2-Undecanone is an oily organic liquid manufactured synthetically, but which can also be extracted from oil of rue. It is found naturally in bananas, cloves, ginger, guava, and strawberries. 2-Undecanone is used in the perfumery and flavoring industries, but because of its strong odor it is primarily used as an insect or animal repellant. Typically, 1–2% concentrations of 2-undecanone are found in dog and cat repellents in the form of a liquid, aerosol spray, or gel.
2-Undecanone is a ketone, also known as methyl nonyl ketone (MNK). It is soluble in ethanol, benzene, chloroform, and acetone, but its large carbon chain renders it insoluble in water. Like most methyl ketones, 2-undecanone undergoes a haloform reaction when in the presence of a base. For example, the reaction between 2-undecanone and sodium hypochlorite yields sodium decanoate, chloroform, and sodium hydroxide.
CH3CO(CH2)8CH3 + 3NaOCl → CH3(CH2)8COONa + CHCl3 + 2NaOH