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Chemistry · Covalent bond fission: Homolytic and heterolytic, free radicals, carbocations and carbanions, stability of carbocations and free radicals, electrophiles and nucleophiles

Arrange in the order of nucleophilicity:

Arrange in the order of nucleophilicity: \( \boldsymbol{H O}^{-}, \boldsymbol{C H}_{3} \boldsymbol{O}^{-}, \boldsymbol{C H}_{3} \equiv \) \( \boldsymbol{C}^{-}, \boldsymbol{C} \boldsymbol{H}_{3} \boldsymbol{C O O}^{-} \)

  • A. \( H O^{-}>C H_{3} O^{-}>C H_{3} \equiv C^{-}>C H_{3} C O O \)
  • B. \( C H_{3} C O O^{-}>H O^{-}>C H_{3} O^{-}>C H_{3} \equiv C^{-} \)
  • C. \( H O^{-}<C H_{3} O^{-}<C H_{3} \equiv C^{-}<C H_{3} C O O^{-} \)
  • D. \( C H_{3} C O O^{-}<H O^{-}<C H_{3} O^{-}<C H_{3} \equiv C^{-} \)

Step-by-step solution

Nucleophilicity generally correlates with basicity, especially in aprotic solvents, but in protic solvents, solvation effects reduce nucleophilicity of small anions. Here, all anions are considered in typical polar protic conditions. Acetylide ion (CH3≡C-) is a strong base (pKa of acetylene ~25) and a carbon nucleophile, making it the most nucleophilic. Methoxide (CH3O-) is more basic and less solvated than hydroxide (HO-) due to its larger size, so it is more nucleophilic. Hydroxide is next. Acetate (CH3COO-) is the weakest base (pKa of acetic acid ~4.76) and least nucleophilic. Thus, the order is: CH3COO- < HO- < CH3O- < CH3≡C-.
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