Tetrahydrophthalic anhydride, cis-

DescriptionTetrahydrophthalic anhydride is an organic compound with the formula C6H8C2O3. The compound exists as two isomers, this article being focused on the more common cis isomer. It is a precursor to other compounds including the dicarboxylic acid tetrahydrophthalic acid as well the tetrahydrophthalimide, which is a precursor to the fungicide Captan. It is a white solid that is soluble in organic solvents.Tetrahydrophthalic anhydride, the cis isomer, is prepared by the Diels-Alder reaction of butadiene and maleic anhydride.

UsesTetrahydrophthalic Anhydride is an anhydride hardener mainly used in the fields of coatings, epoxy resin curing agents, polyester resins, adhesives, plasticizers, pesticides, etc. It is also used as a chemical intermediate for light colored alkyds.Tetrahydrophthalic Anhydride is an organic compound obtained from the reaction of Maleic Anhydride and Butadiene.

Usescis-1,2,3,6-Tetrahydrophthalic anhydride (THPA) can be used as: A curing agent for epoxides. A chemical modifier in the modification of polystyrene via Friedel-Crafts acylation for enhancing the thermal stability of the polymer. A reactant for the synthesis of cis-tetrahydroisoindole-1,3-dione derivatives and cyclic diimides.

PreparationA flask containing 500 ml of dry benzene and 196 gm (2 moles) of maleic anhydride is heated with a pan of hot water while butadiene is introduced rapidly (0.6-0.8 liter/min) from a commercial cylinder. The solution is stirred rapidly and the heating is stopped after 3-5 min when the temperature reaches 50°C. In 15-25 min the reaction causes the temperature of the solution to reach 70-75°C. The absorption of the rapid stream of butadiene is nearly complete in 30-40 min. The addition of butadiene is continued at a slower rate for a total of 2\ hr. The solution is poured into a 1-liter beaker which is covered and kept at 0-5°C overnight. The product is collected on a large Buchner funnel and washed with 250 ml of b.p. 35-60°C petroleum ether. A second crop is obtained by diluting the filtrate with an additional 250 ml of petroleum ether. Both crops are dried to constant weight in an oven at 70-80°C to yield 281.5-294.5 gm (96- 97%, m.p. 99-102°C). Recrystallization from ligroin or ether raises the melting point to 103-104°C.