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Kinetics, maleic anhydride

Maleic anhydride has been used in many Diels-Alder reactions (29), and the kinetics of its reaction with isoprene have been taken as proof of the essentially transoid stmcture of isoprene monomer (30). The Diels-Alder reaction of isoprene with chloromaleic anhydride has been analy2ed using gas chromatography (31). Reactions with other reactive hydrocarbons have been studied, eg, the reaction with cyclopentadiene yields 2-isopropenylbicyclo[2.2.1]hept-5-ene (32). Isoprene may function both as diene and dienophile in Diels-Alder reactions to form dimers. [Pg.463]

Isomerization. Maleic acid is isomerized to fumaric acid by thermal treatment and a variety of catalytic species. Isomerization occurs above the 130 to 140°C melting point range for maleic acid but below 230°C, at which point fumaric acid is dehydrated to maleic anhydride. Derivatives of maleic acid can also be isomerized. Kinetic data are available for both the uncatalyzed (73) and thiourea catalyzed (74) isomerizations of the cis to trans diacids. These data suggest that neither carbonium ion nor succinate intermediates are involved in the isomerization. Rather, conjugate addition imparts sufficient single bond character to afford rotation about the central C—C bond of the diacid (75). [Pg.452]

The chemical modification of PS with epichlorohydrin (EC), maleic anhydride (MA), acetic anhydride (AA), butadiene, and isoprene in the presence of cationic catalysis such as AICI3, FeCU, BF3 0(C2H5)2, ZnCb, TiCL, and SnCU, have been extensively studied under various conditions for the last 15 years. We have also studied their kinetics, physico-mechanical, thermal, and dielec-... [Pg.263]

Show that the reaction follows first-order kinetics when [A]0 s> [S]o, and show that lAi > varies linearly with l/[A]. The same pattern is seen when maleic anhydride (B) is used instead of A, except that the line in the double reciprocal plot is parallel to the abscissa. It intersects the ordinate at the same point as the y-intercept for A. Why are the slopes for A and B different, and their intercepts the same ... [Pg.98]

Since anhydrides are much more reactive than carboxylic acids, reaction kinetics is controlled by the second step. The scope and apphcations of this reaction are the same as direct polyesterification but are practically limited to the synthesis of unsaturated polyesters and alkyd resins from phtliahc and maleic anhydrides (see Sections 2.4.2.1 and 2.4.23). [Pg.65]

The thermal reaction of cyclopentadiene (1) with maleic anhydride gives 98 % kinetically favoured endo adduct, unless the mixture is heated for a long time [44]. Under photolysis conditions and in the presence of triethylamine in dry ethanol, a reversed selectivity was found [45] (Scheme 4.13). [Pg.164]

PP is probably the most thoroughly investigated system in the nanocomposite field next to nylon [127-132]. In most of the cases isotactic/syndiotactic-PP-based nanocomposites have been prepared with various clays using maleic anhydride as the compatibilizer. Sometimes maleic anhydride-grafted PP has also been used [127]. Nanocomposites have shown dramatic improvement over the pristine polymer in mechanical, rheological, thermal, and barrier properties [132-138]. Crystallization [139,140], thermodynamic behavior, and kinetic study [141] have also been done. [Pg.46]

A Kinetic Study on the Solid State Grafting of Maleic Anhydride onto Isotactic Polypropylene in Supercritical CO2... [Pg.673]

Mechanistic studies have been designed to determine if the concerted cyclic TS provides a good representation of the reaction. A systematic study of all the E- and Z-decene isomers with maleic anhydride showed that the stereochemistry of the reaction could be accounted for by a concerted cyclic mechanism.19 The reaction is only moderately sensitive to electronic effects or solvent polarity. The p value for reaction of diethyl oxomalonate with a series of 1-arylcyclopentenes is —1.2, which would indicate that there is little charge development in the TS.20 The reaction shows a primary kinetic isotope effect indicative of C—H bond breaking in the rate-determining step.21 There is good agreement between measured isotope effects and those calculated on the basis of TS structure.22 These observations are consistent with a concerted process. [Pg.870]

