Which of the following is the weakest acid:
Correct answer: B. Alcohol
- A. Phenol
- B. Alcohol
- C. Carboxylic acid
- D. Water
Explanation
Relative acidic strength of alcohol, phenol, water and carboxylic acid is as follows:Carboxylic Acids>Phenol>Water>Alcohols The acidic strength of a substance depends on the stability of the conjugate base. Stable is the conjugate base, stronger is the acid. The phenoxide ion is very stable because of resonance whereas in case of ethanol, there is no resonance and the +I effect of the ethyl group increase the electron density on the oxygen atom and destabilize the system. So, alcohol is weakest acid and carboxylic acid is the strongest acid.
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About Alcohols and Phenols
Alcohols are classified as primary, secondary or tertiary and studied through their hydrogen bonding, acidity, oxidation and reactions with active metals, acids and halogenating agents. Phenols require separate treatment because the hydroxyl group is attached to an aromatic ring, making their acidity and electrophilic substitution different from ordinary alcohols.
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