The general formula of haloalkanes where X represents the halide is

Analysis of the Question

The question asks for the general molecular formula of haloalkanes (also known as alkyl halides). These are organic compounds derived from alkanes where one or more hydrogen atoms have been replaced by a halogen atom (represented by X).

Concept Explanation

1. Alkanes: The general formula for a saturated alkane is $C_nH_{2n+2}$.
2. Formation of Haloalkanes: To form a mono-haloalkane, you remove one hydrogen atom from an alkane molecule and replace it with a halogen atom (X).
3. Derivation: • Start with the alkane formula: $C_nH_{2n+2}$ • Subtract one hydrogen: $C_nH_{(2n+2)-1}$ which simplifies to $C_nH_{2n+1}$ • Add the halogen atom (X): $C_nH_{2n+1}X$

Step-by-Step Solution

• Step 1: Identify the parent hydrocarbon. Since haloalkanes are derived from alkanes, we start with the alkane general formula: $C_nH_{2n+2}$.
• Step 2: Apply the substitution rule. Replacing one hydrogen atom with a halogen (X) means we subtract 1 from the hydrogen count ($2n+2 - 1 = 2n+1$).
• Step 3: Combine the components. We get $C_nH_{2n+1} + X$, which is written as $C_nH_{2n+1}X$.

Comparing this to the given options:

• A: $C_nH_{2n-1}X$ (Incorrect)
• B: $C_nH_{2n}X$ (Incorrect)
• C: $C_nH_{2n+2}X$ (Incorrect - this would imply an extra bond)
• D: $C_nH_{2n+1}X$ (Correct)

Conclusion

The general formula for a mono-haloalkane is $C_nH_{2n+1}X$. This matches option D.

Exam Tip

Always remember that haloalkanes are "alkane-like." If you ever forget the formula, just pick a simple alkane like Methane ($CH_4$). Replace one Hydrogen with Chlorine ($Cl$) to get Chloromethane ($CH_3Cl$). Now, test the options by plugging in $n=1$:

• For $n=1$, $C_1H_{2(1)+1}X = CH_3X$. This matches our example!