Supemucleophilic polymers containing the 4-(pyrro-lidino)pyridine group were synthesized from the corresponding maleic anhydride copolymers and also by cyclopolymerization of N-4-pyridyl bis(methacryl-imide). The resulting polymers were examined for their kinetics of quaternization with benzyl chloride and hydrolysis of pj-nitrophenylacetate. In both instances, the polymer bound 4-(dialkylamino)pyridine was found to be a superior catalyst than the corresponding low molecular weight analog. [Pg.72]

Reactions of furan (5) under solvent-free conditions, catalyzed by Montmorillonite K10, have been described by Cintas [27]. The reaction with methyl vinyl ketone (32) produced Michael addition in positions 2 and 5, whereas reaction with symmetrically substituted cyclic dienophiles produced a mixture of the endo and exo adducts with the kinetically favored endo adduct predominating, except when maleic anhydride (39) was used as the dienophile (Scheme 9.2). [Pg.304]

Vaidyanathan and Doraiswamy (1968) studied the kinetics of the gas-phase partial oxidation of benzene (CgHg, B) to maleic anhydride (C4H2O3, M) with m in an integral PFR containing... [Pg.113]

The first examples of transition metal-catalyzed [5 + 2]-cycloadditions between vinylcyclopropanes (VCPs) and 7r-systems were reported in 1995 by Wender and co-workers.10 This [5 + 2]-reaction was based conceptually on the Diels-Alder reaction, replacing the four-carbon, four-7r-electron diene with a five-carbon, four-electron VCP (Scheme 1). Although the [5 + 2]-reaction of VCPs and 7r-systems can be thought of as a homolog of the Diels-Alder [4 +21-reaction, the kinetic stability of VCPs (activation barrier for the thermal isomerization of VCP to cyclopentene has been reported as 51.7 kcal mol-1)11 makes the thermal [5 + 2]-reactions involving VCPs and 7r-systems very difficult to achieve. A report of a thermal [5 + 2]-cycloaddition between maleic anhydride and a VCP has been published,12 but this reaction has not been reproduced by others.13 14 Based on the metal-catalyzed isomerization of VCPs to cyclopentenes and dienes,15-20 Wender and co-workers hypothesized that a metal might be used to convert a VCP to a metallocyclohexene which in turn might be trapped by a 7r-system to produce a [5 + 2]-cycloadduct. Based on its previous effectiveness in catalyzed [4 + 2]-21 and [4 + 4]-cycloadditions (Section 10.13.2.4), nickel(0) was initially selected to explore the potential of VCPs as four-electron, five-carbon components in [5 + 2]-cycloadditions. [Pg.605]

In addition, careful kinetic measurements and product analysis has revealed that the activation of the catalyst precursor 26b during the induction period occurs by hydrogenation of the coordinated maleic anhydride to succinic anhy-... [Pg.389]

The reactions of A-phenyl a-r-butyl nitrone (PEN) with maleimides, maleic anhydride, and diethyl maleate have been studied by EPR and two types of spin adduct detected. They arise from the reductive addition of PEN to the alkenes and the degradation product of DEN (2-methyl-2-nitropropane). The deuterium and muonium kinetic isotope effects for the addition of the hydrogen atom to a variety of alkenes have been determined experimentally and theoretically. ... [Pg.137]

The gas-phase selective oxidation of o-xylene to phthalic anhydride is performed industrially over vanadia-titania-based catalysts ("7-5). The process operates in the temperature range 620-670 K with 60-70 g/Nm of xylene in air and 0.15 to 0.6 sec. contact times. It allows near 80 % yield in phthalic anhydride. The main by-products are maleic anhydride, that is recovered with yields near 4 %, and carbon oxides. Minor by-products are o-tolualdehyde, o-toluic acid, phthalide, benzoic acid, toluene, benzene, citraconic anhydride. The kinetics and the mechanism of this reaction have been theobjectof a number of studies ( 2-7). Reaction schemes have been proposed for the selective pathways, but much less is known about by-product formation. [Pg.168]

