An organic compound containing 92.3% of C, 7.7% of H had the molecular weight 26. When treated with bromine, it gave a product containing 92.5% of bromine but when treated with HBr, it gave a product containing 85.1% of bromine. What is the structural formula of the organic compound ?

Answer

To determine the structural formula of the organic compound based on the given information, we can follow these steps:

### Step 1: Determine the Empirical Formula
Given the percentages of carbon (C) and hydrogen (H):
- C = 92.3%
- H = 7.7%

To find the empirical formula, we first convert these percentages to moles by dividing by their respective atomic weights:
- Atomic weight of C = 12 g/mol
- Atomic weight of H = 1 g/mol

Calculating the moles:
- Moles of C = 92.3 g / 12 g/mol = 7.692
- Moles of H = 7.7 g / 1 g/mol = 7.7

### Step 2: Normalize the Mole Ratios
Next, we need to find the simplest whole number ratio by dividing each mole value by the smallest number of moles calculated:
- Smallest number of moles = 7.692 (for C)
- Ratio of C = 7.692 / 7.692 = 1
- Ratio of H = 7.7 / 7.692 = 1.001 (approximately 1)

Thus, the empirical formula is CH.

### Step 3: Calculate the Empirical Formula Weight
Now we calculate the empirical formula weight:
- Empirical formula weight of CH = 12 (for C) + 1 (for H) = 13 g/mol

### Step 4: Determine the Molecular Formula
Given that the molecular weight of the compound is 26 g/mol, we can find the value of n:
- n = Molecular weight / Empirical formula weight = 26 g/mol / 13 g/mol = 2

Thus, the molecular formula is:
- C2H2 (since we multiply the empirical formula by n).

### Step 5: Analyze the Reaction with Bromine and HBr
When treated with bromine (Br2), the product contains 92.5% bromine. When treated with HBr, the product contains 85.1% bromine. This suggests that the compound is likely an alkene or alkyne, which can react with bromine and HBr.

### Step 6: Determine the Structural Formula
The molecular formula C2H2 corresponds to ethyne (acetylene), which has the structural formula:
- H-C≡C-H (triple bond between the two carbon atoms).

### Conclusion
The structural formula of the organic compound is:
- **C2H2 (ethyne or acetylene)**, with the structural representation being **H-C≡C-H**.

---