Maleic acid rate constant

A large number of 7i-complexes of Cu(I) are known. Recently a detailed study of the kinetics of formation (123) and the stability constants of copper(I) complexes with the three acid-base forms of fumaric and maleic acid were carried out (153). The results demonstrate that the rate constants of the reaction... 

Before the first muonic radicals were observed in 1978 by Roduner et al. (122), rate constants had been measured for the addition of Mu to unsaturated compounds in aqueous solution (Table XI). If k Jku is larger than 3, tunneling may be important, since otherwise differences in the vibrational zero-point energy in the transition state can decrease this ratio (128). In the case of maleic acid, the Arrhenius parameters were determined as A = (2.3 0.2) x 1013 AT-1 sec-1 and E = 18.8 1.7 kJ mol-1. Rate constants were also measured for addition to the CN triple bond (127). 

In addition to the above-listed systems, a minimum of the rate constant was observed for the Zn(II)/Zn(Hg) systems in water-methanol [232] and for the Mn(II)/Mn(Hg) systems in water-acetonitrile mixtures [230]. Electroreduction of T1(I), Zn(II) and maleic acid was also studied in water-acetone [273] and water-ethanol [274] mixtures. 

Sulfopropionic and sulfosuccinic acids were synthesized by addition of bisulfite to unsaturated acids. At pH 5, 55°C, and 0.5 N ionic strength, the second-order rate constants and activation energies for sulfonation of acrylic, fumaric, and maleic acids were, respectively ... 

The rate constants do not vary significantly from pH 3.5 to 7.0, but no reaction occurs at pH 2 or 13. The sulfonation rates increase with ionic strength. With fumaric and maleic acids, there may also be an additional catalytic effect of Mg" " or Ca"1-1". 

Below, we describe crystal-detector electrode shielding experiments for both the dissolution process alone and in the presence of polymaleic acid. Homo- and co-polymers of maleic acid are well-documented precipitation inhibitors [249-251]. Firstly, however, we consider the theoretical relationship between the shielding current and the heterogeneous rate constant for the reaction of H+ with the crystal surface. 

The data of acrylamide (AAm) and maleic acid show that there is little isotope effect. As these rate constants are near the diffusion controUed limit of 2x 10 M s", it indicates that the diffusion of small particles like H and Mu may be controlled by the radius and not by the mass. 

From the ratio of polyampholyte and metal ion concentrations at which a maximum reaction rate is observed one can ascertain the composition of catalytically active complexes [82]. The effect of [polyampholyte]/[metal ion] composition on Vq at a constant metal ion concentration for several polyampholyte-metal systems is illustrated in Fig. 7. For a majority of the systems the ratio is not higher than 3. These results support the contention that catalytic activity ctm occur only in the presence of free sites in the coordination sphere of a metal ion [83]. An exception to this is the styrene-A/ N-dimethylaminopropylmonoamide of maleic acid/copper(II) complex for which a maximum rate of H2O2 decomposition was found at [polyampholyte]/ [Cu ] = 16 1 and pH = 8.5. Because the isoelectric state of the polyampholyte is attained at pH 6.4 it is unlikely that the compression of the macromolecule coil has affected the complex composition. Apparently it is the presence of hydrophobic styrene units in the copolymer that affects the reaction rate. 

It is interesting that Kirby and his co-workers have shown that alkyl substituents have a very large rate enhancing effect on the formation of maleic anhydride from N-alkyl maleamic acids and that Eberson and Welinder have shown that they have a large effect on the equilibrium constant for the formation of maleic anhydride from maleic acid. In these compounds there is no question of a change in the rotamer population, and the effect must arise from a relief of nonbonding interactions on cyclization. 

The reaction should be carried out adiabatically in a semibatch reactor, feeding hexanol into the liquid maleic acid. The reactor volume is 500 dm, and no solvent is used. Maleic acid melts at 53°C. A maximum temperature of 100°C may not be exceeded due to the formation of by-products. The reaction is of second order, and the rate constant is expressed as... 

Where ri and r2 represent forward and backward reaction rates for step-I respectively and r3, r4 for step-II and Ci to C5 are concentrations (kmol/m ) of Maleic acid. Methanol, and Mono-methyl maleate, Di-methyl maleate and water respectively. The rate constants ki to k4 for the homogeneous reaction were evaluated by the same procedure described earlier in Chapter 2. The overall reaction rate was represented as ... 

A similar behavior is observed from competitive dissociations of protonated monoamides of maleic and fumaric acids which lead to the formation of [MH H2O] and [MH NH3] +, respectively. They are accompanied by the presence of NH, although the loss of water corresponds to the base peak from the Z stereochemistry but is of lower abundance from the E isomer. From fumarate monomethyl ester or monoamide, the major pathway for protonated molecule dissociation corresponds to the loss of XH as methanol or ammonia, respectively, which suggests that the modified carboxylic group is the preferred protonation site (Scheme 17.8). Consequently, the favorable loss of water from the Z isomers (not only for maleic acid, but also for the monoester and monoamide derivatives) indicates that the water loss rate constant, via 1,6-H" transfer, is much larger than that occurring from the E isomer which involves either 1,3-H" transfer (a symmetry forbidden process) or a multistep proton migration which is characterized by higher transition state level(s) (Scheme 17.8). 

The oxidation of substituted /3-benzoylpropionic acids by PFC follows the Hammett relation with a negative reaction constant. A possible mechanism for the oxidation has been discussed.5 The oxidation of maleic, fumaric, crotonic, and cinnamic acids by PCC is of first order with respect to PCC and the acid. The oxidation rate in 19 organic solvents has been analysed by Kamlet s and Swain s multiparametric equations. A mechanism involving a three-centre transition state has been postulated.6 The relative reactivity of bishomoallylic tertiary alcohols toward PCC, to yield substituted THF products via the tethered chromate ester, is dependent only on the number of alkyl groups. This observation suggests a symmetrical transition state in this intramolecular Cr(VI)-alkene reaction.7 Mechanisms have been proposed for the oxidation of 2-nitrobenzaldehyde with PBC8 and of crotonaldehyde with tetraethylammonium chlorochromate.9... 

A new class of acyclic nitroxides was more recently reported (N10-N14 in Figure 5.6) (Benoit et al, 1999, 2000 Grimaldi et al, 2000 Jousset 8c Catala, 2000 Catala et al, 2001 Drockenmuller 8c Catala, 2002). First, because of a larger activation-deactivation equilibrium constant, faster rates of polymerisation than with TEMPO were observed for styrene polymerisation. In addition, these nitroxides were shown to be well suited for the living polymerisation of several other monomers including acrylates, acrylamides, acrylic acid, acrylonitrile, maleic anhydride and isoprene (Hawker et al, 2001 Hawker, 2002). 

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