A reação em meio aquoso alcalino do dibrometo de 1,3-bis(4-cianopiridinium)propano, um composto constituído por dois anéis piridínicos conectados por uma ponte metilênica de três carbonos, gerou um novo composto, o 1-(4-ciano-2-oxo-1,2-diidro-1-piridil)-3-(4-ciano-1,2-diidro-1-piridil)propano. O resultado da reação é atribuído à proximidade do íon OH -, encapsulado entre os dois anéis piridínicos, fato este observado apenas em derivados bis-piridínicos conectados por pontes metilênicas de curta extensão, onde imperam efeitos de carga aliados à conformação.The aqueous alkaline reaction of 1,3-bis(4-cyanopyridinium)propane dibromide, a reactant constituted of two pyridinium rings linked by a three-methylene bridge, generates a novel compound, 1-(4-cyano-2-oxo-1,2-dihydro-1-pyridyl)-3-(4-cyano-1,2-dihydro-1-pyridyl)propane. The reaction pathway is attributed to the proximity of the OH -ion inserted between two pyridinium moieties, which occurs only in bis(pyridinium) derivatives connected by short methylene spacers, where charge-conformational effects are important.

The alkaline hydrolysis of a series of homologous reactants constituted by two reactive centers bridged by a methylene spacers chain, the 1,n-bis(2-azidepyridinium)alkanes (n = 3, 4, 5, 6, and 8), is investigated. The reaction under pseudo-first-order condition was followed by ultraviolet-visible spectrophotometry. The presence of clear isosbestic point suggests the absence of stable intermediates. However, the intermediates 1-(2-azidepyridinium), n-(2-pyridone)alkanes (monocationic compounds), were isolated and characterized as well the reaction end products 1,n-(2-pyridone)alkanes (noncharged compounds). The kinetic analysis fitted to a two-step consecutive reaction, where the k 1 /k 2 values demonstrate the larger reactivity of the first step over the second one, especially for shorter bridged reactants. The OH − reaction order is one for each step. Although Debye-Hückel law was obeyed, the experimental point at ionic strength zero is much higher than the extrapolated one. In addition, the k 1 values substantially decrease as KCl is added especially for shorter homologous whereas the effect on k 2 is almost negligible. Simple charge density effects as a function of the spacer's length do not explain the observations. On the other hand, from the pronounced anion selectivity inhibition effects on k 1 for the shorter derivatives, the existence of an equilibrium involving a conformer, a "sandwich-type" complex with the OH − between the two pyridinium rings, with an "open-stretched" conformer is proposed. For short-bridged reactants, the complex conformer

The alkaline hydrolysis reaction rates of 1,n-bis(4-cyanopyridinium)alkane derivatives C n bis(CP) 2+ with n = 3, 6, and 8 were studied and compared to the reaction rate of the N-methyl-4-cyanopyridinium (MCP + ). C 6 bis(CP) 2+ and C 8 bis(CP) 2+ obeyed the first-order kinetic law. However for C 3 bis(CP) 2+ data fitted to a consecutive two-step model reaction, the observed rate constants (k obs ) of C 8 bis(CP) 2+ and C 6 bis(CP) 2+ are approximately 50% and 100%, respectively, higher than those for MCP + , an effect mainly assigned to the higher charge density of these two derivatives. For C 3 bis(CP) 2+ , the k obs of the second (slow) step is almost twofold the value observed for C 6 bis(CP) 2+ , whereas the first (fast) step is approximately six times higher. As for MCP, the hydrolysis of C n bis(CP) 2+ generates pyridone (P o ) and carbamidopyridinium (A + ) units. For C 3 bis(CP) 2+ , however at pHs above 11.5, one additional product is formed. From the existence of the new product and the kinetic evidence, a "sandwichedtype" complex with the OH − inserted between the rings is proposed. This structural effect in the C 3 bis(CP) 2+ due to the conformational effect justifies the (i) two kinetic steps, (ii) high rate constants, (iii) high P o /A + ratios, (iv) observed temperature and salt effects, and (v) the formation of the new product. C 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 478-486, 2013

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Life Cycle Assessment (LCA) is a tool that considers and quantifies the consumption of resources and the environmental impacts associated with a product, process or system during its life cycle, contributing to a better assessment of the overall performance and providing contributions relating to different stages of the life cycle, thereby allowing an indication of the overall performance of the systems. From this perspective, the article characterizes and analyses environmental impacts of different scenarios of water use in buildings by LCA. The analysis of environmental impacts was performed using SimaPro7.3.2 software and the IMPAC2002 + method. The results obtained made it easier to identify existing problems from the environmental perspective, promoting sustainable management with environmental and human health improvements.