Sulfonation reaction kinetics

This water, due to the dilution effect on the still unreacted sulfuric acid, causes the progressive loss of the latter s reactivity. This loss implies the necessity of continuous removal of the formed water or operating the process with excess of the sulfonating agent and eventually to separate, by physical settling, the weak-spent sulfuric acid that is not capable to comply with the desired sulfonation reaction kinetics anymore. 

Schmid et al. studied in detail the sulfonation reaction of fatty acid methyl esters with sulfur trioxide [37]. They measured the time dependency of the products formed during ester sulfonation. These measurements together with a mass balance confirmed the existence of an intermediate with two S03 groups in the molecule. To decide the way in which the intermediate is formed the measured time dependency of the products was compared with the complex kinetics of different mechanisms. Only the following two-step mechanism allowed a calculation of the measured data with a variation of the velocity constants in the kinetic differential equations. 

Rhin(bpy)3]3+ and its derivatives are able to reduce selectively NAD+ to 1,4-NADH in aqueous buffer.48-50 It is likely that a rhodium-hydride intermediate, e.g., [Rhni(bpy)2(H20)(H)]2+, acts as a hydride transfer agent in this catalytic process. This system has been coupled internally to the enzymatic reduction of carbonyl compounds using an alcohol dehydrogenase (HLADH) as an NADH-dependent enzyme (Scheme 4). The [Rhin(bpy)3]3+ derivative containing 2,2 -bipyridine-5-sulfonic acid as ligand gave the best results in terms of turnover number (46 turnovers for the metal catalyst, 101 for the cofactor), but was handicapped by slow reaction kinetics, with a maximum of five turnovers per day.50... 

Most carbocations are too reactive to be directly observable in ordinary solvents, and until relatively recently evidence has been obtained indirectly, primarily through the study of reaction kinetics and trapping processes, experiments discussed in Sections 5.1, 5.2, and 5.4. Nevertheless, a few types of compounds have long been known to produce observable concentrations of positive ions relatively easily. The triarylmethyl derivatives were the first of this type to be investigated the halides ionize readily in non-nucleophilic solvents such as sulfur dioxide,70 and the alcohols yield solutions of the ions in concentrated sulfuric acid. Early observations by the freezing-point depression technique (see Section 3.2, p. 130) established that each mole of triphenyl carbinol yields 4 moles of ions in sulfuric acid, the reaction presumably being by way of Equation 5.14.71 Results in methane-sulfonic acid are similar.72... 

Oh et al. [16] have demonstrated that a microemulsion based on a nonionic surfactant is an efficient reaction system for the synthesis of decyl sulfonate from decyl bromide and sodium sulfite (Scheme 1 of Fig. 2). Whereas at room temperature almost no reaction occurred in a two-phase system without surfactant added, the reaction proceeded smoothly in a micro emulsion. A range of microemulsions was tested with the oil-to-water ratio varying between 9 1 and 1 1 and with approximately constant surfactant concentration. NMR self-diffusion measurements showed that the 9 1 ratio gave a water-in-oil microemulsion and the 1 1 ratio a bicontinuous structure. No substantial difference in reaction rate could be seen between the different types of micro emulsions, indicating that the curvature of the oil-water interface was not decisive for the reaction kinetics. More recent studies on the kinetics of hydrolysis reactions in different types of microemulsions showed a considerable dependence of the reaction rate on the oil-water curvature of the micro emulsion, however [17]. This was interpreted as being due to differences in hydrolysis mechanisms for different types of microemulsions. 

Multiple scan DSC curves at various heating rates were utilized to obtain kinetic parameters for an acetylene terminated sulfone (ATS) which were compared with isothermal reaction rates. The comparison between scanning and isothermal reaction kinetics illustrated the retarding effect of incipient vitrification of the ATS on the reaction rate. 

Electrolytes are a critical material in the performance of electrolyzers. Low-temperature electrolysis of water relies on proton exchange membrane (PEM) cells using sulfonated polymers for the electrolytes. Key issues for all electrolyzers are the kinetics of the system that is controlled by reaction and diffusion rates. Catalysts such as platinum, Ir02, and RUO2 are used to improve the reaction kinetics, but they also contribute to the cost of the system, which is also an issue. Steam electrolysis is also a possibility at a temperature of about 1,000°C using ceramic membranes. 

From a theoretical point of view this is an extremely interesting reaction. The displacement of a hydroxyl group from a saturated carbon atom appears to be unknown in basic solution. The fact that amino-methane sulfonic acid can be isolated from the bisulfite addition product of formaldehyde on treatment with ammonia does not prove, of course, that a direct displacement, such as is indicated in XVI to XVII, actually occurred. Furthermore, it is quite clear that preliminary formation of an imine (XVIII) is not necessary for the reaction of aromatic amines with sodium bisulfite (steps XIX to XVIII to XVII, etc.). 1-Dimethyl-aminonaphthalene-4-sulfonic acid (XX) and l-aminonaphthalene-4-sulfonic acid (XIX) show similar reaction kinetics 16a when treated with sodium bisulfite, yet with the tertiary amine (XX) it is not possible to write an imino structure corresponding to XVIII. 

