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🥼organic chemistry review

Secondary Alcohol

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

Definition

A secondary alcohol is an organic compound in which a hydroxyl group (-OH) is attached to a carbon atom that is bonded to two other carbon atoms. This structural feature distinguishes secondary alcohols from primary alcohols, where the hydroxyl group is attached to a carbon atom bonded to only one other carbon, and tertiary alcohols, where the hydroxyl group is attached to a carbon atom bonded to three other carbons.

5 Must Know Facts For Your Next Test

  1. Secondary alcohols can be prepared by the reduction of ketones using reducing agents like sodium borohydride (NaBH4) or lithium aluminum hydride (LiAlH4).
  2. During the nucleophilic addition of Grignard reagents or hydride donors to aldehydes and ketones, secondary alcohols are formed as the product.
  3. Secondary alcohols can be oxidized to ketones using mild oxidizing agents like chromic acid (H2CrO4) or potassium permanganate (KMnO4).
  4. The IUPAC naming system for secondary alcohols involves identifying the longest carbon chain, locating the hydroxyl group, and adding the prefix 'sec-' before the root name.
  5. Secondary alcohols are less reactive than primary alcohols due to the increased steric hindrance around the hydroxyl group, making them more stable.

Review Questions

  • Explain how secondary alcohols can be prepared from carbonyl compounds through reduction reactions.
    • Secondary alcohols can be prepared from the reduction of ketones using reducing agents like sodium borohydride (NaBH4) or lithium aluminum hydride (LiAlH4). In these reactions, the carbonyl carbon of the ketone is attacked by the hydride from the reducing agent, leading to the formation of a secondary alcohol. The hydroxyl group (-OH) is then attached to the carbon that was previously part of the ketone's carbonyl group, resulting in the production of a secondary alcohol.
  • Describe the role of secondary alcohols in the nucleophilic addition reactions of Grignard reagents and hydride donors to aldehydes and ketones.
    • In the nucleophilic addition reactions of Grignard reagents and hydride donors to aldehydes and ketones, secondary alcohols are formed as the product. The nucleophilic carbon of the Grignard reagent or the hydride from the reducing agent attacks the carbonyl carbon of the aldehyde or ketone, leading to the formation of a tetrahedral intermediate. This intermediate then collapses, with the hydroxyl group (-OH) being attached to the carbon that was previously part of the carbonyl group, resulting in the production of a secondary alcohol.
  • Analyze the reactivity and stability of secondary alcohols compared to primary and tertiary alcohols, and explain how this affects their behavior in organic reactions.
    • Secondary alcohols are less reactive than primary alcohols due to the increased steric hindrance around the hydroxyl group, making them more stable. This increased stability is a result of the hydroxyl group being attached to a carbon that is bonded to two other carbon atoms, rather than just one as in primary alcohols. The additional steric hindrance around the hydroxyl group in secondary alcohols makes them less susceptible to nucleophilic attack or oxidation reactions compared to primary alcohols. This difference in reactivity and stability can influence the behavior of secondary alcohols in various organic reactions, such as their resistance to oxidation and their selectivity in reactions involving the addition of nucleophiles to carbonyl compounds.