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Saturday, September 12, 2020

Alcohols and Phenols both are acidic but phenols are more acidic. Why?

(1)  alcohols fails to turn blue litmus red while phenol do so.

(2) alcohols fails to neutralize alkalies whereas phenols do so:

(3) Both phenol and phenoxide ions exhibit resonance, whereas alcohols and alkoxide ion do not.

(4) Due to resonance, positive charge 's developed over "O"of phenol, this weakens O-H bond and facilitates release of a proton. On the other hand. due to electron donating nature of alkyl group. -O-H bond is strengthened. therefore. it hinders the release of proton.      

(5) The phenoxide ion is more stable than phenol, due to o greater dispersal of  negative charge, therefore. equilibrium get shifted to forward direction. whereas alkoxide ion is less stable than alcohols due to intensification of negative charge, so equilibrium get shifted towards backward direcrion. Due to these fact it is clear that phenols are more acidic than alcohols. 

Related Questions:

(1) Benzamide is less easily hydrolysed than methyl benzoate. Why ?

(2) Highly branched carboxylic acids are less acidic than unbranched acids. Explain why?

(3) Phenoxide ion is more stable than an alkaoxide. why?

(4) What is Steric Inhibition of Deprotonation effect ? Or SID effect ?

(5) What is the ortho effect? Why are nearly all ortho substitute benzoic acids (except some groups) stronger acid than benzoic acid?

(6) Why is o-toluic acid (2-methyl benzoic acid) stronger than benzoic acid ?

(7) Which is more acidic 2-methyl benzoic acid , 3-methyl benzoic acid or 4-methyl benzoic acid.?

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