Predict the product of the Diels–Alder reactions shown.
(a)

Verified step by step guidance

1. Identify the diene and the dienophile in the reaction. The diene is a conjugated system with two double bonds, and the dienophile is typically an alkene or alkyne with electron-withdrawing groups.
2. Ensure the diene is in the s-cis conformation, which is necessary for the Diels-Alder reaction to occur. If it is not, consider any possible rotations or conformational changes.
3. Align the diene and dienophile so that the p orbitals can overlap effectively. This involves bringing the diene and dienophile close together in a way that allows for the formation of new sigma bonds.
4. Draw the transition state of the reaction, showing the cyclic overlap of the p orbitals. This is a concerted process where bonds are broken and formed simultaneously.
5. Predict the product by forming a six-membered ring. The new sigma bonds form between the ends of the diene and the dienophile, resulting in a cyclohexene derivative. Consider any stereochemistry involved, as the reaction is stereospecific.

Key Concepts

Diels–Alder Reaction

The Diels–Alder reaction is a [4+2] cycloaddition between a conjugated diene and a dienophile, typically forming a six-membered ring. It is a pericyclic reaction that proceeds via a concerted mechanism, meaning bonds are formed simultaneously without intermediates. This reaction is stereospecific, often preserving the stereochemistry of the reactants in the product.

Conjugated Diene

A conjugated diene consists of two double bonds separated by a single bond, allowing for electron delocalization across the π-system. This delocalization stabilizes the diene and makes it reactive in cycloaddition reactions like the Diels–Alder. The s-cis conformation of the diene is crucial for effective overlap with the dienophile's π-orbitals during the reaction.

Dienophile

A dienophile is an alkene or alkyne that reacts with a diene in the Diels–Alder reaction. It typically contains electron-withdrawing groups that enhance its reactivity by making the π-bond more electrophilic. The stereochemistry of the dienophile influences the stereochemistry of the resulting cyclohexene product, making its orientation important in predicting the reaction outcome.