Chapter 24, Problem 24.1YT

Interpretation Introduction

Interpretation:

The elementary step in Equation 24-2 to depict a counterclockwise movement of the electrons is to be drawn. If this alternate way of drawing the curved arrows leads to the same product as shown in Equation 24-2 is to be explained.

Concept introduction:

Ethene reacts with buta-1, 3-diene, a conjugated diene, to form cyclohexene. This is the simplest example of what is called the Diels–Alder reaction. This reaction is so important in organic chemistry that Otto Diels (1876–1954) and Kurt Alder (1902–1958), the two German chemists who first described the reaction, shared the 1950 Nobel Prize in Chemistry. The Diels–Alder reaction is especially useful because it forms two new carbon-carbon bonds.

Diels-Alder reactions can be carried out under mild conditions. The reaction is stereospecific and often regioselective, which can provide chemists substantial control over the products that are formed. The mechanism for the simplest possible Diels-Alder reaction (shown in Equation 24-1) is provided in Equation 24-2. This serves as the prototype for all other Diels-Alder reactions.