Determine whether the diene given below is in the s-cis or s-trans conformation. Draw the s-cis conformation of the diene if it is in the s-trans conformation.

Which one, between buta-1,2-diene and buta-1,3-diene, would you expect to exhibit a higher heat of hydrogenation?

Provide a suitable allylic halide and a Grignard reagent that could be used to synthesize (E)-1-(but-2-en-1-yl)-1-methylcyclopentane.

Draw the substitution and elimination products formed in the following reaction:

1-(bromomethyl)-2-methylcyclohex-1-ene heated with methanol

Give the products of the reaction shown below (ignore stereoisomers and assume one equivalent of each reagent):

The intramolecular Diels-Alder reaction is a notable version of such a reaction in which the diene and the dienophile are in the same molecule. This type of Diels-Alder reaction forms two new rings. If the following molecules undergo Diels-Alder reactions, draw the compound produced, including its stereochemistry. [Note: Lewis acid catalysts are utilized. However, we will ignore this in this case.]

Draw the structures of the major products in the given chemical reactions.

Show the mechanism and find out the possible reactants for producing the following compound using a Diels–Alder reaction.

a. Draw the end lobes of molecular orbitals of conjugated π-bonds in the following to show whether the HOMO is symmetric or antisymmetric.

i. A polyene with even numbers of π-bonds.

ii. A polyene with odd numbers of π-bonds.

b. Do these MOs follow the Woodward–Hoffmann rules given below?

Woodward–Hoffmann rules:

• For an even number of π-bonds, an electrocyclic reaction occurs thermally with a conrotatory ring closure and photochemically with disrotatory ring closure.
• For an odd number of π-bonds electrocyclic reaction thermally with a disrotatory ring closure and photochemically with conrotatory ring closure.

Draw the π molecular orbitals of octa-1,3,5,7-tetraene.

Arrange the following compounds in decreasing order of λ_max.

Answer the following questions considering the molecular orbital diagram shown:

i. List the bonding MOs and the antibonding MOs.

ii. List the symmetric MOs and antisymmetric MOs.

iii. Identify the HOMO and LUMO.

Identify the number of nodes in each of the MOs of the indicated carbons.

An unknown compound weighing 0.0020 g with a molecular weight approximately equal to glucose (180 g/mol) was dissolved in water with a total volume of about 5.0 × 10² mL. A portion of this solution was placed in a 1.0 cm cell, and the UV spectrum was measured. The solution had λ_max = 260 nm, with A = 1.0. Calculate the molar absorptivity at 260 nm.

Why is the [2 + 2] cycloaddition between two but-2-ene molecules photochemically allowed but thermally forbidden?

Maleic anhydride does not react with but-2-ene but reacts rapidly with 2,3-dimethylbuta-1,3-diene under thermal conditions. Why do these observations occur under thermal conditions?

Will 2,3-dimethyl-1,3-butadiene and 2-cyclohexene-1,4-dione have a concerted reaction in the presence of UV light?

Give the product of the reaction shown below:

Provide the product of the reaction shown below:

Determine the manner in which the ring is closed for the given electrocyclic reaction.

A chemist observed that when a certain isomer was heated, the deuterium atom was found to be distributed across all three positions on the five-membered ring. Suggest a plausible mechanism to explain this phenomenon.

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

Provide the mechanism of the following reaction.