The mechanism for the conversion of propanedial from its keto form to its enol form under basic and acidic conditions is to be drawn. Similarly, the mechanism for the conversion of propanedial from its enol form to the keto form is to be drawn. Concept introduction: In the enol form, the species has a carbon atom that is simultaneously a part of a C = C bond, characteristic of an alkene , and is bonded to OH, characteristic of an alcohol. In the keto form, there is a hydrogen atom on the carbon atom that is adjacent to the C = O group, so called alpha carbon, whereas in the enol form, the hydrogen appears on the oxygen atom instead. The proton transfer step serves to add or remove a proton from the particular species. The mechanism of this transformation depends on the presence of a strong acid or strong base. In the basic condition, the strong base removes a proton from the α carbon of the species in the keto form, producing an enolate anion having a negative charge. In the resonance structure of this anion, the electron-rich atom gains a proton from water, which acts as an acid and forms its enol form. In the acidic condition, the strong acid donates a proton to the O atom of the C = O group of the keto form. Then water removes the proton from the α carbon to produce enol from of the species. These reactions take place in reverse direction in the transformation of the enol form to the keto form.

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Chapter 7, Problem 7.44P

Interpretation Introduction

Interpretation:

The mechanism for the conversion of propanedial from its keto form to its enol form under basic and acidic conditions is to be drawn. Similarly, the mechanism for the conversion of propanedial from its enol form to the keto form is to be drawn.

Concept introduction:

In the enol form, the species has a carbon atom that is simultaneously a part of a C = C bond, characteristic of an alkene, and is bonded to OH, characteristic of an alcohol. In the keto form, there is a hydrogen atom on the carbon atom that is adjacent to the C = O group, so called alpha carbon, whereas in the enol form, the hydrogen appears on the oxygen atom instead. The proton transfer step serves to add or remove a proton from the particular species. The mechanism of this transformation depends on the presence of a strong acid or strong base. In the basic condition, the strong base removes a proton from the α carbon of the species in the keto form, producing an enolate anion having a negative charge. In the resonance structure of this anion, the electron-rich atom gains a proton from water, which acts as an acid and forms its enol form. In the acidic condition, the strong acid donates a proton to the O atom of the C = O group of the keto form. Then water removes the proton from the α carbon to produce enol from of the species. These reactions take place in reverse direction in the transformation of the enol form to the keto form.

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