21.6 Chemistry of Esters
3 min read•may 7, 2024
Esters are versatile compounds that undergo various reactions. They can be hydrolyzed, reduced, or transformed into other functional groups. Understanding these reactions is crucial for synthesizing complex molecules and creating useful products.
Ester reactions involve nucleophilic attacks on the carbonyl carbon. Different reagents lead to different outcomes, from hydrolysis to reduction. These transformations are essential in organic synthesis and have wide-ranging applications in industry and everyday life.
Ester Reactions
Mechanism of ester hydrolysis
Top images from around the web for Mechanism of ester hydrolysis
6.5. Lewis acids & bases, electrophiles & nucleophiles | Organic Chemistry 1: An open textbook View original
Is this image relevant?
organic-chemistry - 環状アセタールの加水分解 View original
Is this image relevant?
organic-chemistry - 環状アセタールの加水分解 View original
Is this image relevant?
6.5. Lewis acids & bases, electrophiles & nucleophiles | Organic Chemistry 1: An open textbook View original
Is this image relevant?
organic-chemistry - 環状アセタールの加水分解 View original
Is this image relevant?
1 of 3
Top images from around the web for Mechanism of ester hydrolysis
6.5. Lewis acids & bases, electrophiles & nucleophiles | Organic Chemistry 1: An open textbook View original
Is this image relevant?
organic-chemistry - 環状アセタールの加水分解 View original
Is this image relevant?
organic-chemistry - 環状アセタールの加水分解 View original
Is this image relevant?
6.5. Lewis acids & bases, electrophiles & nucleophiles | Organic Chemistry 1: An open textbook View original
Is this image relevant?
organic-chemistry - 環状アセタールの加水分解 View original
Is this image relevant?
1 of 3
-
- () acts as a nucleophile attacks the electrophilic carbonyl carbon of the ester ()
- is formed contains a negative charge on the oxygen and a positive charge on the carbonyl carbon
- () acts as a leaving group leaves, forming a ()
- Proton transfer from water to the alkoxide yields an alcohol () and a
- Carboxylate anion is protonated by water to form the carboxylic acid product (acetic acid)
- This process is also known as when applied to the hydrolysis of fats or oils
-
- Protonation of the carbonyl oxygen by a strong acid () activates the ester makes it more susceptible to nucleophilic attack
- Water acts as a nucleophile attacks the electrophilic carbonyl carbon forms a tetrahedral intermediate
- Tetrahedral intermediate is formed contains a positive charge on the carbonyl oxygen and a negative charge on the hydroxyl group
- Alcohol (ethanol) acts as a leaving group leaves, forming a protonated carboxylic acid (acetic acid)
- Deprotonation of the protonated carboxylic acid by water yields the neutral carboxylic acid product (acetic acid)
- This reaction is an example of in reverse
Reduction of esters
- Reduction to primary alcohols using ()
- () from acts as a nucleophile attacks the electrophilic carbonyl carbon of the ester ()
- Tetrahedral intermediate is formed contains a negative charge on the carbonyl oxygen and a positive charge on the aluminum
- Alkoxide () acts as a leaving group leaves, forming an aldehyde ()
- Another hydride from reduces the aldehyde to a primary alcohol () via
- Aqueous workup protonates the alkoxide to yield the primary alcohol product (benzyl alcohol)
- Partial reduction to aldehydes using ()
- Bulky hydride from DIBAL-H selectively reduces the ester () to an aldehyde (benzaldehyde) stops reduction at this stage
- Low temperatures (-78 ℃) and careful control of stoichiometry (1 equivalent of DIBAL-H) prevent over-reduction to the alcohol
- Aqueous workup protonates the aluminum alkoxide to yield the aldehyde product (benzaldehyde)
Ester reactions vs reducing agents
- Reaction with ()
- Nucleophilic addition of the organometallic reagent () to the carbonyl carbon of the ester (ethyl acetate)
- Tetrahedral intermediate is formed contains a negative charge on the carbonyl oxygen and a positive charge on the magnesium
- Alkoxide (ethoxide) acts as a leaving group leaves, forming a ketone ()
- Aqueous workup protonates the magnesium alkoxide to yield a tertiary alcohol ()
- Overall, Grignard reagents convert esters to tertiary alcohols via nucleophilic addition
- Reaction with lithium aluminum hydride ()
- Hydride () from reduces the ester (ethyl acetate) to an aldehyde (acetaldehyde) via nucleophilic addition
- Another hydride from reduces the aldehyde to a primary alcohol (ethanol)
- Aqueous workup protonates the aluminum alkoxide to yield the primary alcohol product (ethanol)
- Overall, converts esters to primary alcohols via sequential reduction steps
Ester Formation and Exchange
- : The process of forming an ester from a carboxylic acid and an alcohol
- : The exchange of the alkoxy group of an ester with another alcohol
- Both reactions involve nucleophilic acyl substitution at the
Key Terms to Review (41)
2-propanol: 2-propanol, also known as isopropyl alcohol or isopropanol, is a colorless, flammable liquid with a characteristic odor. It is an important organic compound that is widely used in various applications, including as a solvent, disinfectant, and in the synthesis of other chemicals.
