20.7 Synthesis and Reactions of Acid Anhydrides | Organic Chemistry
TLDRThis video script provides a comprehensive review of the synthesis and reactions of acid anhydrides, a key topic in organic chemistry. The primary method for synthesizing an acid anhydride involves starting with an acid halide and replacing the halide with a carboxyl group using an appropriate carboxylic acid. The anhydride can be converted into less reactive carboxylic acid derivatives, such as esters, amides, and carboxylic acids or carboxylates. The reactions with organometallics like Grignard reagents or organocuprates are analogous to those with acyl halides, where one equivalent of Grignard reagent can substitute a methyl group, but excess can lead to further reactions. Hydrogenation reactions with acid anhydrides are also discussed, highlighting the use of lithium aluminum hydride or sodium borohydride to reduce the anhydride to an alcohol, with the option to stop at an aldehyde using lithium tri-tert-butoxy aluminum hydride. The script emphasizes the similarities between the reactions of acid anhydrides and acyl halides, offering a clear understanding of the subject. The video is part of an organic chemistry playlist released weekly throughout the school year, with additional resources available on chadsprep.com for further study and practice.
Takeaways
- π¬ The primary method to synthesize an acid anhydride is by starting with a more reactive acid halide and adding an appropriate carboxylic acid to replace the halide with a carboxyl group.
- π Acid anhydrides can undergo nucleophilic acyl substitution, leading to conversion into less reactive carboxylic acid derivatives such as esters, amides, carboxylic acids, and carboxylate ions.
- βοΈ Acid anhydrides can be converted into esters using an appropriate alcohol, either uncatalyzed or base-catalyzed with an alkoxide ion.
- π§ͺ The corresponding amide can be formed uncatalyzed by using an appropriate amine or base-catalyzed with an amide ion.
- π§ Carboxylic acid can be produced from an anhydride using water, while a carboxylate can be formed using hydroxide.
- π Reactions of an acid anhydride with organometallics like Grignard reagents or organocuprates are similar to those with acyl halides.
- βοΈ Excess Grignard reagent can lead to further reactions with ketones, producing tertiary alcohols, but using one equivalent with a Gilman reagent stops the reaction at the desired product.
- β Lithium dialkylcuprate (Gilman reagent) prevents further reaction with ketones, allowing for the formation of the desired product without overreaction.
- πΆ Hydride reductions with lithium aluminum hydride or sodium borohydride can reduce anhydrides to alcohols, but lithium aluminum hydride can also reduce aldehydes further.
- βοΈ To stop the reduction at the aldehyde stage, a special reducing agent, lithium tri-tert-butoxy aluminum hydride, should be used at low temperatures.
- π The reactions of acid anhydrides are nearly identical to those of acyl halides, and understanding one set helps in understanding the other.
- π For further study and practice, the instructor recommends checking out the premium course on chadsprep.com for additional resources and rapid reviews.
Q & A
What is the primary method for synthesizing an acid anhydride?
-The primary method for synthesizing an acid anhydride is to start with an acid halide and then add the appropriate carboxylic acid to replace the halide with a carboxyl group. This can be done either uncatalyzed with the carboxylic acid or base catalyzed with an appropriate carboxylate.
Which carboxylic acid derivatives can an acid anhydride be converted into?
-An acid anhydride can be converted into carboxylic acids, esters, amides, and carboxylates. However, it cannot be directly turned into an acid chloride.
How can an acid anhydride be converted into an ester?
-An acid anhydride can be converted into an ester through an uncatalyzed reaction with an appropriate alcohol, or a base-catalyzed reaction with an appropriate alkoxide ion.
What is the role of a Grignard reagent in the reaction with an acid anhydride?
-A Grignard reagent can substitute a methyl group for the carboxyl leaving group in an acid anhydride. However, Grignard reagents can also react with ketones, so if used in excess, they can continue to react and produce a tertiary alcohol. To avoid this and stop at the substitution, a Gilman reagent (lithium dialkylcuprate) can be used.
How does the reaction of an acid anhydride with organometallics like Grignard or organocuprates differ from the reaction with acyl halides?
-The reactions of an acid anhydride with organometallics like Grignard or organocuprates are essentially analogous to what is seen with acyl halides. Both types of reactions involve nucleophilic acyl substitution.
What are the possible outcomes when an acid anhydride reacts with lithium aluminum hydride?
-When an acid anhydride reacts with lithium aluminum hydride, the initial reaction replaces the leaving group with a hydrogen to form an aldehyde. However, lithium aluminum hydride can further reduce the aldehyde to form an alcohol.
How can the reduction of an acid anhydride to an aldehyde be stopped at the aldehyde stage?
-To stop the reduction at the aldehyde stage, a special reducing agent, lithium tri-tert-butoxy aluminum hydride, should be used, and the reaction should be carried out at low temperatures.
