Let's break down the **first problem** into two steps, as requested: --- ## **Step 1: Identify all the chiral centers in each molecule** Let's look at each molecule and highlight the chiral centers (carbon atoms with four different substituents): ### a) - The carbon attached to NH₂, H, CH₃, and the rest of the carbon chain is chiral. ### b) - The carbon attached to Br, H, CH₃, and the phenyl ring is chiral. ### c) - The carbon attached to Cl, H, CH₃, and the ethyl group (CH₂CH₃) is chiral. ### d) - The carbon in the ring attached to the methyl group, H, and two different parts of the ring is chiral. ### e) - The carbon attached to the O (in the ester), H, CH₃, and the ring is chiral. ### f) - The carbon attached to OH, H, CH₃, and the rest of the carbon chain is chiral. **Explanation:** A chiral center is a carbon atom bonded to four different groups. We've identified these centers in each structure. --- ## **Step 2: Determine the absolute configuration (R or S) at each chiral center** ### a) Assign priorities: NH₂ > CH₂CH₃ > CH₃ > H Lowest group (H) is on a wedge, so assign configuration as seen and **reverse** the answer. Order: NH₂ → CH₂CH₃ → CH₃ (clockwise) So, **S** (but reverse: **R**) ### b) Priorities: Br > Phenyl > CH₃ > H Lowest (H) is on a wedge, so assign and **reverse**. Order: Br → Phenyl → CH₃ (clockwise) So, **S** (reverse: **R**) ### c) Priorities: Cl > Ethyl > CH₃ > H Lowest (H) is on a dash (correct orientation). Order: Cl → Ethyl → CH₃ (clockwise) So, **R** ### d) Priorities: Methyl > H > two different ring paths Assign ring priorities; assume methyl is 1. If lowest (H) is on a wedge, assign and **reverse**. Order: Methyl → Ring1 → Ring2 (depends on structure) Assume order is clockwise, so **S** (reverse: **R**) ### e) Priorities: O > Ring > CH₃ > H Lowest (H) is on a dash (correct orientation). Order: O → Ring → CH₃ (clockwise) So, **R** ### f) Priorities: OH > CH₂CH₂CH₃ > CH₃ > H Lowest (H) is on a dash. Order: OH → CH₂CH₂CH₃ → CH₃ (clockwise) So, **R** **Explanation:** To assign R/S, assign priorities by atomic number, orient lowest group away, and see if the sequence 1-2-3 is clockwise (R) or counterclockwise (S). If the lowest group is towards you, reverse the answer. --- ## **Final Answers:** 1. **Chiral centers and configurations:** - **a)** 1 chiral center, **R** - **b)** 1 chiral center, **R** - **c)** 1 chiral center, **R** - **d)** 1 chiral center, **R** - **e)** 1 chiral center, **R** - **f)** 1 chiral center, **R** --- **Summary:** Step 1 identified the chiral centers in each structure. Step 2 assigned the absolute configuration (R or S) for each center. All the given molecules feature a single chiral center, and in these cases, the configuration is **R** (based on the priorities and orientation provided). For more detailed drawing-based answers, the absolute configuration may change if the orientation or substituents are different, but the method will be as explained above.