Question

In the given reaction sequence conversion of Y to Z is

• A. Wurtz reaction
• B. Wurtz-Fittig reaction
• C. Fittig reaction
• D. Swarts reaction

Hint:

Named Reactions: - Diazotization: Ar-NH\(_2\) + HNO\(_2\) (NaNO\(_2\)/HCl) \( \xrightarrow{0-5^\circ C} \) Ar-N\(_2^+\)Cl\(^-\) (diazonium salt). - Sandmeyer Reaction: Ar-N\(_2^+\)Cl\(^-\) \( \xrightarrow{CuX/HX} \) Ar-X (X=Cl, Br, CN). For Br, use CuBr/HBr or Cu\(_2\)Br\(_2\)/HBr. - Fittig Reaction: 2 Ar-X + 2 Na \( \xrightarrow{\text{dry ether}} \) Ar-Ar + 2 NaX. (Coupling of two aryl halides). - Wurtz Reaction: 2 R-X + 2 Na \( \xrightarrow{\text{dry ether}} \) R-R + 2 NaX. (Coupling of two alkyl halides). - Wurtz-Fittig Reaction: Ar-X + R-X + 2 Na \( \xrightarrow{\text{dry ether}} \) Ar-R + 2 NaX. (Coupling of aryl and alkyl halide).

Answer 1

The Correct Option is C

Let's identify X, Y, and Z.
Step 1: Aniline \( \xrightarrow{\text{NaNO}_2+\text{HCl}, 273-278\text{K}} \) X Aniline (\( \text{C}_6\text{H}_5\text{NH}_2 \)) reacts with nitrous acid (HNO\(_2\), formed in situ from NaNO\(_2\) and HCl) at low temperatures (0-5 \(^\circ\)C or 273-278 K) to form a diazonium salt.
This is diazotization.
X is benzenediazonium chloride, \( \text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- \).
Step 2: X \( \xrightarrow{\text{Cu}_2\text{Br}_2/\text{HBr}} \) Y Benzenediazonium chloride (X) reacts with Cu\(_2\)Br\(_2\)/HBr.
This is the Sandmeyer reaction (or a variation if just Cu/HBr, Gattermann).
It replaces the diazonium group \( -\text{N}_2^+\text{Cl}^- \) with -Br.
Y is bromobenzene, \( \text{C}_6\text{H}_5\text{Br} \).
Step 3: Y \( \xrightarrow{\text{Na, dry ether}} \) Z Bromobenzene (\( \text{C}_6\text{H}_5\text{Br} \)) reacts with sodium (Na) in dry ether.
This is a coupling reaction.
The reaction is \( 2\text{C}_6\text{H}_5\text{Br} + 2\text{Na} \xrightarrow{\text{dry ether}} \text{C}_6\text{H}_5-\text{C}_6\text{H}_5 + 2\text{NaBr} \).
Z is biphenyl (or diphenyl), \( \text{C}_6\text{H}_5-\text{C}_6\text{H}_5 \).
The conversion of Y (\( \text{C}_6\text{H}_5\text{Br} \), an aryl halide) to Z (biphenyl, an aryl-aryl coupled product) using Na in dry ether is known as the Fittig reaction.
Let's review the named reactions in options: - Wurtz reaction: Coupling of two alkyl halides using Na in dry ether to form an alkane (R-X + R'-X + 2Na \( \rightarrow \) R-R' + 2NaX).
- Wurtz-Fittig reaction: Coupling of an alkyl halide and an aryl halide using Na in dry ether to form an alkylarene (R-X + Ar-X + 2Na \( \rightarrow \) R-Ar + 2NaX).
- Fittig reaction: Coupling of two aryl halides using Na in dry ether to form a biaryl (Ar-X + Ar'-X + 2Na \( \rightarrow \) Ar-Ar' + 2NaX).
Here, Y is an aryl halide, and it couples with itself.
- Swarts reaction: Used for the preparation of alkyl fluorides from alkyl chlorides or bromides by heating in the presence of a metallic fluoride (e.
g.
, AgF, Hg\(_2\)F\(_2\), CoF\(_2\), SbF\(_3\)).
The conversion of Y (bromobenzene) to Z (biphenyl) is a Fittig reaction.
This matches option (3).