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Rhodium catalysts supported on ZrO 2 , carbon, a cross-linked polystyrene with pendant Ph 2 P groups (SDT) or polyvinylpyrrolidone have been tested as catalysts for the heterogeneous carbonylation of methanol in the bulk liquid phase. In all cases, leaching of the catalyst into solution occurs and the observed increase in the rate of production of methyl ethanoate with time is attributed to the rate of the homogeneous reaction being faster than that of the heterogeneous. A detailed kinetic analysis for the catalyst supported on polyvinylpyrrolidone suggests that the rate constant for the homogeneous reaction is ca. 2× that of the heterogeneous at 150°C.

Summary The effect of toxin concentration on the kinetics of haemolysis of rabbit erythrocytes has been studied at pH values differing by about 0·5 pH units over the range 5·5 to 8·5 for both crude and partially purified toxin at concentrations of 2·5, 5·0, 10, 20, 30, 40, 60 MHD per ml and at 80 and 120 MHD per ml for the partially purified toxin. Increased concentration of toxin caused a decrease in the prelytic lag time (·) of the sigmoid haemolysis curves, a decrease in the time to reach 50 per cent. haemolysis (t1/2), and an increase in the maximum rate of haemolysis (Rm). Plateaux in Rm-toxin concentration, ·-toxin concentration and t1/2-toxin concentration curves were found at all pH values: these were displaced to higher concentrations in plots drawn for the partially purified toxin. The effect of pH on haemolysis is very marked, and pH profiles for the maximum rate of haemolysis were constructed: for the crude toxin, the shape of the profile changed as the toxin concentration was increased, while for the partially purified toxin the shape was independent of toxin concentration. The pattern of the profiles indicates that the crude toxin contains a small concentration of impurity that is strongly lytic at pH 5·5 and less markedly so at 8·5; the impurity has no significant effect at intermediate pH values. The reaction is first order with respect to toxin over a very small range of concentrations only, and the maximum rate of haemolysis is independent of toxin concentration at concentrations greater than 120 MHD per ml. The reaction is first order with respect to erythrocytes at all pH values, and over all measurable concentrations.

The kinetics of the acid hydrolysis of glycine ethyl ester, β-alanine ethyl ester, methylbetaine methyl ester, and acetylcholine have been studied over a range of temperatures by use of a conventional titration technique. The effect of ionic strength has also been studied. The Arrhenius parameters for the reactions have been found. The electrostatic effects of the positively charged centres in the ester molecules have been discussed.

1. Certain aromatic polysulphonic acids, previously tested for inhibition of the haemolytic activity of staphylococcal alpha-toxin, together with some additional related compounds, were tested as possible inhibitors of alpha-toxin in mice. 2. Compounds that inhibited the haemolytic activity of alpha-toxin at concentrations of 0.16mm or less [compounds (I), (II), (IV), (V), (VII) and (VIII)] were found to inhibit the lethal effect of alpha-toxin. 3. With the exception of compound (VIII), amounts of 1mg. were required to inhibit 4 LD(50) of toxin when the test compounds were premixed with alpha-toxin before injection; comparable inhibition with 0.3mg. of compound (VIII) was achieved without prolonged premixing. 4. Mixtures of alpha-toxin and compounds (I) and (II) containing an excess of test compound showed markedly diminished inhibitory activities. 5. The ;half-molecule' analogues of group 1 [compounds (III) and (XVIII)] were non-inhibitory. 6. Compounds (I)-(V), when administered separately from alpha-toxin by the same route (intraperitoneal), were active only when injected almost simultaneously with toxin, whereas compounds (VII) and (VIII) were strikingly inhibitory when injected 15min. before or after the toxin. 7. Compound (VIII) failed to inhibit the lethal effect of alpha-toxin when injected by a different route (intravenous).

1. The effect of a number of aromatic polysulphonic acids on the kinetics of haemolysis of rabbit erythrocyte suspensions by crude staphylococcal alpha-toxin was studied at pH8.6 and 6.8. 2. All of the inhibitory compounds caused an increase in the prelytic lag time (tau) of the sigmoid haemolysis curves, an increase in the time to reach 50% haemolysis (t((1/2))) and a decrease in the maximum rate of haemolysis (R(max.)). The most inhibitory compounds caused a 50% decrease in R(max.) at concentrations between 0.1 and 0.2mm. 3. The effect of pH varied considerably: compounds (I) and (II) were almost equally inhibitory at both pH values, compounds (IV) and (IX) were more inhibitory at pH6.8 than at pH8.6, and compounds (VII), (VIII), (X), (XI) and (XII) were more inhibitory at pH8.6. 4. Increased time of premixing alpha-toxin with compound (I) caused increased inhibition. 5. An attempt was made, where possible, to relate the inhibitory activity to the structure of the test compound.

The kinetics of the alkaline hydrolysis of acetylcholine have been studied using a pH-drop method at 25, 35·5, and 50°, and using a conventional titration technique at 0°. At 25, 35·5, and 50° the hydrolysis was studied over a range of ionic strength. The rate constants and energy and entropy of activation all show the expected dependence on ionic strengths. The effect of charge on rate is discussed with reference to the rate constant and the Arrhenius parameters. From a detailed comparison with the enzymic hydrolysis by acetylcholine esterase, in terms of the available data for the various steps in the reaction sequence postulated for the enzymic reaction, certain trends are noted.

Data for many non-aqueous solvents appear to demonstrate a correlation similar to that between enthalpies of hydration and ionisation energies.

The kinetics of the alkaline hydrolysis of methyl betaine methyl ester have been studied using a pH-stat in aqueous solution, over a range of hydroxide ion concentrations at 0, 25, and 42°, and at an ionic strength of 0·1M. The results show the presence of a very small but detectable water rate at 25 and 42° but not at 0°. The effect of ionic strength has been studied. Rate constants and the energy and entropy of activation all show the expected dependence on ionic strength. Methyl betaine methyl ester has been shown to hydrolyse approximately three times faster at 25° than ethyl betaine ethyl ester. The Arrhenius parameters for both reactions are discussed. A comparison of ethyl betaine ethyl ester with glycine ethyl ester shows the effect of introducing both charge and substituent, while a comparison with the reaction of the protonated glycine ethyl ester shows the effect of substitution only. Such comparisons indicate that, though the introduction of a charge on the N atom has a major effect on the rate, substitution at this centre has little effect. This is also discussed with reference to the Arrhenius parameters for the relevant reactions.

The kinetics of the alkaline hydrolysis of glycine ethyl ester have been studied in aqueous solution over a wide range of pH at 0, 25, 35·5, 41·95, and 49·45°. Corrections have been made to account for protonation of the reactant ester and the product, glycine. The effect of ionic strength on the reaction rate is discussed. The results are consistent with a reaction scheme which involves two simultaneous second-order reactions of hydroxide ion with the non-protonated and protonated forms of the ester. Rate constants describing these two reactions have been found from the composite observed rate constant at all temperatures, and corresponding Arrhenius parameters are reported. Surprisingly, the reaction of the protonated ester seems to have the lower activation energy. The equilibrium constant for the ionisation of the ester as an acid has been studied as a function of ionic strength, and of temperature. Values of ΔG°, ΔH°, and ΔS° for this ionisation are reported.