This shows the synthesis of 4-Cyclohexene-cis-1,2-dicarboxylic anhydride (3) fro

Question

This shows the synthesis of 4-Cyclohexene-cis-1,2-dicarboxylic anhydride (3) from 1,4 addition of Maleic anhydride (2) to 1,3-butadiene(1). Note that the other functional groups on Maleic anhydride do not participate in the reaction but are left unchanged. Because the reaction of 1,4 addition occurs by a concerted mechanism, the product is the cis version. 1,3-Butadiene is a gas and thus needs to be handled under pressure. An easier way to use the reactant is to make it in situ. We will thermally decompose 3-sulfolene (4) to 1,3- butadiene (1) and sulfur dioxide.Write the balanced chemical reaction equation for this experimental synthesis (above). Calculate the molar mass of the reactants and product.

Important chemical amounts for equation and mass: 2.5 g of 3-sulfolene, 1.5 g of Maleic anhydride, 10 ml Xylene, about 10 ml petroleum ether, ice, water, 2 mL of 95% ethanol, two drops of 1% aqueous potassium permanganate solution.

Thank you! Please explain how you did the balanced equation.

Explanation / Answer

The calculations are as shown below,

The decomposiiton reaction of 1 mole sulfolene (4) at high temperature gives one mole of 1,3-butadiene (1) and 1 mole of sulfur dioxide.

The 4+2 cycloaddition reaction of 1 mole of 1,3-butadiene (1) with 1 mole of maleic anhydride (2) results in formation of 1 mole of 4-Cyclohexene-cis-1,2-dicarboxylic anhydride (3).

So the balalnced equation for all will be,

4 (molar mass 118.15 g/mol) ------> 1 (molar mass 54.0916 g/mol) + SO2 ( (molar mass 64.066 g/mol)

1 + 2 (molar mass 98.06 g/mol) -------------> 3 (molar mass 152.1516 g/mol)

Now, when we start with 2.5 g of sulfolene (4) we would get = 2.5 x 54.0916 / 118.15 g of (1)                

                                                                                                = 1.145 g of (1)

We take, 1/1.38(1.145g) of (1) and react with 1.5 g (2) to form 2.33 g of (3).  

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