Maleic anhydride reaction mechanism

The mechanism of the diene synthesis appears to involve an electron transfer from the diene to the dienophile, .e., it is initiated by an ionic reaction. The following scheme may represent the addition of 2 3-dimethylbutadiene to maleic anhydride ... 

Another class of reaction where you can see at once that the disconnection is the reverse of the reaction is Pericychc Reactions. An example would be the Diels-Alder reaction between butadiene and maleic anhydride. Draw the mechanism and the product. 

Compound 5 can be trapped through a Diels-Alder reaction with maleic anhydride and thus be shown to be an intermediate. Further evidence for a mechanism involving two subsequent allyl conversions has been provided by experiments with " C-labeled substrates. 

For example, the treatment of cellulose fibers with hot polypropylene-maleic anhydride (MAH-PP) copolymers provides covalent bonds across the interface [40]. The mechanism of reaction can be divided in two steps ... 

Maleic anhydride, 98 g (1.0 mol), 148 g (1.0 mol) of phthalic anhydride, and 160 g (2.1 mol) of 1,2-propanediol are poly condensed in a three-necked flask equipped with a mechanical stirrer, a nitrogen inlet, and a distillation head connected to a condenser and a receiver flask. The flask is placed in a salt bath preheated at 160°C. Water begins to distill and the temperature is then raised gradually to 190°C. The polycondensation is stopped (after about 15 h) when the reaction mixture has an acid number of 50 (see Section 2.3.8.4.1) (Scheme 2.54). A slightly different procedure is described in ref. 423. 

Luche and coworkers [34] investigated the mechanistic aspects of Diels-Alder reactions of anthracene with either 1,4-benzoquinone or maleic anhydride. The cycloaddition of anthracene with maleic anhydride in DCM is slow under US irradiation in the presence or absence of 5% tris (p-bromophenyl) aminium hexachloroantimonate (the classical Bauld monoelectronic oxidant, TBPA), whereas the Diels Alder reaction of 1,4-benzoquinone with anthracene in DCM under US irradiation at 80 °C is slow in the absence of 5 % TBPA but proceeds very quickly and with high yield at 25 °C in the presence of TBPA. This last cycloaddition is also strongly accelerated when carried out under stirring solely at 0°C with 1% FeCh. The US-promoted Diels Alder reaction in the presence of TBPA has been justified by hypothesizing a mechanism via radical-cation of diene, which is operative if the electronic affinity of dienophile is not too weak. 

The mechanism of cycloaddition reaction of maleic anhydride with anthracene promoted by US irradiation has been the subject of many controversies [32, 37]. Recent work of Da Cunha and Garrigues [35] shows that the reaction proceeds in toluene solution in the 60 85 °C temperature range in 6 3 h. 

The combination of Lewis-acid catalysis and sc-COi has also been investigated. One of these studies involved the AlCls-catalyzed Diels Alder reaction of isoprene and maleic anhydride in sc-COi at 67 °C and at 74.5-78.5 bar [89]. The reaction rate was enhanced with respect to the uncatalyzed reaction and an unconcerted two-step mechanism was suggested [89]. 

In another aspect of the mechanism, the effects of electron-donating and electron-withdrawing substituents (p. 1065) indicate that the diene is behaving as a nucleophile and the dienophile as an electrophile. However, this can be reversed. Perchlorocyclopentadiene reacts better with cyclopentene than with maleic anhydride and not at all with tetracyanoethylene, though the latter is normally the most reactive dienophile known. It is apparent, then, that this diene is the electrophile in its Diels-Alder reactions. Reactions of this type are said to proceed with inverse electron demand ... 

Under the present reaction conditions, we observed the formation of succinic anhydride almost simultaneously together with the formation of GBL. The hydrogaiation of maleic anhydride yields succinic anhydride, and the subsequent hydrogenation of succinic anhydride produces GBL. The rate of hydrogenation of maleic anhydride to succinic anhydride was very fast compare to that of succinic anhydride to GBL. When the reaction was CEuried out wifliout solvent, tetrahydrofiiran was not producal. The above results indicate that the Pd-Mo-Ni/SiOz catalyst under our experimental conditions played an important role for the selective formation of GBL. Therefore, it is inferred that the catalyst composition may influence the route by which tetrahydrofiiran was formed, probably due to the different absorption mechanism of maleic anhydride, succinic anhydride, and GBL. 

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. 

The thermal Diels-Alder reactions of anthracene with electron-poor olefinic acceptors such as tetracyanoethylene, maleic anhydride, maleimides, etc. have been studied extensively. It is noteworthy that these reactions are often accelerated in the presence of light. Since photoinduced [4 + 2] cycloadditions are symmetry-forbidden according to the Woodward-Hoffman rules, an electron-transfer mechanism has been suggested to reconcile experiment and theory.212 For example, photocycloaddition of anthracene to maleic anhydride and various maleimides occurs in high yield (> 90%) under conditions in which the thermal reaction is completely suppressed (equation 75). 

In the reaction of cyclopentadiene with maleic-D2 anhydride206 an inverse experimental KIE of 8% (KIE = 0.92) was found at 298 K. The reaction between butadiene-D4, D2C=CHCH=CD2 and maleic anhydride gave a large inverse D4-KIE of 0.76. The two reactions between anthracene and maleic anhydride presented below also favour the concerted rather than the stepwise mechanism which requires 3-6% KIE in the normal direction (i.e. >1). 

As an example of this technique we consider 12C/13C isotope effects in the Diels-Alder condensation of isoprene and maleic anhydride (Equation 7.32). The terminal carbons of isoprene carbons are numbered 1 and 4, the methyl substituted carbon is number 2. The reaction proceeds via a concerted and slightly asynchronous mechanism. 

Structurally similar photochromic maleic anhydride derivatives 177 with a similar reaction mechanism were prepared by Irie (05CL64) by a one-pot synthesis from 2-methoxybenzothiophene, oxalyl chloride, and pentene-3-carboxylic acid (3-pentenoic acid) in dichloromethane in the presence of triethylamine at 5°C for 2 h according to Scheme 54. 

Irradiation of o-methylbenzaldehyde in the presence of maleic anhydride give G. The same compound is obtained when H is heated with maleic anhydride. Both reactions give only the stereoisomer shown. Formulate a mechanism. 

Isopropenylbenzofuran (124, Scheme 30) affords good yields of the adducts 123 and 125 on separate reaction with maleic anhydride and tetracyanoethylene. With but-3-en-2-one, 2-isopropenylbenzofuran (124, Scheme 31) affords the adducts 126 and 127 in a combined yield of 29%. When the crude product was dehydrogenated with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in boiling benzene, the aromatized product 128 (6%) was obtained. It was accompanied by the dicyanodibenzofuran 129, which was found to arise from the excess diene present in the reaction mixture. A speculative mechanism is shown. 

Precise rate expressions are difficult to obtain because of the existence of reaction networks in which the secondary reactions take place with ease. Sometimes, the relative rate constants in a reaction network are reported and presented as the mechanism of a reaction. For example, butane > butene > furan - > 7 -butyllactone --> maleic anhydride. This is incorrect, as a different... 

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. 

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