Within each structure, rank the indicated nitrogens by increasing basicity.
(d)
(e)

Verified step by step guidance

1. Step 1: Analyze the structures provided. In the first image (atabrine), the nitrogens labeled H and I are part of different environments. Nitrogen H is part of an amine group directly attached to an aromatic ring, while nitrogen I is part of a tertiary amine group. In the second image, the nitrogens labeled J, K, and L are part of different environments: J is part of an amide group, K is part of a secondary amine in a cyclic structure, and L is part of a secondary amine with a hydrogen attached.
2. Step 2: Recall the factors affecting basicity. Basicity is influenced by electron density on the nitrogen atom, resonance effects, inductive effects, and steric hindrance. Nitrogens with higher electron density and less resonance delocalization are generally more basic.
3. Step 3: For the first structure (atabrine), nitrogen H is less basic than nitrogen I because nitrogen H is attached to an aromatic ring, which delocalizes its lone pair through resonance, reducing its electron density. Nitrogen I, being part of a tertiary amine, has no resonance effects and is more basic due to higher electron density.
4. Step 4: For the second structure, nitrogen J is the least basic because it is part of an amide group, where the lone pair on nitrogen is delocalized into the carbonyl group, significantly reducing its electron density. Nitrogen K is more basic than J because it is part of a secondary amine in a cyclic structure, but it is less basic than nitrogen L due to steric hindrance and the cyclic environment. Nitrogen L is the most basic because it is a secondary amine with a hydrogen attached, allowing for higher electron density and minimal steric hindrance.
5. Step 5: Rank the nitrogens in each structure by increasing basicity. For the first structure: H < I. For the second structure: J < K < L.

Key Concepts

Basicity of Nitrogen Compounds

Basicity refers to the ability of a nitrogen atom to accept protons (H+). In organic chemistry, the basicity of nitrogen is influenced by its hybridization, electronegativity, and the presence of electron-donating or withdrawing groups. Generally, sp3-hybridized nitrogens are more basic than sp2 or sp-hybridized ones due to the availability of lone pair electrons for protonation.

Inductive Effect

The inductive effect describes how the presence of electronegative atoms or groups can withdraw electron density from adjacent atoms, affecting their reactivity and basicity. Electron-withdrawing groups decrease basicity by stabilizing the lone pair on nitrogen, while electron-donating groups enhance basicity by increasing electron density around the nitrogen atom, making it more likely to accept protons.

Resonance Stabilization

Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, leading to delocalization of electrons. In nitrogen-containing compounds, resonance can significantly affect basicity; if the lone pair on nitrogen is involved in resonance with other atoms, it becomes less available for protonation, thus decreasing the basicity of that nitrogen.