An HRTEM study of Zn-Cr Fe oxides using surface-profiling methods in the EM has been reported by Briscoe et al (1984, 1985). Chemical kinetic studies of the oxidation of benzene to maleic anhydride over V-Mo-O catalysts (prepared using 3 V205 Mo03), have been described using GC-MS techniques (Lucas et al 1983). However, microstructural information is limited and there are opportunities for EM studies of these catalyst systems. [Pg.131]

Direct evidence about the first step of activation of butane was obtained on a V-P oxide catalyst in the butane oxidation to maleic anhydride based on deuterium kinetic isotope effect (34). It was found that when a butane molecule was labeled with deuterium at the second and third carbon, a deuterium kinetic isotope effect of 2 was observed. No kinetic isotope effect was observed, however, if the deuterium label was at the first or fourth carbon. By comparing the observed and theoretical kinetic isotope effects, it was concluded that the first step of butane activation on this catalyst was the cleavage of a secondary C—H bond, and this step was the rate-limiting step. [Pg.17]

The fact that the kinetic parameters are slightly dependent on conversion is probably due to inhibition by the product (maleic anhydride), as shown by the circulation flow experiments of Lyubarskii et al. [192], and represented by the negative order with respect to maleic anhydride in their power-rate equations. [Pg.199]

A V2Os—K2S04 catalyst was used in a kinetic study by Jaswal et al. [165] with a differential flow reactor at 350—400° C and varying benzene/ oxygen ratio. The overall benzene oxidation rate was adequately described by a simple redox model. Kinetic parameters are given in Table 29. The initial selectivity is not reported by the authors, but a value of 50—60% can be derived from the stoichiometric number n, assuming C02 and maleic anhydride as the main products. [Pg.199]

The kinetics of the p-xylene oxidation over tin vanadate was studied by Mathur and Viswanath [206], A differential reactor was used at 320— 380°C. p-Tolualdehyde, maleic anhydride and p-toluic acid are the main... [Pg.206]

Pant and Chanda [247] report a kinetic study with a sintered V2Os catalyst carried out with a spinning basket reactor. The following selec-tivities are observed at 450—517° C, independent of conversion (20— 40%) and temperature 80% phthalic anhydride, 10% maleic anhydride, 10% carbon oxides. The authors propose a parallel reaction scheme. However, these data, and the absence of tolualdehyde at this conversion level prove that the reactor did not function as a well-stirred reactor, but suffered considerable bypassing (mass transfer limitation with respect to... [Pg.213]

Aromatic hydrocarbons which have methyl side chains mainly behave like toluene and form aldehydes, while combustion is stimulated and selective oxidation of the nucleus is repressed. The oxidation of methyl-naphthalene, for example, exhibits a low selectivity with respect to phtha-lic anhydride formation, combustion and maleic acid formation being the dominating reactions. Durene is a special case because it resembles o-xy-lene. The oxidation of durene over a V—W—O catalyst at 420° C is reported to produce pyromellitic dianhydride, phthalic and maleic anhydride, although combustion dominates (Geiman et al. [122]). 1,2,4-Trimethyl-benzene yields dimethylbenzene and trimellitic acid if oxidized on a Sn— V—O catalyst. Kinetic data have been measured by Balsubramanian and Viswanath [37]. [Pg.220]

In many binary copolymerizations, there is a pronounced tendency for the two types of monomer unit to alternate along the copolymer chain. In extreme cases, there is almost perfect alteration, notably for pairs of monomers, e.g, maleic anhydride and stilbene, which do not polymerize on their own. Ternary copolymenzations are of practical importance die kinetic treatments developed for binary copolymerizations can be extended to diese systems. [Pg.1344]


See other pages where Kinetics, maleic anhydride is mentioned: [Pg.466]    [Pg.64]    [Pg.7]    [Pg.23]    [Pg.230]    [Pg.673]    [Pg.826]    [Pg.23]    [Pg.76]    [Pg.389]    [Pg.59]    [Pg.32]    [Pg.167]    [Pg.548]    [Pg.57]    [Pg.190]    [Pg.528]    [Pg.185]    [Pg.200]    [Pg.201]    [Pg.328]    [Pg.47]    [Pg.64]    [Pg.26]   


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Maleic anhydride

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