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The quaternization reaction between 2-amino-1-methylbenzimidazole and iodomethane was investigated in the gas phase and in liquid acetonitrile. Both experimental and theoretical techniques were used in this study. In the experimental part of this work, accurate second-order rate constants were obtained for this reaction in acetonitrile from conductivity data in the 293-323 K temperature range and at ambient pressure. From two different empirical equations describing the effect of temperature on reaction rates, thermodynamic functions of activation were calculated. In the theoretical part of this work, the mechanism of this reaction was investigated in the gas phase and in acetonitrile. Two different quantum levels (B3LYP/[6-311++G(3df,3pd)/LanL2DZ]//B3LYP/[6-31G(d)/LanL2DZ] and B3LYP/[6-311++G(3df,3pd)/LanL2DZ]//B3LYP/[6-31+G(d)/LanL2DZ]) were used in the calculations, and the acetonitrile environment was modeled using the polarized continuum model (PCM). In addition, an atoms in molecules (AIM) analysis was made aiming to characterize possible hydrogen bonding. The results obtained by both techniques are in excellent agreement and lead to new insight into the mechanism of the reaction under examination. These include the identification and thermodynamic characterization of the relevant stationary species, the rationalization of the mechanistic role played by the solvent and the amine group adjacent to the nucleophile nitrogen atom, the proposal of alternative paths on the modeled potential energy surfaces, and the origin of the marked non-Arrhenius behavior of the kinetic data in solvent acetonitrile. In particular, the AIM analysis confirmed the operation of intermolecular hydrogen bonds between reactants and between products, both in the gas phase and in solution. It is also concluded that the unusual solvent effect on this Menshutkin reaction stems from the conjunction of a nucleophile possessing a relatively complex chemical structure with a dipolar aprotic solvent that is protophobic.

The effect of high pressure processing (HPP), at different combinations of pressure and time, on dry fermented sausages (DFS) was evaluated by chemical, microbiological and sensory analyses. Lipid composition and stability were also assessed. HPP (N 400 MPa and longer than 154 s) produced a reduction in spoilage microbiota, without negative effect on fermentative microbiota, that will be able to continue their role. Total fatty acids and lipid stability were not affected. Only a small effect on fatty acid (FA) composition was observed. Nutritional value of the lipid fraction was only affected by the ratio n−6/n−3 FA. Treatments at 400 MPa for 154 s or 960 s resulted in DFS being detected as different from control by sensory analysis. Those differences did not depreciate the product; on the contrary it seems to improve the bright aspect of the whole sausage, the cohesion and firmness and the correctly dried aspect of slices. Industrial relevance: Dry fermented meat sausages are very popular ready-to-eat meat based products. This study assesses the effects of HPP on this much appreciated traditional products. The results showed that HPP can be successfully applied to these Mediterranean fermented products without losses of sensory and nutritional characteristics. The modelling and optimization of the HPP process applied on dry fermented sausages demonstrated in this study are an advantage to industry efficiency. The utilisation of HPP by the industry can significantly increase dry fermented meat sausage shelf life and safety, providing it an opportunity to reach the global market.

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