Two isomeric compounds (A) and (B) have `C_(4)H_(11)N` as molecular formula. Both on separately treating with `HNO_(2)` lose their `N_(2)` producing two isomeric alcohols (C) and (D) respectively of molecular formula `C_(4)H_(10)O`. (C) reacts with Lucas reagent immediately and units oxidation. (D) does not reacts with Lucas reagent in cold but can be easily oxidized. Complete methylation of either (A) or (B) is made which on decomposition does not produce 1-butene. Identify A to D.

Answer

To solve the problem, we need to identify the isomeric compounds A and B, as well as the alcohols C and D that result from their reactions with HNO2. Let's break down the solution step by step.

### Step 1: Identify the Isomeric Compounds A and B
Given the molecular formula C4H11N, we can deduce that the compounds are amines. The possible structural isomers for C4H11N include:
1. Butylamine (n-butylamine)
2. Isobutylamine
3. Sec-butylamine
4. Tert-butylamine

Since we are looking for two isomeric compounds, we can choose:
- A: 2-Methylpropylamine (isobutylamine)
- B: 1-Butylamine (n-butylamine)

### Step 2: Reaction with HNO2
Both compounds A and B react with nitrous acid (HNO2) to form alcohols C and D, respectively. The reaction involves the loss of nitrogen gas (N2) and the formation of alcohols.

- For A (2-Methylpropylamine), the reaction produces:
- C: 2-Methylpropan-1-ol (tert-butyl alcohol)

- For B (1-Butylamine), the reaction produces:
- D: Butan-1-ol (a primary alcohol)

### Step 3: Analyze Alcohols C and D
Now we have:
- C: 2-Methylpropan-1-ol (tert-butyl alcohol)
- D: Butan-1-ol (a primary alcohol)

### Step 4: Reactivity with Lucas Reagent
- Alcohol C (2-Methylpropan-1-ol) reacts immediately with Lucas reagent (which contains zinc chloride in hydrochloric acid) because it is a tertiary alcohol.
- Alcohol D (Butan-1-ol) does not react with Lucas reagent in cold conditions because it is a primary alcohol, but it can be oxidized easily.

### Step 5: Complete Methylation
The problem states that complete methylation of either A or B does not produce 1-butene upon decomposition. This suggests that the structure of the amine does not lead to the formation of 1-butene.

### Final Identification
Based on the above analysis, we can summarize the identification of the compounds:
- A: 2-Methylpropylamine (isobutylamine)
- B: 1-Butylamine
- C: 2-Methylpropan-1-ol (tert-butyl alcohol)
- D: Butan-1-ol

### Summary of Identified Compounds
- **A**: 2-Methylpropylamine (C4H11N)
- **B**: 1-Butylamine (C4H11N)
- **C**: 2-Methylpropan-1-ol (C4H10O)
- **D**: Butan-1-ol (C4H10O)