A PROCESS IS PROVIDED FOR MAKING 2,4-DI-NITRO-6-SECALKYLPHENOLS USING BOTH 2,6-DI-SEC-ALKYLPHENOLS AND OSEC-ALKYLPHENOLS AS STARTING MATERIAL. IN THE FIRST STEP, 2,6DI-SEC-ALKYLPHENOLS ARE ADDED TO EXCESS CONCENTRATED SULFURIC ACID AT 75-150*C. CAUSING CONCURRENT DEALKYLATION AND SULFONATION. IN THE SECOND STEP, O-SEC-ALKYLPHENOLS ARE ADDED TO CONSUME MOST OF THE REMAINING SULFURIC ACID, PERMITTING REPLACEMENT OF SULFONIC ACID GROUPS WITH NITRO GROUPS BY REACTING THE FINAL MIXTURE WITH AQUEOUS ALKALI METAL NITRATES. THE PRODUCTS (E.G., 2,4-DI-NITRO-6-SEC-BUTYLPHENOL) ARE USEFUL AS SELECTIVE HERBICIDES.