Question

Select the option in which all the given functional groups exhibit \(+R\) effect.

• A. \(-OH,\; -NH_2,\; -OCOR,\; -NHCOR\)
• B. \(-OH,\; -NH_2,\; -NO_2,\; -NR_2\)
• C. \(-CHO,\; -NHR,\; -OR,\; -OCOR\)
• D. \(-NHR,\; -COOH,\; -NHCOR,\; -OR\)

Hint:

Groups having lone pairs directly attached to the aromatic ring generally exhibit \(+R\) effect. \[ -OH,\; -OR,\; -NH_2,\; -NHR,\; -NR_2 \] whereas \[ -NO_2,\; -CHO,\; -COOH,\; -COR \] show \(-R\) effect.

Answer 1

The Correct Option is A

Step 1: Recall the rule for $+R$.
A group shows positive resonance ($+R$) when it has a lone pair on the atom directly attached to the ring and can push that lone pair into the ring.

Step 2: Spot the lone-pair donors.
$-OH$, $-NH_2$, $-OR$ and the nitrogen and oxygen of $-NHCOR$ and $-OCOR$ all carry a lone pair on the attached atom, so each can donate by resonance.

Step 3: Rule out withdrawers.
Groups like $-NO_2$, $-CHO$ and $-COOH$ pull electrons out of the ring, so they are $-R$ groups, not $+R$.

Step 4: Test each option.
The option with $-NO_2$ is out, the one with $-CHO$ is out, and the one with $-COOH$ is out.

Step 5: Check the survivor.
The set $-OH, -NH_2, -OCOR, -NHCOR$ has every group carrying a donatable lone pair on the attached atom, so all four are $+R$.

Step 6: State the answer.
That first option is the correct all-$+R$ set.
\[ \boxed{-OH,\ -NH_2,\ -OCOR,\ -NHCOR} \]