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Questions and Answers
What is the main limitation of using Grignard reagents with acid chlorides?
What is the main limitation of using Grignard reagents with acid chlorides?
Friedel-Crafts acylation is an example of nucleophilic addition.
Friedel-Crafts acylation is an example of nucleophilic addition.
False
In the reaction between alkenes and acid chlorides, what type of addition is illustrated?
In the reaction between alkenes and acid chlorides, what type of addition is illustrated?
Markovnikov's addition
The main product of the Friedel-Crafts acylation reaction is an __________ ketone.
The main product of the Friedel-Crafts acylation reaction is an __________ ketone.
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Match the following reaction types with their descriptions:
Match the following reaction types with their descriptions:
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Which of the following compounds is most reactive towards nucleophilic addition?
Which of the following compounds is most reactive towards nucleophilic addition?
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Aldehydes can react to form acetals through a mechanism involving hemiacetals.
Aldehydes can react to form acetals through a mechanism involving hemiacetals.
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What is formed when a Grignard reagent reacts with a carbonyl compound?
What is formed when a Grignard reagent reacts with a carbonyl compound?
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The product formed by the reaction of an aldehyde with a primary amine is called a __________.
The product formed by the reaction of an aldehyde with a primary amine is called a __________.
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Which reagent can be used to add to a carbonyl group to form an alcohol?
Which reagent can be used to add to a carbonyl group to form an alcohol?
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Match the following reactions with their respective products:
Match the following reactions with their respective products:
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Ketones are more reactive than aldehydes in nucleophilic addition reactions.
Ketones are more reactive than aldehydes in nucleophilic addition reactions.
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What type of compounds do aldehydes react with to form hemiacetals?
What type of compounds do aldehydes react with to form hemiacetals?
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Which reaction is also known as the Etard reaction?
Which reaction is also known as the Etard reaction?
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Grignard reagents cannot be used to prepare ketones.
Grignard reagents cannot be used to prepare ketones.
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Name the reaction that involves the formation of an aldehyde from a gem-diacetate.
Name the reaction that involves the formation of an aldehyde from a gem-diacetate.
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The reaction known for preparing aldehydes from toluene is called the ______.
The reaction known for preparing aldehydes from toluene is called the ______.
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Match the following reactions with their corresponding process:
Match the following reactions with their corresponding process:
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What type of product is formed when Grignard reagents react with acid chlorides?
What type of product is formed when Grignard reagents react with acid chlorides?
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The Cannizzaro reaction involves the addition of a Grignard reagent to a ketone.
The Cannizzaro reaction involves the addition of a Grignard reagent to a ketone.
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What is produced when 2R—C—Cl is reacted with dry ether?
What is produced when 2R—C—Cl is reacted with dry ether?
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Study Notes
Reactivity of Carbonyl Compounds
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The reactivity of carbonyl compounds towards nucleophilic addition reactions decreases with increasing steric hindrance and electron-donating ability of the substituents.
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This is reflected in the following order of reactivity:
- Aldehydes are more reactive than ketones due to the presence of only one alkyl group, making the carbonyl carbon more electrophilic.
- Formaldehyde (HCHO), with no alkyl groups, is the most reactive aldehyde.
- As the size of the alkyl group increases, the steric hindrance around the carbonyl carbon increases, decreasing its reactivity.
- Branched aldehydes are less reactive than their linear counterparts due to steric hindrance.
- Ketones are less reactive than aldehydes due to the presence of two alkyl groups.
- Bulkier ketones are less reactive than smaller ketones.
Nucleophilic Addition Reactions
- Nucleophilic addition reactions involve the attack of a nucleophile on the electrophilic carbonyl carbon.
- The carbonyl carbon is electrophilic due to the polarization of the carbonyl group, with the oxygen atom being more electronegative.
- The nucleophile attacks the carbonyl carbon from a direction perpendicular to the plane of the sp2-hybridized orbitals of the carbonyl carbon.
Examples of Nucleophilic Addition Reactions
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Acetal and Ketal Formation: Aldehydes and ketones react with alcohols in the presence of an acid catalyst to form hemiacetals and hemiketals, respectively. These intermediates then react with another molecule of alcohol to form acetals and ketals.
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Addition of Grignard Reagents: Grignard reagents (RMgX) are strong nucleophiles that react with carbonyl compounds to form alcohols.
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Addition of Sodium Bisulfite: Sodium bisulfite (NaHSO3) adds to aldehydes to form crystalline bisulfite addition products.
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Addition of Hydrogen Cyanide (HCN): HCN adds to carbonyl compounds to form cyanohydrins.
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Addition of Ammonia Derivatives: Ammonia and its derivatives react with carbonyl compounds to form imines and enamines.
Formation of Ketones
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From Organometallics: Ketones can be prepared by the reaction of two equivalents of an organometallic reagent, such as dialkyl cadmium, with an acid chloride.
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From Grignard Reagents and Acid Chlorides: Ketones can also be prepared by the reaction of a Grignard reagent with an acid chloride.
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From Nitriles: Ketones can be synthesized by the reaction of a nitrile with a Grignard reagent.
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