Show how the following compounds can be prepared from the given starting material.
b.

Verified step by step guidance

1. Step 1: Begin with the starting material, pyridine. Pyridine is an aromatic heterocyclic compound with a nitrogen atom in the ring. The target molecule requires substitution at two positions: bromination at the 3-position and amination at the 4-position.
2. Step 2: Perform selective bromination of pyridine. Use a brominating agent such as Br2 in the presence of a catalyst like FeBr3 or AlBr3. This reaction introduces a bromine atom at the 3-position of pyridine due to the electronic effects of the nitrogen atom, which directs substitution to the meta position.
3. Step 3: Introduce the amino group at the 4-position. This can be achieved through nucleophilic substitution. First, convert the bromine atom at the 3-position into a leaving group by activating the pyridine ring. Then, use ammonia (NH3) or an amine source to replace the leaving group with an amino group at the 4-position.
4. Step 4: Ensure regioselectivity during the amination step. The nitrogen atom in pyridine influences the reactivity of the ring, and the reaction conditions must be carefully controlled to avoid substitution at undesired positions.
5. Step 5: Purify the final product using techniques such as recrystallization or chromatography to isolate 3-bromo-4-aminopyridine. Confirm the structure using spectroscopic methods like NMR or IR to ensure the correct substitution pattern.

Key Concepts

Synthetic Pathways

Synthetic pathways refer to the series of chemical reactions that transform a starting material into a desired product. Understanding these pathways is crucial for predicting how specific compounds can be synthesized, as they involve various reaction mechanisms, reagents, and conditions that dictate the outcome of the synthesis.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. Identifying functional groups in both the starting material and the target compounds is essential for determining the appropriate reactions and reagents needed for synthesis.

Reaction Mechanisms

Reaction mechanisms describe the step-by-step sequence of events that occur during a chemical reaction. A solid understanding of these mechanisms allows chemists to predict the products of reactions, optimize conditions, and troubleshoot potential issues in the synthesis process.