Acetic Acid: Acetic acid is a weak organic acid with the chemical formula CH3COOH. It is a colorless liquid with a distinctive sour odor and is the main component of vinegar. Acetic acid is a versatile compound that plays important roles in various organic chemistry topics, including functional groups, oxidation of alkenes, reduction of carbonyl compounds, naming of carboxylic acids, and the chemistry of esters.
Acetone: Acetone is a simple organic compound with the chemical formula CH3COCH3. It is a colorless, volatile, flammable liquid that is widely used as a solvent and in various chemical processes. Acetone is a key term that is relevant in the context of several important organic chemistry topics.
Acid-Catalyzed Ester Hydrolysis: Acid-catalyzed ester hydrolysis is a chemical reaction in which an ester compound is broken down into its constituent carboxylic acid and alcohol components in the presence of an acidic catalyst. This process is an important reaction in organic chemistry, particularly in the context of the chemistry of esters.
Alkoxide: An alkoxide is a functional group consisting of an alkyl group (R-) bonded to an oxygen atom (O-). Alkoxides are important intermediates in many organic chemistry reactions, including Grignard reactions, elimination reactions, and carbonyl condensation reactions.
Base-Promoted Ester Hydrolysis: Base-promoted ester hydrolysis is a chemical reaction in which an ester compound is cleaved into its corresponding carboxylic acid and alcohol components through the use of a basic catalyst. This process is an important transformation in organic chemistry, particularly in the context of the chemistry of esters.
Benzaldehyde: Benzaldehyde is an aromatic aldehyde compound with the chemical formula C6H5CHO. It is a colorless liquid with a characteristic almond-like odor and is widely used in the production of various organic compounds, including pharmaceuticals, flavors, and fragrances.
Benzyl Alcohol: Benzyl alcohol is an aromatic alcohol with the chemical formula C6H5CH2OH. It is a clear, colorless liquid with a mild, sweet odor. Benzyl alcohol is an important compound in organic chemistry, with applications in the synthesis of various organic compounds and as a preservative in pharmaceutical and personal care products.
Carbonyl group: A carbonyl group is a functional group characterized by a carbon atom double-bonded to an oxygen atom, represented as C=O. This group is pivotal in organic chemistry as it forms the backbone of various important classes of compounds, influencing their chemical properties and reactivity.
Carboxylate Anion: A carboxylate anion is the negatively charged conjugate base of a carboxylic acid, formed when a carboxylic acid loses a proton. It is a key functional group in organic chemistry that plays an important role in the behavior and reactivity of various organic compounds.
Carboxylic Acid: Carboxylic acids are organic compounds characterized by the presence of a carboxyl functional group (-COOH), which consists of a carbonyl (C=O) and a hydroxyl (-OH) group. They are widely found in nature and play a crucial role in various organic chemistry topics.
Carboxylic acid derivative: Carboxylic acid derivatives are compounds that contain a functional group which is a modified form of the carboxylic acid group (–COOH), where the hydroxyl part (-OH) is replaced by another atom or group of atoms. These derivatives undergo nucleophilic acyl substitution reactions, where an electron-rich nucleophile attacks the carbonyl carbon, leading to the substitution of the leaving group.
