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14.20 : Esters to Alcohols: Hydride Reductions

Esters are reduced to primary alcohols when treated with a strong reducing agent like lithium aluminum hydride. The reaction requires two equivalents of the reducing agent and proceeds via an aldehyde intermediate.

Lithium aluminum hydride is a source of hydride ions and functions as a nucleophile. The mechanism proceeds in three steps. Firstly, the nucleophilic hydride ion attacks the carbonyl carbon of the ester to form a tetrahedral intermediate. Subsequently, the carbonyl group re-forms, and the alkoxideion departs as the leaving group, generating an aldehyde. Lastly, a second nucleophilic attack by the hydride ion at the carbonyl carbon of the aldehyde yields an alkoxide ion, which gives a primary alcohol as the final product upon protonation.

Figure1

However, in casethe desired product is an aldehyde, it is possible to stop the reaction at the aldehyde intermediate by using a milder reducing agent like diisobutylaluminum hydride or lithium tri(t-butoxy) aluminum hydride,at a lower temperature.

Tags
Ester ReductionHydride ReductionLithium Aluminum HydrideNucleophilic AttackAldehyde IntermediatePrimary AlcoholDiisobutylaluminum HydrideLithium Tri t butoxy Aluminum Hydride

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14.20 : Esters to Alcohols: Hydride Reductions

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14.1 : Carboxylic Acid Derivatives: Overview

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14.2 : Nomenclature of Carboxylic Acid Derivatives: Acid Halides, Esters, and Acid Anhydrides

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14.3 : Nomenclature of Carboxylic Acid Derivatives: Amides and Nitriles

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14.4 : Structures of Carboxylic Acid Derivatives

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14.5 : Physical Properties of Carboxylic Acid Derivatives

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14.6 : Acidity and Basicity of Carboxylic Acid Derivatives

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14.7 : Spectroscopy of Carboxylic Acid Derivatives

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14.8 : Relative Reactivity of Carboxylic Acid Derivatives

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14.9 : Nucleophilic Acyl Substitution of Carboxylic Acid Derivatives

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14.10 : Acid Halides to Carboxylic Acids: Hydrolysis

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14.11 : Acid Halides to Esters: Alcoholysis

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14.12 : Acid Halides to Amides: Aminolysis

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14.13 : Acid Halides to Alcohols: LiAlH<sub>4</sub> Reduction

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14.14 : Acid Halides to Alcohols: Grignard Reaction

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