C 2641 (OTTO) Cumene, 99%+ Cas no 98-82-8 used as the catalyst. C 2641 (OTTO) Cumene, 99%+ Cas no 98-82-8 - used as a thinner for paints, lacquers, and enamels and as a component of high octane fuels. C 2641 (OTTO) Cumene, 99%+ Cas no 98-82-8 - used in the manufacture of phenol, acetone, acetophenone, and methylstyrene.