This paper reports the influence of reaction temperature on the occurrence and characteristics of pH oscillations that are observed during the palladium-catalysed phenylacetylene oxidative carbonylation reaction in a catalytic system (PdI2, KI, air, NaOAc) in methanol. Isothermal experiments were performed over the temperature range 10-50 degrees C. The experiments demonstrate that oscillations occur in the range 10-40 degrees C and that a decrease in reaction temperature results in an increase in the period and amplitude of the pH oscillations. Furthermore, it is observed that during oscillations at any specific temperature, the time taken for pH to increase from a minimum to a maximum value varies with respect to reaction time. However, the time required for the pH to fall from maximum to new minimum is approximately constant with respect to the reaction time and is a function of the reaction temperature.

This paper reports on the influence of oscillations on product selectivity as well as the dynamics of product formation during the palladium-catalysed phenylacetylene oxidative carbonylation reaction in a catalytic system (PdI2, KI, Air, NaOAc in methanol). The occurrence of the pH oscillations is related to PdI2 granularity and the initial pH drop after phenylacetylene addition. To achieve pH and reaction exotherm oscillations regulation of the amount of PdI2 is required, ensuring that the initial pH does not fall significantly below 1 after phenylacetylene addition. Experiments in both oscillatory and non-oscillatory pH regimes were performed in an HEL SIMULAR reaction calorimeter with the concentration-time profiles measured using a GC-MS. It is demonstrated that when operating in an oscillatory pH regime product formation may be suppressed until oscillations occur after which there is a steep increase in the formation of Z-2-phenyl-but-2-enedioic acid dimethyl ester. When operating in non-oscillatory pH mode the products are formed steadily over time with the main products being Z-2-phenyl-but-2-enedioic acid dimethyl ester, 2-phenyl-acrylic acid methyl ester and E-3-phenyl-acrylic acid methyl ester.

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The cystic fibrosis transmembrane conductance regulator (CFTR) is vital for Cl ؊ and HCO 3 ؊ transport in many epithelia. As the HCO 3 ؊ concentration in epithelial secretions varies and can reach as high as 140 mM, the lumen-facing domains of CFTR are exposed to large reciprocal variations in Cl ؊ and HCO 3 ؊ levels. We have investigated whether changes in the extracellular anionic environment affects the activity of CFTR using the patch clamp technique. In fast whole cell current recordings, the replacement of 100 mM external Cystic fibrosis transmembrane conductance regulator (CFTR) 1 is a cyclic AMP activated epithelial Cl Ϫ channel, the mutation of which causes the potentially fatal inherited disease cystic fibrosis (CF) (1). The CFTR protein is a member of the ABC transporter family and is regulated by phosphorylation (2-4) and by ATP binding and hydrolysis (5-7). Dephosphorylation of CFTR by membrane-bound protein phosphatases is also important in the physiological regulation of channel activity (2,8,9).Although CF is generally considered to result from a defect in Cl Ϫ transport, most of the affected epithelia also transport HCO 3 Ϫ ions. Indeed, recent work suggests that there is a better correlation between defects in CFTR-dependent HCO 3 Ϫ transport than defects in Cl Ϫ transport and the severity of disease (10). HCO 3 Ϫ is an important component of epithelial secretions and, via its buffering role, controls the pH at the epithelial cell surface. It has been reported that CF-affected epithelia, particularly in the gastrointestinal tract, secrete fluid with a more acidic pH than normal epithelia (11,12). Whether this is also true for airway surface liquid is still controversial (13,14), but recent measurements of the pH and HCO 3 Ϫ concentration of fluid secreted by polarized human submucosal gland cells, Calu-3, indicate that these cells are capable of secreting substantial amounts of HCO 3 Ϫ (ϳ80 mM) under appropriate stimulation, a process that would be defective in CF (15). An acidic luminal environment affects the physical properties of mucus (16,17) and promotes bacterial binding to mucins (18,19), both of which may have important implications for CF lung disease (20). As many CF-affected epithelia normally secrete substantial amounts of HCO 3 Ϫ , the luminal HCO 3 Ϫ concentration will vary under different physiological situations. This is particularly the case for the pancreas, a tissue in which CFTR is highly expressed and is severely affected in CF. Although plasma HCO 3 Ϫ is ϳ25 mM, the concentration of HCO 3 Ϫ in pancreatic juice can reach ϳ140 mM in humans, and because pancreatic juice is isotonic with plasma, these high HCO 3 Ϫ concentrations are accompanied by a reciprocal fall in juice Cl Ϫ concentration (21, 22). Thus under physiological conditions, the apical surface of pancreatic duct cells and therefore the extracellular face of CFTR will be exposed to large variations in external Cl Ϫ (Cl o Ϫ ) and HCO 3 Ϫ (HCO 3 o Ϫ ) concentrations. A similar but less extreme situation is also lik...