Question

Identify $-\text{I}$ effect causing group from following.

• A. $-\text{COOR}$
• B. $-\text{CH}_3$
• C. $-\text{C}_2\text{H}_5$
• D. $-\text{C}_3\text{H}_7$

Hint:

Any functional group containing carbonyl features ($-\text{CHO}$, $-\text{COR}$, $-\text{COOH}$, $-\text{COOR}$) has a highly electronegative carbon center that strongly pulls shared valence electrons. Conversely, simple hydrocarbon alkyl tails are always classified as $+\text{I}$ chains.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
We are required to identify which structural functional group out of the given choices acts via a negative inductive effect ($-\text{I}$ effect), meaning it withdraws shared $\sigma$-electron density towards itself relative to a hydrogen atom reference.

Step 2: Detailed Explanation:
The inductive effect is an electronic phenomenon where electron density shifts through $\sigma$-bonds due to electronegativity discrepancies:

$-\text{I}$ Effect (Electron-Withdrawing): Groups that possess an electronegative heteroatom or a partial/full positive charge pull bonding electrons away from the carbon chain. An ester group ($-\text{COOR}$) features a highly polar carbonyl carbon bonded to two highly electronegative oxygen atoms. This layout creates a strong electron deficiency, causing the whole cluster to function as a powerful electron-withdrawing center via $\sigma$-bonds.

$+\text{I}$ Effect (Electron-Donating): Purely saturated alkyl chains push electron density toward the rest of the chemical structure. Therefore, groups such as methyl ($-\text{CH}_3$), ethyl ($-\text{C}_2\text{H}_5$), and propyl ($-\text{C}_3\text{H}_7$) are standard electron-donating groups that demonstrate a positive inductive effect ($+\text{I}$).
As a result, only the ester group ($-\text{COOR}$) exhibits a $-\text{I}$ effect.

Step 3: Final Answer: The negative inductive group is $-\text{COOR}$, which corresponds to option (A).