Maleio anhydride

Commercially, maleio anhydride is prepared more cheaply by the catalytic vapour phase oxidation (in the presence of vanadium pentoxide at about 400°) of benzene with atmospheric oxygen ... 

Both acids yield succinic acid, m.p. 185°, upon catalytic reduction (see Section 111,150), thus establishing their structures. Maleio and fumaric acids are examples of compounds exhibiting eU-trans isomerism (or geometric Isomerism). Maleic aoid has the cis structure since inter alia it readily yields the anhydride (compare Section 111,93). Fumaric acid possesses the trans structure it does not form an anhydride, but when heated to a high temperature gives maleio anhydride. 

A. Maleic acid. Assemble the apparatus shown in Pig. Ill, 28,. Place 45 g. of dry malic acid in the 200-260 ml. distilling flask and cautiously add 63 g. (57 ml.) of pure acetyl chloride. Warm the flask gently on a water bath to start the reaction, which then proceeds exothermically. Hydrogen chloride is evolved and the malic acid passes into solution. When the evolution of gas subsides, heat the flask on a water bath for 1-2 hours. Rearrange the apparatus and distil. A fraction of low boiling point passes over first and the temperature rises rapidly to 190° at this point run out the water from the condenser. Continue the distillation and collect the maleio anhydride at 195-200°. Recrystallise the crude maleic anhydride from chloroform (compare Section 111,93) 22 g. of pure maleic anhydride, m.p. 54°, are obtained. 

Poly (isobutene)/maleio anhydride adduot, diethanolamine reaotion prod, surfactant, polyacrylic fiber dyeing... 

To obtain maleio acid, evaporate the maleic anhydride with one half of its weight of water on a water bath remove the last traces of water by leaving in a desiccator over concentrated sulphuric acid. The resulting maleic acid has m.p. 143° and is quite pure (1). It may be recrystallised, if desired, from acetone - light petroleum (b.p. 60-80°) and then melts at 144° (1). 

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