Maleic anhydride, viii

Table VIII summarizes the cycloaddition reactions of azomethine ylides with maleimides and maleic anhydrides. The upper part of the table involves endo-selective cycloadditions and the lower part nonselective reactions. Endo selectivity is closely related to the substitution pattern of the azomethine ylides used. The azomethine ylides that show high endo selectivity to these cyclic olefins bear an ylide-stabilizing substituent of the carbonyl or cyano type (EWG) at one carbon and an aryl, heteroaryl, acyl, or 1-alkenyl substituent (R ) at the other. These key substituents must be present for high endo selectivity, although the substituent (R) on the ylide nitrogen is equally important.

The presence of stabilizer has little effect on poly (vinyl chloride) carboxylation (Table VIII). Since the other polymers were also subjected to the carboxylation process without removing commercial additives such as antioxidants, UV and thermal stabilizers, antiblocking agents, etc.—the additives inhibit neither the polymerization of the styrene-maleic anhydride complex nor the grafting reaction. 

The hydrophobization of cellulose surface was often achieved thanks to the well-known aptitude of cellulose macromolecules to undergo esterification reactions. The main coupling agents used to esterify cellulose using nonswelling solvents, in order to limit the reaction to the fibre s surface, are summarized in Scheme 18.1, namely the classical acetic anhydride [24] (I), alkyl ketene dimer (AKD) II, alkenyl succinic anhydride (ASA) III, fatty acids (IV, with n var5fing from 6 to 22) or their chlorides, poly-(propylene-gra/f-maleic anhydride) (V), trifluoroethoxy-acetic acid (VI) and its anhydride, as well as several other perfluoro-derivatives, p5Tomellitic anhydride (VII), styrene-maleic anhydride copolymer (VIII) and methacrylic anhydride (IX). 

Modifying components other than phthalic anhydride are frequently used in the preparation of unsaturated polyesters in order to impart special properties to the final product. Adipic and sebacic acids are employed to give flexible materials and isophthalic acid (VI) is used for tough products with higher heat distortion temperatures. The use of e (iomethylenetetrahydrophthalic anhydride ( nadic anhydride ) (VII), the Diels-Alder reaction product of cyclopentadiene and maleic anhydride, leads to a substantial improvement in heat resistance. Flame resistant materials are obtained by the use of chlorinated acids and anhydrides, e.g., tetrachlorophthalic anhydride (VIII) and chlorendic acid (HET acid) (IX). The latter is prepared by the Diels-Alder reaction of hexachlorocyclopentadiene and maleic anhydride the initial product is chlorendic anhydride but this rapidly absorbs water from the air to give the acid. 

In this study a number of dibasic acids or their anhydrides were used. Results obtained using succinic anhydride and maleic acid, summarized in Table VIII, are particularly pertinent. When... 

The cobalt chelate 2 4 1 reacted with maleic or phthalic anhydride selectively giving resp. 72 and 85 hlole % of monoesters as seen in Table VIII.In contrast the disodium alcoholate gave up to 65% of monoesters. No selectivity was obtained with succinic anhydride. 

Table VIII. Composition of esterification products of sucrose chelates and alcoholates with maleic and phtha-lic anhydride in DMF, 3 h, 60°C, mole-%.

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