Identify the final product [D] in the following sequence: CH3CHO ->[(i) LiAlH4][(ii) H3O+] [A] ->[H2SO4, ] [B] ->[HBr] [C] ->[C6H5Br, Na/dry ether] [D]

Correct answer: (A) (A) Ethylbenzene (C6H5-CH2CH3). LiAlH4 reduces acetaldehyde to ethanol [A]; H2SO4/heat dehydrates it to ethene [B]; HBr adds to give bromoethane [C], CH3CH2Br. The alkyl halide then couples with bromobenzene in the Wurtz-Fittig reaction: CH3CH2Br + C6H5Br + 2Na ->[dry ether] C6H5-CH2CH3 + 2NaBr. The product [D] is ethylbenzene.

NEET 2023 Phase 1 · ChemistryPrevious Year Question

Identify the final product [D] in the following sequence: $CH X_{3} CHO (i) LiAlH X_{4} (ii) H X_{3} O X^{+} [A] H X_{2} SO X_{4}, Δ [B] HBr [C] C X_{6} H X_{5} Br, Na / dry ether [D]$

Answer: (A) (A) Ethylbenzene $(C X_{6} H X_{5} - CH X_{2} CH X_{3})$ . $LiAlH X_{4}$ reduces acetaldehyde to ethanol [A]; $H X_{2} SO X_{4}$ /heat dehydrates it to ethene [B]; HBr adds to give bromoethane [C], $CH X_{3} CH X_{2} Br$ .

A.(A) Ethylbenzene $(C X_{6} H X_{5} - CH X_{2} CH X_{3})$ ✓
B.(B) Biphenyl $(C X_{6} H X_{5} - C X_{6} H X_{5})$
C.(C) $C X_{4} H X_{10}$
D.(D) Sodium acetylide $(HC \equiv C X^{-} Na X^{+})$

Correct Answer

(A) (A) Ethylbenzene $(C X_{6} H X_{5} - CH X_{2} CH X_{3})$

Solution & Explanation

$LiAlH X_{4}$ reduces acetaldehyde to ethanol [A]; $H X_{2} SO X_{4}$ /heat dehydrates it to ethene [B]; HBr adds to give bromoethane [C], $CH X_{3} CH X_{2} Br$ . The alkyl halide then couples with bromobenzene in the Wurtz-Fittig reaction: $CH X_{3} CH X_{2} Br + C X_{6} H X_{5} Br + 2 Na dry ether C X_{6} H X_{5} - CH X_{2} CH X_{3} + 2 NaBr$ . The product [D] is ethylbenzene.

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Identify the final product [D] in the following sequence: CHX3​CHO(i) LiAlHX4​(ii) HX3​OX+​[A]HX2​SOX4​, Δ​[B]HBr​[C]CX6​HX5​Br, Na/dry ether​[D]

Solution & Explanation

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Identify the final product [D] in the following sequence: $CH X_{3} CHO (i) LiAlH X_{4} (ii) H X_{3} O X^{+} [A] H X_{2} SO X_{4}, Δ [B] HBr [C] C X_{6} H X_{5} Br, Na / dry ether [D]$