Match List-I with List-II
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List-I |
List-II |
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(A) Kolbe's reaction |
(I) Preparation of symmetrical and unsymmetrical ethers |
|
(B) Williamson synthesis |
(II) Preparation of Salicylic acid |
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(C) Lucas test |
(III) Organo-Magnesium halide |
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(D) Grignard's reagent |
(IV) Distinction between different types of alcohols |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A)-(II), (B)-(I), (C)-(IV), (D)-(III)
The four names belong to the chemistry of alcohols, phenols and ethers: two are preparations (of salicylic acid and of ethers), one is a test that tells the classes of alcohols apart, and one is a reagent made from an alkyl halide.
(A) Kolbe's reaction — This matches (II) Preparation of Salicylic acid. Sodium phenoxide, more reactive than phenol towards electrophiles, reacts with the weak electrophile carbon dioxide at the ortho position; acidification gives salicylic acid.
\( \displaystyle \ce{C6H5ONa} \xrightarrow[\text{(ii) }\ce{H+}]{\text{(i) }\ce{CO2},\ 400\text{ K},\ 4\text{-}7\text{ atm}} o\text{-}\ce{HOC6H4COOH} \)
(B) Williamson synthesis — This matches (I) Preparation of symmetrical and unsymmetrical ethers. A sodium alkoxide displaces the halide ion from a primary alkyl halide by \( S_N2 \) attack; the two R groups may be the same or different.
\( \displaystyle \ce{R-X + R'-ONa -> R-O-R' + NaX} \)
(C) Lucas test — This matches (IV) Distinction between different types of alcohols. With Lucas reagent (conc. HCl and anhydrous \( \ce{ZnCl2} \)) the alcohol is converted into an insoluble alkyl chloride that makes the solution turbid: at once for a tertiary alcohol, slowly for a secondary alcohol, and not at room temperature for a primary alcohol.
\( \displaystyle \ce{(CH3)3C-OH + HCl} \xrightarrow{\ce{ZnCl2}} \ce{(CH3)3C-Cl + H2O} \)
(D) Grignard's reagent — This matches (III) Organo-Magnesium halide. An alkyl or aryl halide reacts with magnesium in dry ether to give RMgX, in which the C–Mg bond is strongly polar.
\( \displaystyle \ce{R-X + Mg} \xrightarrow{\text{dry ether}} \ce{R-MgX} \)
Shortcut: Kolbe’s reaction gives salicylic acid; (A)-(II) appears only in Option (3).