DIBAL-H: DIBAL-H, or diisobutylaluminum hydride, is a powerful reducing agent used in organic chemistry to selectively reduce certain functional groups, such as esters and nitriles, to aldehydes and alcohols, respectively. It is a valuable tool in the preparation of aldehydes and ketones, as well as in the chemistry of esters.
Diisobutylaluminum Hydride: Diisobutylaluminum hydride (DIBAL-H) is a reducing agent commonly used in organic chemistry for the selective reduction of esters, nitriles, and halides to aldehydes or alcohols. It is a powerful, yet mild reducing agent that can be used to transform various functional groups without affecting others.
Ester Hydrolysis: Ester hydrolysis is the chemical reaction in which an ester compound is broken down into its constituent alcohol and carboxylic acid components through the addition of water. This process is an important reaction in organic chemistry, particularly in the context of the chemistry of esters.
Esterification: Esterification is a chemical reaction that involves the formation of an ester compound from the reaction between a carboxylic acid and an alcohol. This process is crucial in various areas of organic chemistry, including the properties of functional groups, polar reactions, the behavior of alcohols and phenols, the reactions of carboxylic acids, the chemistry of esters, and the reactions of monosaccharides.
Ethanol: Ethanol, also known as ethyl alcohol, is a colorless, volatile, and flammable liquid that is the principal type of alcohol found in alcoholic beverages. It is an important organic compound with diverse applications in various fields, including as a fuel, solvent, and chemical feedstock.
Ethoxide: Ethoxide is a functional group consisting of an ethyl group (CH3CH2-) bonded to an oxygen atom. It is an important intermediate in various organic reactions, particularly in the context of E2 reactions, ester chemistry, and Claisen condensations.
Ethyl Acetate: Ethyl acetate is a versatile organic compound that serves as a common solvent, a flavoring agent, and an important intermediate in various chemical reactions. It is the ester formed by the reaction between acetic acid and ethanol, and its diverse applications make it a crucial compound in both laboratory and industrial settings.
Ethyl Benzoate: Ethyl benzoate is an ester compound formed by the reaction between benzoic acid and ethanol. It is a colorless, aromatic liquid with a sweet, fruity odor, commonly used as a flavoring agent and in the synthesis of other organic compounds.
Fischer Esterification: Fischer esterification is a chemical reaction that involves the formation of an ester compound from a carboxylic acid and an alcohol, typically in the presence of an acid catalyst. This reaction is a key process in the synthesis and interconversion of various organic compounds, particularly esters, which have a wide range of applications in the fields of chemistry, biology, and industry.
Fischer esterification reaction: A Fischer esterification reaction is a chemical process where a carboxylic acid reacts with an alcohol in the presence of an acid catalyst to form an ester and water. It is an equilibrium process that is often driven to completion by removing the water formed during the reaction.
Grignard Reagents: Grignard reagents are a class of highly reactive organometallic compounds that are widely used in organic synthesis. They are formed by the reaction of an alkyl or aryl halide with magnesium metal and play a crucial role in various organic transformations.
Grignard reagents (RMgX): Grignard reagents are organomagnesium compounds formed by the reaction of an alkyl or aryl halide with magnesium metal in dry ether. They act as nucleophiles that can form carbon-carbon bonds, making them valuable tools in organic synthesis.
HCl: HCl, or hydrochloric acid, is a strong, corrosive acid that plays a crucial role in various chemical processes and reactions. It is composed of hydrogen (H) and chlorine (Cl) atoms, and its unique properties make it an important component in numerous organic chemistry topics, including acid-base chemistry, electrophilic additions, alcohol reactions, ester chemistry, and peptide sequencing.
Hydride: A hydride is a compound in which hydrogen is bonded to a more electropositive element, such as a metal or a metalloid. Hydrides play a crucial role in various organic chemistry reactions, including the hydration of alkenes, the oxidation of alcohols, the nucleophilic addition of hydrides and Grignard reagents, and the chemistry of esters.
