A: Due to ortho effect basic nature of aniline decreases.
R: It is due to steric hinderance because of solvation of cation.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To analyze the given statements regarding the basic nature of aniline and the ortho effect, we will break down the concepts step by step.

### Step 1: Understanding Aniline and Its Basicity
Aniline (C6H5NH2) is an aromatic amine where the amino group (-NH2) is attached to a benzene ring. The basicity of aniline is due to the lone pair of electrons on the nitrogen atom, which can accept a proton (H+).

**Hint:** Remember that basicity is related to the ability of a compound to donate a lone pair of electrons to a proton.

### Step 2: The Ortho Effect
The ortho effect refers to the observation that ortho-substituted anilines (where a substituent is at the ortho position relative to the amino group) are generally weaker bases compared to aniline itself. This is because the substituent at the ortho position can create steric hindrance when the amine tries to accept a proton.

**Hint:** Consider how the position of substituents on the benzene ring affects the spatial arrangement and interactions during protonation.

### Step 3: Steric Hindrance and Solvation
When an ortho substituent is present, it can hinder the approach of protons to the nitrogen atom. This steric hindrance makes it more difficult for the nitrogen to effectively bond with a proton, thus decreasing the basicity. Additionally, when the nitrogen does accept a proton, the resulting cation (the conjugate acid) experiences solvation, where water molecules surround it. This solvation can further stabilize the cation but also makes it bulkier, exacerbating the steric hindrance.

**Hint:** Think about how the size and shape of molecules influence their interactions, especially in a polar solvent like water.

### Step 4: Conclusion on the Assertion and Reason
Given the above points, we can conclude that:
- The assertion (A) that the basic nature of aniline decreases due to the ortho effect is true.
- The reason (R) that this decrease is due to steric hindrance from solvation of the cation is also true and correctly explains the assertion.

Thus, both statements are true, and the reason provided is a valid explanation for the assertion.

**Final Answer:** Both assertion and reason are true, and the reason is the correct explanation for the assertion.