16. Conjugated Systems

b. Are the indicated hydrogens cis or trans?

1.

a. Identify the mode of ring closure for each of the following electrocyclic reactions

1.

Use the summary charts to predict the product of the following reactions. If there is more than one isomer possible, draw them

How can this transformation be carried out using only heat or light?

Which of the following are correct? Correct any false statements.

a. A conjugated diene with an even number of double bonds undergoes conrotatory ring closure under thermal conditions.

Explain why compound A will not undergo a ring-opening reaction under thermal conditions, but compound B will.

Predict the product for the following reaction.

a. Under thermal conditions, will ring closure of (2E,4Z,6Z,8E)-2,4,6,8-decatetraene be conrotatory or disrotatory?

b. Will the product have the cis or the trans configuration?

Use the summary charts to predict the product of the following reactions. If there is more than one isomer possible, draw them

Given the conditions, would you expect conrotatory or disrotatory ring closing/opening? Justify this on the basis of the molecular orbital picture.

(c)

Which of the following are correct? Correct any false statements.

b. A conjugated diene with an antisymmetric HOMO undergoes conrotatory ring closure under thermal conditions.

For the following electrocyclic reactions, did the substituents move in a conrotatory or disrotatory direction? Would you use heat or light to cause movement in this direction?

(a)

a. Identify the mode of ring closure for each of the following electrocyclic reactions

2.

Account for the difference in the products of the following reactions:

b. Are the indicated hydrogens cis or trans?

2.