2,3-Pentanedione (acetyl propionyl) is a yellow liquid that exists in diketonic form. However, in some GC conditions, 2,3-pentanedione can appear in its enol form, i.e. 3-hydroxypent-3-en-2-one, up to a small percentage.
2,3-Pentanedione occurs in butter, bread, milk, yogurt, chicken, meat, cocoa, coffee, potato chips, roasted almonds, pecans, beer, red and white wine, rum and whiskey. The organoleptic profile can be described as creamy, penetrating, cheesy, oily, sweet, buttery, almondlike, brown roasted, and somewhat caramellic, with a fruity nuance.
2,3-Pentanedione belongs to the important family of α-diketones, which includes diacetyl, 2,3-hexanedione (acetylbutyryl), 3,4-hexanedione (dipropionyl), 2,3-heptanedione (acetyl valeryl) and 5-methyl-2,3-hexanedione (acetyl isovaleryl). Acetyl methyl carbinol (acetoin) could be also included in this group of materials.