This is a Diels-Alder reaction; these reactions happen between a nucleophilic diene, shown in blue below, and an electrophilic dienophile, in green. Diels-Alder reactions install a set of bonds that connect each external carbon of the diene system to an alkene carbon in the dienophile system to create a new six-membered ring. All remaining structure of the two reactants are retained, including the six- and five-membered rings below. The red bonds are the newly installed bonds.

The electrons from one of the double bonds on the 1,3-dibutene create a new single bond. The other new single bond is created from the electrons in the double bond of the other reactant. These two new single bonds join the reactants to create a cyclic product.

The electrons from the other double bond in the 1,3-dibutene move between the carbon 2 and 3. Thus, the final product is a 6-carbon cycloalkene with a halogen substituent.

This is a standard Diels-Alder reaction. Diels-Alder reactions are driven solely by adding heat to the reagents. By looking at the reagents and the product, we can tell that this is a Diels-Alder reaction. For Diels-Alder, we need a cis-diene and an alkene as reactants. When these reactants are stimulated by heat, they form a cyclohexene product.

This is a classic Diels-Alder reaction and it consists of a diene (cyclopentadiene) and a dienophile (ethene). The bicyclic structure forms if the electrons are moved in a circular fashion.

Diels-Alder reactions create cyclohexene rings (eliminate III, IV, and V), and starting dienophile is trans (E conformation), so product is E (Eliminate I).

The Diels-Alder reaction converts a conjugated diene and a substituted alkene into a six-membered ring containing cyclohexene (a substituted cyclohexene system). In Hoffmann elimination, tetra-alkyl ammonium salts undergo elimination to form the least substituted alkene. The Wittig reaction uses phosphorus ylides, aldehydes, or ketones to form an alkene and a triphenylphosphine oxide. Lastly, Gabriel synthesis forms primary amines via the reaction of a phthalimide with an alkyl halide, followed by cleavage with hydrazine.

Ozonolysis is essentially used to cleave a compound at the location of a double bond. For the result to be a single product, the cleavage must occur at a point of symmetry.

4-octene, a symmetrical alkene, would give two equivalents of butanal upon ozonolysis. All of the other compounds are unsymmetrical and would give at least two different non-identical products.

Ozonolysis of the alkyne breaks the alkyne at the triple bond. The carbons that were in the triple bond become the carbons of either a ketone or a carboxylic acid depending on if they are terminal or not.

Working backwards, one can take the products and remove their oxygens. Then, the carbons from which the oxygens were removed should be triple bonded. The initial compound has seven carbons in its longest chain. Counting from the side closest to the bond, C2 has two methyl groups bound to it. The triple bond runs across C3 and C4. Thus the answer is 2,2-dimethyl-3-heptyne.

These are standard conditions for an ozonolysis reaction. For an ozonolysis reaction to take place, all we need is an alkene and ozone. The ozone essentially cuts the alkene in half and adds a carbonyl group to each half of the carbon chain.

Only bromocyclohexane is created because there is only one bromine group that bonds with one of the carbons, while the other carbon is bonded with hydrogen group.