is manufactured in the classical sulfonate fusion process only by Koppers (now Indspec), the sole US producer. Hoechst, previously the only manufacturer in Western Europe, ceased production early in 1992. The starting material is benzene, which is sulfonated in two steps using an older method. The monosulfonic acid is produced with 100% H₂SO₄ at about 100 °C and then converted to m-disulfonic acid with 65% oleum at 80-85 °C. In a separate continuous Hoechst process, benzene and SO₃ are reacted in a m-benzenedisulfonic acid melt at 140-160°C. The melt is neutralized directly. This shortens the older resorcinol route by one step; in addition, the disodium salt of the resorcinol contains very little Na₂SO₄.

The reaction of m-benzenedisulfonate to resorcinol takes place in an alkaline melt at about 300°C:

Resorcinol is obtained from its disodium salt after neutralizing the excess NaOH in the aqueous solution of the melt. In addition to the Na₂SO₃ from the actual reaction, Na₂SO₄ is formed by acidification with H₂SO₄. The crude resorcinol is extracted from the acidified aqueous solution with and purified by vacuum distillation. The selectivity can be as high as 82% (based on C₆H₆).

The unfavorable economic and ecological aspects of this classical resorcinol manufacture have prompted several firms to attempt to transfer the Hock phenol synthesis to resorcinol. In this analogy, rn-diisopropylbenzene would be oxidized to dihydro-peroxide and then convcrtcd, by acidic cleavage, into acetone and resorcinol:

It was found that the two hydropcroxide groups in the molecule give rise to a much greater number of byproducts from parallel and secondary reactions than with cumcnc hydroperoxide. In addition, the rate of reaction is considerably lower, so that only low space-time yields can be attained.