En el presente trabajo de investigación se ha determinado nicotina en muestras de tabaco, correspondientes a marcas de cigarrillos nacionales, utilizando la destilación por arrastre de vapor y posterior determinación mediante espectrofotometría derivativa aplicando la técnica de la segunda derivada. El método de extracción es el sugerido por la Association of Official Analytical Chemists (AOAC). Sin embargo, para el análisis y expresión final de resultados, en este estudio se ha optado por utilizar la espectrofotometría derivativa por su simplicidad, sin requerir de una corrección de fondo. Los resultados están expresados en mg/L y % de alcaloides totales, y como nicotina.

We calculated the properties of nitratoxycarbon tetrahedrane derivatives using the methods:Hartree-Fock and density functional theory. We assessed structure, the electronic propertiesand energy profile to show Mulliken population analysis that the increase of nitratoxycarbongroups reduce the burdens of the oxygen’s of the group substituent.

The second-order nonlinear optical properties (NLO) of a set of copper phthalocyanines havebeen studied based on density functional theory calculations. Our calculations show thatthey possess high value NLO properties. The first hyperpolarizabilities can be enhanced byposition and number of donor-acceptor substituents along the phthalocyanine core.

This work identifies the structural and optical properties of species 4-amino-4'- nitrodiphenilsulfide such as: static dipole moment (ì), mean polarizability (á0), anisotropy of the polarizability (Äá) and the first hyperpolarizability average (â0). Data were obtained through the theory of the density functional, using B3LYP hybrid functional and feature 6- 31G basis.

This study analyzes the relationship that presents 11 aromatic compounds with heterocyclic Schiff bases and substituted in position meta and para with antioxidant activity, using the method UB3LYP/6-311G(d,p) within density functional theory.We determine the parameters: bond dissociation enthalpy (BDE), ionization potential (IP), protons dissociation enthalpy (PDE), affinity of protons (PA), electrons transfer enthalpy (ETE) and radical stabilization energy (RSE), all in gaseous phase. The results show that electrodonorssubstituents increases BDE when they are in position para, IP in position meta and para and ETE in position para. In addition, the electroatractors cause an increase in PDE and PA at position meta and para.

This paper discusses global descriptors such as hardness, electronegativity, nucleofilia and chemical potential and local reactivity indexes. We use the method of the density functional (DFT) to a level of calculation B3LYP/6-31G. With local reactivity indexes analyzed the nucleophile/electrophile character by the effect of substituents on the system 1,2-benzoquinone. With global descriptors of reactivity, we obtained acceptable correlations as well as the effect of substituents on the Uv-vis spectrum groups.

In this paper we analyze the most stable structure and the evolution of the reactivity of local using the indices of Fukui in systems phenolic substituted in position-para as amending function based on different methods. The results explain the substitutions: Electrophilic and aromatic nucleophilic and acylation in phenolic systems. The calculations were carried out at a level: HF/3-21G, B3LYP/3-21G, B3LYP/6-31G(d) and MP2/6-31+G(d), established the level of calculation for each type of reaction studied.