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JEE Main levelSingle correct optionDifficulty 2 of 3g2194

In water, tert-butyl alcohol (pKa about 18) is a weaker acid than methanol (pKa about 15.5). The best explanation is that

  1. Athe bulky tert-butoxide ion is less well solvated by water than methoxide
  2. Btert-butyl alcohol has no bond
  3. Cmethoxide is less solvated than tert-butoxide
  4. Dthe bond of methanol is longer

Answer: A

Solvation of the alkoxide by hydrogen bonding is the key stabilising factor in water. The small methoxide ion is well solvated, but the bulky tert-butoxide ion has its charge shielded, so it is stabilised less. The alkyl groups also donate electrons. Hence the tertiary alcohol is the weaker acid in water.
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