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🥼organic chemistry review

Mandelonitrile

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Mandelonitrile is a cyanohydrin, a type of organic compound formed by the addition of hydrogen cyanide (HCN) to an aldehyde or ketone. It is specifically the cyanohydrin derived from benzaldehyde, and is an important intermediate in organic synthesis.

5 Must Know Facts For Your Next Test

  1. Mandelonitrile is formed via the nucleophilic addition of hydrogen cyanide (HCN) to benzaldehyde, a process known as cyanohydrin formation.
  2. The reaction is reversible, and mandelonitrile can be hydrolyzed to regenerate benzaldehyde and hydrogen cyanide.
  3. Mandelonitrile is a useful synthetic intermediate, as the nitrile group can be converted to other functional groups like carboxylic acids or primary amines.
  4. Mandelonitrile is found naturally in some plants, such as almonds, where it serves as a defense mechanism against herbivores.
  5. The stereochemistry of mandelonitrile is important, as the $\text{R}$-enantiomer is the naturally occurring form and has different properties than the $\text{S}$-enantiomer.

Review Questions

  • Describe the mechanism of the nucleophilic addition reaction that forms mandelonitrile from benzaldehyde and hydrogen cyanide.
    • The formation of mandelonitrile from benzaldehyde and hydrogen cyanide proceeds via a nucleophilic addition mechanism. First, the carbonyl carbon of benzaldehyde is electrophilically attacked by the nucleophilic cyanide ion, forming a tetrahedral intermediate. This intermediate then collapses, expelling water and leaving the cyanide group attached to the benzaldehyde carbon, resulting in the cyanohydrin product, mandelonitrile.
  • Explain the significance of the stereochemistry of mandelonitrile and how it relates to its natural occurrence and synthetic applications.
    • Mandelonitrile exists as two enantiomers, the $\text{R}$-enantiomer and the $\text{S}$-enantiomer. The $\text{R}$-enantiomer is the naturally occurring form found in plants like almonds, where it serves as a defense mechanism. The two enantiomers have different physical and chemical properties, which is important in synthetic applications. For example, the $\text{R}$-enantiomer may be preferred for certain reactions or pharmaceutical applications, requiring the use of stereoselective synthesis techniques to obtain the desired stereoisomer.
  • Discuss the versatility of mandelonitrile as a synthetic intermediate and the types of transformations that can be performed on the nitrile group to access other functional groups.
    • Mandelonitrile is a valuable synthetic intermediate due to the reactivity of the nitrile group. The nitrile can be converted to a variety of other functional groups, such as carboxylic acids, primary amines, or even more complex molecules. For example, the nitrile can be hydrolyzed to a carboxylic acid, reduced to a primary amine, or used in nucleophilic addition reactions to form more complex structures. This versatility makes mandelonitrile a useful building block in organic synthesis, allowing for the construction of a wide range of compounds from this common starting material.