What is the significance of the nucleophilic acyl substitution in the context of carboxylic acid derivatives?
-Nucleophilic acyl substitution is a key reaction type that allows for the conversion between different carboxylic acid derivatives, such as from an acid anhydride to an ester, amide, or carboxylic acid, and is fundamental to organic synthesis.
Why are acid-catalyzed reactions generally not performed with acid chlorides and anhydrides?
-Acid-catalyzed reactions with acid chlorides and anhydrides are generally not performed because these compounds are already highly reactive. The use of additional acid can lead to unwanted side reactions or over-catalysis.
What is the purpose of the bell notification subscription mentioned in the script?
-The bell notification subscription is a feature on the video platform that allows viewers to receive alerts whenever new content is posted by the channel. In this context, it ensures that students are notified of new lessons in the organic chemistry playlist.
Where can one find practice problems and a study guide for carboxylic acids and their derivatives?
-Practice problems and a study guide for carboxylic acids and their derivatives can be found in the premium course offered on chadsprep.com.
What is theζζΊη©εε¦ (organic chemistry) playlist mentioned in the script?
-TheζζΊεε¦ (organic chemistry) playlist is a collection of educational videos released weekly throughout the school year, focusing on various topics in organic chemistry, including the synthesis and reactions of acid anhydrides and other carboxylic acid derivatives.
Outlines
π Synthesis and Reactions of Acid Anhydrides
This paragraph discusses the synthesis and various reactions of acid anhydrides. It begins with a review of the conversion process from carboxylic acid derivatives, emphasizing the primary method of synthesizing an acid anhydride from an acid halide. The paragraph also covers several reactions, including inner conversion, nucleophilic acyl substitution, and reactions with organometallics and hydride reduction. The lesson is part of an organic chemistry series released weekly throughout the school year, and viewers are encouraged to subscribe for updates. The summary touches on the conversion of anhydrides into less reactive carboxylic acid derivatives, such as esters, amides, and carboxylic acids or carboxylates. It also explains the reactions of anhydrides with organometallics like Grignard reagents and organocuprates, and the use of hydride reducing agents like lithium aluminum hydride and sodium borohydride, including how to selectively stop reactions at the aldehyde stage.
Mindmap
Keywords
π‘Acid anhydrides
π‘Nucleophilic acyl substitution
π‘Organometallics
π‘Hydride reduction
π‘Acid halides
π‘Esterification
π‘Amide formation
π‘Carboxylic acids
π‘Carboxylates
π‘Grignard reagent
π‘Lithium dialkylcuprate
Highlights
The only real way to synthesize an acid anhydride is by starting with a more reactive acid halide and adding the appropriate carboxylic acid to replace the halide with a carboxyl group.
Acid anhydrides can be synthesized either uncatalyzed with the carboxylic acid or base catalyzed with an appropriate carboxylate.
Acid catalyzed reactions generally aren't done with acid chlorides and anhydrides, but theoretically, they would still produce the anhydride.
Anhydrides can be converted into less reactive carboxylic acid derivatives, such as esters, amides, carboxylic acids, and carboxylates.
Esters are formed by an uncatalyzed conversion of anhydrides using the appropriate alcohol.
Amides are made by an uncatalyzed reaction with the appropriate amine, or base catalyzed with the appropriate amide ion.
Carboxylic acids are produced by reacting anhydrides with water, and theoretically, acid catalysis could also be used.
Carboxylates are formed by using hydroxide to react with anhydrides, similar to reactions with acyl chlorides.
Reactions of an acid anhydride with organometallics like Grignard reagents or organocuprates are analogous to those with acyl halides.
Excess Grignard reagent will substitute a methyl group for the carboxyl leaving group in an anhydride, but it will continue to react with ketones if present.
To stop the reaction at one equivalent, use the Gilman reagent, lithium dialkyl cuprate, which won't react with the subsequent ketone produced.
Hyride reductions of acid anhydrides are similar to those with acyl halides, using lithium aluminum hydride or sodium borohydride.
Lithium aluminum hydride can reduce the leaving group of an anhydride to produce an aldehyde, but it will continue to react to form an alcohol.
To stop at the aldehyde stage, use a special reducing agent, lithium tri-tert-butoxy aluminum hydride, at low temperatures.
The reactions of acid anhydrides with organometallics and hydride reductions are nearly identical to those of acyl halides.
The lesson is part of an organic chemistry playlist released weekly throughout the school year.
Subscribers to the channel will be notified every time a new lesson is posted.
The study guide and practice problems for carboxylic acids and their derivatives are available in the premium course on Chad's website.
New organic chemistry 2 final exam rapid reviews are being released as part of the premium course on Chad's website.
Transcripts
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