select the strongest pair OCH NO CF, 21.14 Without consulting tables, select the

Question

select the strongest pair

OCH NO CF, 21.14 Without consulting tables, select the stronger from each of the following pair acid (a) 4-Methyl phenol and 4-fluorophenol (c) 4-Nitrophenol and 3-nitrophenol (b) 4-Methylphenol and 4-nitrophenol (d) 4-Methylphenol and benzyl alcoho 21.15 What products would be obtained from each of the following acid-base reactio (a) Sodium ethoxide in ethanol phenol c) Sodium phenoxide t aqueous hy (b) Phenol aqueous sodium hydroxide (d) Sodium phenoxide t H20 co 21.16 Describe a simple chemical test that could be used to distinguish between me c) 4-Methylphenol, and 2,4 (a) 4-Chlorophenol and 4-chloro-1-methylbenzene (d) Ethyl phenyl ether and b) 4-Methyl phenol and 4-methylbenzoic acid

Explanation / Answer

a) 4-Flurophenol is more acidic than phenol, due the negative inductive effect (I) of fluorine, that reduces the negative charge, located on the oxygen of the phenolate anion.

And, 4-methylphenol, the methyl group yields a positive inductive effect (+I), thus increasing the negative charge on phenolate oxygen. That's why is is less acidic than phenol.

Thus, in the pair, 4-Flurophenol is more acidic then 4-methylphenol.

b) 4-nitrophenol is more acidic than phenol, because due to resonance (-R effect of NO2 group) negative charge can be delocalized on ring and nitro group (strong electron withdrawing group). It stabilizes the negative charge on phenolate oxygen.

And, 4-methylphenol, the methyl group yields a positive inductive effect (+I), thus increasing the negative charge on phenolate oxygen. That's why is is less acidic than phenol.

Thus, in the pair, 4-nitrophenol is more acidic then 4-methylphenol.

C) 4-nitrophenol is more acidic than phenol, because due to resonance (-R effect of NO2 group) negative charge can be delocalized on ring and nitro group (strong electron withdrawing group). It stabilizes the negative charge on phenolate oxygen.

Whereas, in case of 3-nitrophenol the absence of resonance stabilization of negative charge on on phenolate oxygen makes it less acidic then 4-nitrophenol.

d) 4-methylphenol, the methyl group yields a positive inductive effect (+I), thus increasing the negative charge on phenolate oxygen. That's why is is less acidic than phenol, but it is acidic in nature.

Whereas, in benzyl alcohol there is no phenolic OH group. Hence, it is way less acidic then even phenol.

Thus, in the pair, 4-methylphenol is more acidic then benzyl alcohol.

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