través un estado transición cíclico cuatro miembros, donde teoría WB97XD/6-31G++(d,p) mostró resultados cercanos con los parámetr...

In this paper we investigate (using AM1 semi-empirical as well as HF methods at the STO-3G, 3-21G, 6-31G, 6-31G* and 6-31+G** level) the conformations, geometrical parameters, Mulliken charges, and solvation effects of the triphosphate form of AZT (AZTTP), as well as the thymidine nucleotide (dTTP) structure. Our calculated geometrical parameters and Mulliken charges, with and without solvation...

Métodos compostos adaptados ao método ONIOM foram utilizados no cálculo teórico de afinidades por próton (PA) e eletrônica (EA) para um grupo de 50 moléculas (álcoois, cetonas, radicais e alcenos). A energia eletrônica foi descrita considerando-se o escalonamento de ZPE (λ) e a correção de alto nível (HLC). O valor ótimo para λ foi obtido através dos dados de PA. Os cálculos de EA foram utiliza...

Theoretical calculations have been performed for different possible hydrogen bonding complexes between adenine and hydrogen peroxide (AHP). The studied complexes (1-6) were cyclic ones showing two hydrogen bonds of different strength. All of the structures have been characterized at the B3LYP/6-31G(2d,p) and MP2(full)/6-31G(2d,p) levels, yielding only real frequencies (minima) at the B3LYP/6-31...

The relative reactivity of a series of nucleophiles that includes ethylene, sulfides, sulfoxides, amines, and phosphines toward dioxirane, dimethyldioxirane, carbonyloxide and dimethylcarbonyloxide has been U U Ž . U examined at the MP4r6-31G rrMP2r6-31G , QCISD T r6-31G rrMP2r631G , and B3-LYPr6-31G levels of theory. The barriers for the oxidations with Ž . dimethyldioxirane are higher up to 2...

To elucidate microscopic details of proton cancer therapy (PCT), we apply the simplest-level electron nuclear dynamics (SLEND) method to H+ + (H2O)1-6 at ELab = 100 keV. These systems are computationally tractable prototypes to simulate water radiolysis reactions-i.e. the PCT processes that generate the DNA-damaging species against cancerous cells. To capture incipient bulk-water effects, ten (...

Essential oils that contain large concentrations of germacrene D are typically accompanied by cadinane sesquiterpenoids. The acid-catalyzed cyclization of germacrene D to give cadinane and selinane sesquiterpenes has been computationally investigated using both density functional (B3LYP/6-31G(*)) and post Hartree-Fock (MP2/6-31G(* *)) ab initio methods. The calculated energies are in general ag...

The first total synthesis of the ramonanin family of lignan natural products is described. The short synthesis involves a 2,5-diaryl-3,4-dimethylene tetrahydrofuran intermediate, which participates in an unexpectedly facile Diels-Alder dimerization, generating all four natural products. Insights into the reactivity and stereoselectivity of the key dimerization are provided through computational...

[reaction: see text]. Dediazoniation of adeninediazonium ion, 1, forms the heteroaromatic cation, 2. Ab initio studies at the CCSD(fc)/6-31G**//MP2(full)/6-31G** level now reveal that the cyclic cation 2 is kinetically and thermodynamically unstable with respect to the pyrimidine ring-opened cation, 3. The results suggest that 4-cyano-5-isocyano-imidazole, 4, and 4,5-dicyanoimidazole, 5, might ...