This paper reports measuremerts of reaction kinetics for sulfonation of maleic, fumaric, and acrylic acids by sulfite addition and for hydration of acrylic acid with catalysis by H2SO4 or cation exchange resin. The kinetics were measured by sampling of isothermal batch reactors. 

A modified synthetic route to 3-isopropyl-l//-2,l,3-benzothiadiazin-4(3//)-one 2,2-dioxide (215) (Bentazon) (Section 6.16.12) involving sulfonylation of the 2-aminobenzamide (213 R = R = H) at the amine function with 2-methylpyridine-sulfur trioxide complex, followed by cyclization of the resulting 2-methylpyridinium sulfonate salt (214) with hot phosphorus oxychloride has been patented (Scheme 26) <89CZP257059, 91CZP270529). The reaction kinetics, particularly the cyclization of the 2-methylpyridinium salt (214), have been subjected to a detailed investigation <89Mi 6i6-02>. 

Decrease of proton conductivity above 100 °C. Not only Nafion but also most of the sulfonated polymers tend to dehydrate at these temperatures. There are reasons to operate the fuel cell at 130°C or even higher temperatures the reaction kinetics would be improved and the contamination of the catalyst by CO and the problems with water drag in the membrane would be minimized. 

The continuous development of the process design focused on appropriate snifonation equipment that is necessary to transfer all the findings from the parallel laboratory studies on the L AB-SO3 reaction kinetics and mechanisms to an industrial scale. Although these efforts have been initiated from the beginning of the use of synthetic surfactants, new doubts concerning sulfonation chemistry... 

In 1993, Okamoto et al. studied the reactive pervaporation process for the production of ethyl oleate starling from oleic acid and ethanol. An ESU configuration was used together with a noncatalytic asymmetric PEF4,4-oxydiphenylene pyromelliti-mide and p-toluene sulfonic acid as catalyst. A model was set by the authors (coupling reaction kinetics with the pervaporafion permeate flux relation) to evaluate all critical parameters to tune PVMR parameters and obtain a conversion of 98%. 

Finally, to favor the commercial issue of DMFC, new low cost components have to be developed, including catalysts with a lower amount of PGM or even with no noble metal, and high-temperature-resistant membranes of lower cost than sulfonated perfiuorinated membrane (Nafion ) and of higher protonic conductivity and stability to operate the DMFC at higher temperatures (150-200 °C) which may increase the power density through thermal activation of the reaction kinetics. 

Since a perfluorosulfonic acid ionomer such as Nafion is normally used to make the catalyst layer, trifluoromethane sulfonic acid (CF3SO3H) is expected to behave more closely to the ionomer than the inorganic acids are. In addition, CF3SO3H and its anion (CF3SO3 ) do not adsorb onto the surface of the Pt catalyst and thus do not affect the reaction kinetics. 

Cross-linked polystyrene film was sulfonated by treatment with a mixture of chlorosulfonic acid and anhydrous sulfuric acid (8 92) at 0 °C. The kinetics of the sulfonation reactions were determined the initial rate was slow, reached a... 

When unsubstituted, C-5 reacts with electrophilic reagents. Thus phosphorus pentachloride chlorinates the ring (36, 235). A hydroxy group in the 2-position activates the ring towards this reaction. 4-Methylthiazole does not react with bromine in chloroform (201, 236), whereas under the same conditions the 2-hydroxy analog reacts (55. 237-239. 557). Activation of C-5 works also for sulfonation (201. 236), nitration (201. 236. 237), Friede 1-Crafts reactions (201, 236, 237, 240-242), and acylation (243). However, iodination fails (201. 236). and the Gatterman or Reimer-Tieman reactions yield only small amounts of 4-methyl-5-carboxy-A-4-thiazoline-2-one. Recent kinetic investigations show that 2-thiazolones are nitrated via a free base mechanism. A 2-oxo substituent increases the rate of nitration at the 5-position by a factor of 9 log... 

The azo coupling reaction proceeds by the electrophilic aromatic substitution mechanism. In the case of 4-chlorobenzenediazonium compound with l-naphthol-4-sulfonic acid [84-87-7] the reaction is not base-catalyzed, but that with l-naphthol-3-sulfonic acid and 2-naphthol-8-sulfonic acid [92-40-0] is moderately and strongly base-catalyzed, respectively. The different rates of reaction agree with kinetic studies of hydrogen isotope effects in coupling components. The magnitude of the isotope effect increases with increased steric hindrance at the coupler reaction site. The addition of bases, even if pH is not changed, can affect the reaction rate. In polar aprotic media, reaction rate is different with alkyl-ammonium ions. Cationic, anionic, and nonionic surfactants can also influence the reaction rate (27). 

---