Question

CH$_3$–Br $\xrightarrow{\text{CH$_3$OH/Nu}}$ CH$_3$OH 
Correct order of rate of this reaction for given nucleophile: 
 

• A. F$^-$>PhO$^-$>C$_2$H$_5$O$^-$>I$^-$
• B. C$_2$H$_5$O$^-$>PhO$^-$>I$^-$>F$^-$
• C. I$^-$>C$_2$H$_5$O$^-$>PhO$^-$>F$^-$
• D. PhO$^-$>C$_2$H$_5$O$^-$>F$^-$>I$^-$

Hint:

The nucleophilicity of an ion is influenced by its size and electronegativity. Larger and less electronegative ions tend to be more nucleophilic.

Answer 1

The Correct Option is C

Step 1: Analyze Statement-I.
Bond length is directly proportional to atomic size. If H-X has the longest bond length, X must have the largest atomic size (and thus largest covalent radius) in its group. The statement claims X has the *shortest* radius, which is false.
Step 2: Analyze Statement-II.
In Group 15 hydrides (NH$_3$, PH$_3$, AsH$_3$, SbH$_3$, BiH$_3$): - Boiling point trend: PH$_3$<AsH$_3$<NH$_3$<SbH$_3$<BiH$_3$. The lowest boiling point is for PH$_3$. - Element E is therefore Phosphorus (P). - The maximum covalency of Phosphorus is 5 (due to available d-orbitals, e.g., PCl$_5$), not 4. Thus, the statement is false. Conclusion: Both statements are incorrect.