Asked in PMC Practice Test 36 (2021) 2021Moderate

In the addition of sodium bisulfite to carbonyl system, which of the following is a nucleophile?

Correct answer: B. Sulfite ion

  • A. Sulphide ion
  • B. Sulfite ion
  • C. Hydride ion
  • D. Sodium ion

Explanation

The addition of sodium bisulfite to a carbonyl group takes place as follows:Sodium bisulfite ionizes to form sulfite ions.The sulfite ion acts as a nucleophile, since the sulfur atom is more nucleophilic than oxygen, a C-S bond is formed.Proton is attached to the negatively charged sulfur atom to form a bisulfite addition product.

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About Nucleophilic Addition Reactions

Nucleophilic addition occurs at the polar carbonyl group of aldehydes and ketones, where a nucleophile attacks the electron-deficient carbon atom. Reactions with hydrogen cyanide, sodium bisulfite, alcohols and Grignard reagents are explained through tetrahedral intermediates, acid or base catalysis, and the different reactivity of aldehydes and ketones.

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