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Current Question (ID: 10913)

Question:
$\text{The correct reactivity order towards hydrolysis is:}$ $\text{(P) } \text{Cl-benzene with NO}_2 \text{ at meta position}$ $\text{(Q) } \text{CH}_2\text{Cl-benzene with OCH}_3 \text{ at para position}$ $\text{(R) } \text{Cl-benzene with NO}_2 \text{ at para position}$ $\text{(S) } \text{CH}_2\text{Cl-benzene with OCH}_3 \text{ at meta position}$
Options:
  • 1. $\text{Q}>\text{R}>\text{S}>\text{P}$
  • 2. $\text{Q}>\text{P}>\text{R}>\text{S}$
  • 3. $\text{S}>\text{R}>\text{Q}>\text{P}$
  • 4. $\text{Q}>\text{S}>\text{R}>\text{P}$ (Correct)
Solution:
$\text{Hint: Reactivity order towards hydrolysis is depends on the stability of carbocation}$ $\text{Hydrolysis can be considered as a nucleophilic substitution reaction in which Cl}^- \text{ is replaced by OH}^- \text{ ions. Options Q and S are benzyl halides which are more reactive in nucleophilic substitution due to the stability of carbocation formed. (A benzyl carbocation can be stabilized through resonance and the positive charge gets delocalized in the ring).}$ $\text{Q is the most reactive among all because the carbocation can be more stabilized through the +R effect of the methoxy present at para and it is not possible at meta. Options P and R are aryl halides, which are less reactive towards nucleophilic substitution due to many factors such as instability of phenyl carbocation, sp}^2 \text{ hybridized carbon, resonance effect, etc.}$ $\text{The presence of EWG like NO}_2 \text{ increases the reactivity as the intermediate formed(a negatively charged sigma complex, called Meisenheimer complex) can be stabilized through the -R effect. This is more pronounced at ortho and para than meta. So R is more reactive than P.}$ $\text{The order is Q}>\text{S}>\text{R}>\text{P}$

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Expected JSON Format:

{
  "question": "The mass of carbon present in 0.5 mole of $\\mathrm{K}_4[\\mathrm{Fe(CN)}_6]$ is:",
  "options": [
    {
      "id": 1,
      "text": "1.8 g"
    },
    {
      "id": 2,
      "text": "18 g"
    },
    {
      "id": 3,
      "text": "3.6 g"
    },
    {
      "id": 4,
      "text": "36 g"
    }
  ],
  "solution": "\\begin{align}\n&\\text{Hint: Mole concept}\\\\\n&1 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\text{ moles of carbon atom}\\\\\n&0.5 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\times 0.5 \\text{ mol} = 3 \\text{ mol}\\\\\n&1 \\text{ mol of carbon} = 12 \\text{ g}\\\\\n&3 \\text{ mol carbon} = 12 \\times 3 = 36 \\text{ g}\\\\\n&\\text{Hence, 36 g mass of carbon present in 0.5 mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6].\n\\end{align}",
  "correct_answer": 4
}