÷ÈÓ°Ö±²¥

Question: What product is formed when each compound undergoes thermal electrocyclic ring opening or ring closure? Label each process as conrotatory or disrotatory and clearly indicate the stereochemistry around tetrahedral stereogenic centers and double bonds.

Question: Draw the product of each electrocyclic reaction.

a. the thermal electrocyclic ring closure of (2E,4Z,6Z)-nona-2,4,6-triene

b. the photochemical electrocyclic ring closure of (2E,4Z,6Z)-nona-2,4,6-triene

c. the thermal electrocyclic ring-opening of cis-5-ethyl-6-methylcyclohexa-1,3-diene

d. the photochemical electrocyclic ring-opening of trans-5-ethyl-6-methylcyclohexa-1,3- diene

Question: Consider the following electrocyclic ring closure. Does the product form by a conrotatory or disrotatory process? Would this reaction occur under photochemical or thermal conditions?

Question: What type of cycloaddition occurs in Reaction [1]? Draw the product of a similar process in Reaction [2]. Would you predict that these reactions occur under thermal or photochemical conditions?

Question: Draw the product of each Diels–Alder reaction and indicate the stereochemistry at all stereogenic centers

Question: (a) How many π molecular orbitals are present in deca-1,3,5,7,9-pentaene $\mathbf{(}{\mathbf{CH}}_2\mathbf{=}\mathbf{CH}\mathbf{-}\mathbf{CH}\mathbf{=}\mathbf{CH}\mathbf{-}\mathbf{CH}\mathbf{=}\mathbf{CH}\mathbf{-}\mathbf{CH}\mathbf{=}\mathbf{CH}\mathbf{-}\mathbf{CH}\mathbf{=}{\mathbf{CH}}_2\mathbf{)}$? (b) How many are bonding MOs and how many are antibonding MOs ? (c) How many nodes are present in ${\mathbf{\text{ψ}}}_{\mathbf{1}}^{\mathbf{*}}$? (d) How many nodes are present in ${\mathbf{ψ}}_{10}^{*}$?

Question: Draw the product of the [3,3] sigmatropic rearrangement of each compound.

Question: A solution of 5-methylcyclopenta-1,3-diene rearranges at room temperature to a mixture containing 1-methyl-, 2-methyl-, and 5-methylcyclopenta-1,3-diene. (a) Show how both isomeric products are formed from the starting material by a sigmatropic rearrangement involving a C–H bond. (b) Explain why 2-methylcyclopenta-1,3-diene is not formed directly from 5-methylcyclopenta-1,3-diene by a [1,3] rearrangement.

Question: What product is formed from the $\left[5,5\right]$ sigmatropic rearrangement of the following unsaturated ether?

Question: Use curved arrows and draw the product of each electrocyclic reaction.