InterviewSolution
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InterviewSolution
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Which of the following statements is/ are true? (I) Ethers are soluble in cone. H_2SO_4 but separate out on addition of water. (II) Ethers are used as solvents for BF_3 and Grignard reagent. (III) Mononitration of p-methylanisolc gives 2-nitro-4-methylanisole (IV) Monobromination ofp-ethoxyphenol gives 2-bromo-4-ethoxyphenol (V) 4-ChlorophenoI (I) will dissolve in NaOH but 4-chloro-1 -methyl benzene (II) will not. (VI) 4-Methyl benzoic (111) acid will dissolve in aq. NaHCO_(3) , but 4-methyl phenol (IV) will not. (VII) 2,4,6-Trinilrophenol (V) will dissolve in aq. NaHCO_(3)but 4-methyl phenol (VI) will not. (VIII) 4-Ethyl phenol (VII) will dissolve in aq. NaOH but ethyl phenyl ether (VI11) will not. |
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Answer» `underset("Acid"_(1))([R_(2)OH])^(+) + underset("Base"_(2))(H_(2)O) to underset("Base"_(1))(R_(2)O) + underset("Acid"_(2))(H_(3)O^(+))` (II) Due to unshared electron pairs, ETHERS act as Lewis bases and hence easily react with Lewis acids like `BF_3` and RMgBr to form coordinated COMPOUNDS. `(C_(2)H_(5))_(2) OVERSET(..)o + BF_(3) to (C_(2)H_(5))_(2) overset(..)o : overset(+)(BF_(3)) 2(C_(2)H_(5))_(2)overset(..)O: + RMgBr to (C_(2)H_(5))_(2)O to underset(Br)overset(R)(Mg) larr O(C_(2)H_(5))_(2)` Note that two molecules of ether coordinate tetrahedrally with one `Mg^(2+)` (III)  (IV)  (V) Due to -I effect of Cl, 4-chlorophenol is acidic and dissolves in NaOH, but (II) is an aryl halide and does not dissolve. (VI) (III) is an acid and dissolves in `NaHCO_3` but (IV) is a phenol and does not dissolve. (VII) Although (V) is a phenol, because of the presence of `(3NO_2)` group, it is exceptionally acidic (pKa=0.38). So it dissolves in `NaHCO_3`, but (VI) is a phenol (pKa= 10.17) and will not dissolve. (VIII) (VII) is a phenol and dissolves in NaOH, but (VIII) is an ether, and does not dissolve. |
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