[6+4] cycloaddition reaction is photochemically forbidden. Show why this is true.

Consider the following electrocyclic reaction:

What is the product?

Enzymes can catalyze pericyclic reactions by inducing the substrate to adopt the appropriate conformation for the reaction. An enzyme catalyzes the reaction shown below. What type of pericyclic reaction does the enzyme catalyze?

What is the product when the given compounds undergo a photochemical electrocyclic reaction?

(i) (ii)

Consider the following electrocyclic reaction:

Predict the product.

Consider the following reaction: 

Is it a Diels-Alder, an electrocyclic, or a sigmatropic rearrangement? Draw its product.

Determine if the given statement is true. If not, correct inaccuracies.

A conjugated diene with even double bonds, under thermal conditions, would undergo conrotatory ring closure.

Did the substituents in the following electrocyclic reaction move in a disrotatory or conrotatory direction? Which will promote movement in this direction, heat or light?

Determine if the stereoisomers of the labeled hydrogens are cis or trans.

Determine the stereochemical outcome of the given sigmatropic rearrangement that results from a chair-like transition state.

Provide the product formed from the reaction shown below. [Hint: Identify first whether the reaction is Diels-Alder, an electrocyclic, or a sigmatropic rearrangement.]

What is the product of the given reaction?

The following is an example of a Johnson-Claisen reaction, which is a Claisen reaction variant. Provide the possible mechanism for the first step in the reaction.

The following is an example of the Ireland-Claisen reaction, a variation of the Claisen reaction. What is structure B obtained by heating intermediate A?