THIS DISCLOSURE CONCERNS THE REPARATION OF A HYDROCARBON COMPOSITION CONTAINING A MAJOR AMOUNT OF ALKYL AROMATIC COMPOUNDS HAVING TWO LONG-CHAIN ALKYL GROUPS AND A MINOR AMOUNT OF ALKYL-SUBSTITUTED TETRAHYDRONAPHTHALENES BY THE DISPORTIONATION OF AROMATIC COMPOUNDS HAVING ONE LONG-CHAIN ALKYL GROUP USING ALUMINUM CHLORIDE OR ALUMINUM BROMIDE AS THE CATALYST. THE TERM "LONG-CHAIN REFERS TO LINEAR ALKYL GROUPS CONTAINING FROM ABOUT 8 TO ABOUT 18, PREFERABLY FROM ABOUT 10 TO ABOUT 16, CARBON ATOMS. THE HYDROCARBON COMPOSITION (I.E. DISPROPORTIONATED PRODUCT) IS USEFUL AS A SULFONATION FEEDSTOCK AND AS A LUBRICANT.