Which of the following is least acidic?a)o-Cresolb)p-Chlorophenolc)Phenold)p-NitrophenolCorrect answer is option 'A'. Can you explain this answer?

Question

Answer

>>Carboxylic acids have more acidic strength than alcohols and phenols because they reacts  even with weak bases to form salts. >>Order of acidic strength of carboxylic acids increases with increase in electron with drawing Group(-halogens,-NO2,-CHO,-COOH).->>So, Order of acidic strength is 'd>b>c>a'

Answer

Option is a
because due to +I inductive effect of c2h5.
acidic strength is inversely proportional to +I inductive effect

Answer

o-cresol (o−(CH3)C6H4−(OH)) is least acidic. −OH group and CH3 groups are electron releasing group. It increases the electron density on a benzene ring and does not delocalize the negative charge of phenoxide ion.

Hence, it decreases the acidity of phenol. −Cl and −NO2 groups are electron-withdrawing groups. They delocalize the electron density of phenoxide ion. It increases the acidity of phenol.

Answer

Explanation:

To determine the acidity of the given compounds, we need to consider the stability of the corresponding conjugate bases. The more stable the conjugate base, the stronger the acid. The stability of the conjugate base can be influenced by various factors including electron-donating or electron-withdrawing groups.

p-Nitrophenol (d):
- The presence of the electron-withdrawing nitro group (-NO2) makes the conjugate base more stable due to resonance effects.
- The negative charge on the oxygen atom can be delocalized onto the nitro group, leading to increased stability.
- Therefore, p-Nitrophenol is the most acidic compound among the given options.

Phenol (c):
- The -OH group in phenol is a weakly acidic group.
- The conjugate base of phenol is stabilized by resonance, where the negative charge is delocalized onto the benzene ring.
- The presence of the benzene ring also provides electron-donating effects, which further stabilize the conjugate base.
- Hence, phenol is more acidic than p-chlorophenol and o-cresol.

p-Chlorophenol (b):
- The chlorine atom in p-chlorophenol is electron-withdrawing.
- The presence of the chlorine atom increases the electron density on the oxygen atom, making the conjugate base less stable.
- Therefore, p-chlorophenol is less acidic than phenol.

o-Cresol (a):
- o-Cresol has a methyl group (-CH3) as a substituent on the benzene ring.
- The methyl group is electron-donating, which destabilizes the negative charge on the oxygen atom.
- The presence of the methyl group decreases the electron density on the oxygen atom, making the conjugate base less stable.
- Therefore, o-cresol is the least acidic compound among the given options.

In Summary:
- p-Nitrophenol is the most acidic compound.
- Phenol is more acidic than p-chlorophenol and o-cresol.
- o-Cresol is the least acidic compound among the given options.

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