Sulphonation of Benzene

Atom Economy

The atom economy of a reaction is found from:

atom economy = molecular mass of desired products / molecular mass of all reactants x 100%

The atom economy works out to be 36.7%, which is not very good! This means that considerably less than half the mass of reactants ends up in the required product, even if we assume 100% yield. In practice the yield is more likely to be in the region of 88%, giving a figure of 32.3%, barely a third of the reactant mass.

Sodium sulphite has uses in the wood pulp and paper industry, and in several other processes, but the large amount of waste produced is one of the reasons why the benzene sulphonation route is no longer used.

Although this process is no longer in common use, some understanding of it will make the benefits of newer processes more obvious. The process involves several steps, but the overall reaction is:


How would the atom economy be calculated for this method of production, assuming the sodium sulphite and water are waste, and the process gives 100% yield?




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