METHYL ISOBUTYL KETONE 4L - 253-4, 4 L. 4-Methyl-2-Pentanone. Methyl isobutyl ketone. CAS RN 108-10-1. Formula Weight: 100.16. B&J Brand, 99.0% min. by GC. For HPLC, GC, spectrophotometry, and metal complex extraction for atomic absorption spectrosco