Principle

Keto-enol tautomerism is understood in chemistry as the equilibrium between the structural form of an aldehyde and a ketone (the compounds must be constitution isomers). The name "enol" reflects the double bond (-en) and the OH group (-ol) in the molecular structure.

In this experiment, students learn a simple method of detection double and multiple bonds in organic substances and also to detect the keto-enol tautomerism for ethyl acetoacetate. Therefore bromine water is added to the ester solution and the double bond character of the enol form is detected. The use of bromine water for the detection of unsaturated hydrocarbons (for example, alkenes) allows to illustrate the double bond or multiple bond character of an organic compound. During the reaction the (intense) red-brown color of the bromine disappears and confirms the keto-enol tautomerism

Learning objectives

• Keto-enol tautomerism
• Properties of 3-oxobutanoic acid ethyl ester
• Detection of double bonds with bromine