Question

Identify lowest positive charge developed (indicated by $\partial, \partial_1, \partial_2, \partial_3$) due to inductive effect in following compounds: $\text{CH}_3-\text{CH}_2^{\delta_3} \rightarrow \text{CH}_2^{\delta_2} \rightarrow \text{CH}_2^{\delta_1} \rightarrow \text{Cl}^\delta$

• A. $\partial_2$
• B. $\partial_3$
• C. $\partial$
• D. $\partial_1$

Hint:

Always remember that the inductive effect is a short-range effect that quickly dies out along a saturated carbon chain. The further away a carbon atom is from the electronegative group, the less it feels its electron-withdrawing pull.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The problem presents a chlorobutane alkyl chain and asks us to identify which carbon atom experiences the smallest magnitude of partial positive charge ($\delta^+$) resulting from the permanent inductive effect of the highly electronegative chlorine atom.

Step 2: Key Formula or Approach:
The inductive effect ($-I$ effect in this case) operates through $\sigma$-bonds. It is a distance-dependent phenomenon that diminishes rapidly as the distance from the electron-withdrawing atom increases: $$\delta_1^+ \gt \delta_2^+ \gt \delta_3^+ \dots$$

Step 3: Detailed Explanation:
Chlorine (Cl) is highly electronegative, creating a partial negative charge ($\delta^-$) on itself and drawing electron density away from the adjacent carbon. The carbon atom directly attached to the chlorine atom ($\text{C}_1$) experiences the strongest pull, developing the highest partial positive charge ($\delta_1^+$). This carbon ($\text{C}_1$) compensates by drawing electron density from the next carbon ($\text{C}_2$), which develops a weaker partial positive charge ($\delta_2^+$). This transmits further down to $\text{C}_3$, developing an even smaller partial positive charge ($\delta_3^+$). Beyond the third or fourth carbon atom, the inductive effect becomes virtually negligible. Comparing the magnitudes: $\delta_1^+ \gt \delta_2^+ \gt \delta_3^+$. Therefore, the lowest positive charge is developed at $\delta_3$.

Step 4: Final Answer:
The lowest partial positive charge is $\partial_3$, which corresponds to option (B).