Hydride shift: A hydride shift is a rearrangement process where a hydrogen atom with its pair of electrons moves from one carbon to an adjacent carbocation center, stabilizing the molecule during electrophilic additions. This mechanism is key in understanding how carbocations can rearrange to form more stable intermediates in reactions involving alkenes.
Hydroxide Ion: The hydroxide ion (OH-) is a negatively charged species consisting of one oxygen atom and one hydrogen atom. It is an important chemical species that plays a crucial role in various organic chemistry reactions, particularly in the context of nucleophilic addition of water (hydration) and the chemistry of esters.
Lactones: Lactones are cyclic organic compounds formed by the intramolecular esterification of hydroxycarboxylic acids. They are a specific type of ester found within the broader context of carboxylic acid derivatives and nucleophilic acyl substitution reactions.
LiAlH4: LiAlH4, also known as lithium aluminum hydride, is a powerful reducing agent commonly used in organic chemistry reactions. It is particularly useful in the context of nucleophilic addition reactions of aldehydes and ketones, the chemistry of esters and amides, as well as the synthesis of amines.
Lithium Aluminum Hydride: Lithium aluminum hydride (LiAlH4) is a powerful reducing agent used in organic chemistry for the selective reduction of various functional groups. It is a white, crystalline solid that reacts violently with water and other protic solvents, making it an important reagent in many synthetic transformations.
Methoxide: Methoxide is the conjugate base of methanol, formed by the removal of a proton from the hydroxyl group. It is a powerful nucleophile and base that plays a crucial role in the chemistry of esters.
Methyl Benzoate: Methyl benzoate is an organic compound that consists of a benzene ring with a carboxyl group (-COOH) attached, and a methyl group (-CH3) esterified to the carboxyl group. It is a colorless liquid with a sweet, fruity odor and is commonly used as a flavoring agent and in the production of various chemical compounds.
Methylmagnesium bromide: Methylmagnesium bromide, also known as Grignard reagent, is an organometallic compound that is widely used in organic chemistry for the formation of carbon-carbon bonds through nucleophilic addition reactions. It is a key reagent in various transformations, including the hydration of aldehydes and ketones, the conjugate addition to α,β-unsaturated carbonyl compounds, and the synthesis of esters.
Nucleophilic Addition: Nucleophilic addition is a fundamental organic reaction in which a nucleophile, a species that donates electrons, adds to an electrophilic carbon center, typically a carbonyl carbon, to form a new product. This reaction is central to understanding many important topics in organic chemistry, including functional groups, polar reactions, carbocation stability, reaction stereochemistry, and the chemistry of aldehydes, ketones, alcohols, and other carbonyl-containing compounds.
Nucleophilic addition reaction: A nucleophilic addition reaction is a chemical process where a nucleophile forms a bond with an electrophilic carbon atom of a compound, typically found in aldehydes and ketones. This reaction results in the conversion of the carbonyl group into a more complex, often larger, molecule.
Reduction of Esters: The reduction of esters is a chemical reaction that converts ester functional groups into alcohol functional groups. This process is important in organic chemistry as it allows for the transformation of ester compounds into other useful molecules.
RMgX: RMgX, also known as a Grignard reagent, is an organometallic compound consisting of an alkyl or aryl group (R) bonded to a magnesium atom (Mg) and a halide (X). These versatile reagents are widely used in organic synthesis for the formation of new carbon-carbon bonds and the addition of nucleophiles to carbonyl groups, leading to the synthesis of alcohols.
Saponification: Saponification is a chemical reaction that occurs when an ester, such as a fat or oil, is heated with a strong base like sodium hydroxide or potassium hydroxide. This process results in the formation of a salt of a fatty acid, which is the main component of soap.
Tetrahedral Intermediate: A tetrahedral intermediate is a key reaction step that occurs in many organic chemistry reactions, where a trigonal planar carbonyl carbon temporarily becomes a tetrahedral carbon with four bonded atoms. This transient intermediate is crucial for understanding the mechanisms of various nucleophilic addition and substitution reactions.
Transesterification: Transesterification is a chemical reaction in which an ester is transformed into another ester through the interchange of the alkoxy moiety. This process is of great importance in the context of organic chemistry, particularly in the areas of functional groups, nucleophilic acyl substitution reactions, and the chemistry of esters.