### Exercise A For each of the following: a. **Predict products following HBr addition.** (Will there be just one, or more than one?) b. **Draw mechanisms.** Be sure to draw both versions of the allylic cation. c. **Identify 1,2 versus 1,4 addition products.** d. **Identify thermodynamic product.** #### Explanation: - **HBr Addition:** This refers to the addition of hydrogen bromide across a double bond in an alkene, leading to different structural outcomes depending on reaction conditions and intermediates. - **Mechanisms:** The reaction mechanism should show the progression from reactants to the formation of intermediates (allylic cations in this case) and then to the final product. - **1,2 Versus 1,4 Addition Products:** These terms refer to the position where the new bonds form in relation to the original structure, which affects the stability and type of product formed. - **Thermodynamic Product:** The most stable product formed under the reaction's equilibrium conditions, often differing from the kinetically favored product. The image contains structural formulas of organic compounds: 4. The structure consists of a chain of carbon atoms with three alternating double bonds. One end of the chain is terminated with a "Ph" group, representing a phenyl group. 5. This structure features a three-carbon chain with two double bonds forming a "Y" shape, indicating an unsaturated hydrocarbon structure. 6. A six-membered ring with alternating double bonds is shown, representing a benzene ring with a single methyl group attached, indicating a toluene molecule. 7. The diagram displays a branched carbon chain with two double bonds and a terminal methyl group, indicating an unsaturated hydrocarbon with a branching point.