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Questions and Answers
What is the method used to prepare aldehydes from acyl chlorides?
What is the method used to prepare aldehydes from acyl chlorides?
Which reagent is specifically used in the Stephen reaction to convert nitriles to aldehydes?
Which reagent is specifically used in the Stephen reaction to convert nitriles to aldehydes?
Which of the following methods employs chromyl chloride to prepare aldehydes?
Which of the following methods employs chromyl chloride to prepare aldehydes?
What is the resulting product when nitriles are reduced by DIBAL-H?
What is the resulting product when nitriles are reduced by DIBAL-H?
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What type of compounds are obtained through the Gatterman-Koch reaction?
What type of compounds are obtained through the Gatterman-Koch reaction?
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When toluene undergoes side chain chlorination followed by hydrolysis, what is the final product?
When toluene undergoes side chain chlorination followed by hydrolysis, what is the final product?
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Which reaction is used to prepare ketones from acyl chlorides?
Which reaction is used to prepare ketones from acyl chlorides?
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What kind of aldehydes are prepared through the oxidation of aromatic hydrocarbons?
What kind of aldehydes are prepared through the oxidation of aromatic hydrocarbons?
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What is the key outcome of the Rosenmund reduction of acyl chlorides?
What is the key outcome of the Rosenmund reduction of acyl chlorides?
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Which oxidizing agent can be used to convert toluene to benzaldehyde without reaching the benzoic acid stage?
Which oxidizing agent can be used to convert toluene to benzaldehyde without reaching the benzoic acid stage?
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What is the role of stannous chloride in the preparation of aldehydes from nitriles?
What is the role of stannous chloride in the preparation of aldehydes from nitriles?
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What is the product formed when toluene undergoes side chain chlorination followed by hydrolysis?
What is the product formed when toluene undergoes side chain chlorination followed by hydrolysis?
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Which reagent when treated with benzene and carbon monoxide, leads to the formation of benzaldehyde in the Gatterman-Koch reaction?
Which reagent when treated with benzene and carbon monoxide, leads to the formation of benzaldehyde in the Gatterman-Koch reaction?
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How are ketones formed from acyl chlorides using dialkylcadmium?
How are ketones formed from acyl chlorides using dialkylcadmium?
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What is the intermediate formed when nitriles are reduced by DIBAL-H?
What is the intermediate formed when nitriles are reduced by DIBAL-H?
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What type of reaction is the Stephen reaction primarily characterized by?
What type of reaction is the Stephen reaction primarily characterized by?
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Study Notes
Preparation of Aldehydes
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From acyl chlorides (acid chlorides):
- Acyl chlorides are hydrogenated over a palladium catalyst on barium sulfate. This process is called Rosenmund reduction.
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From nitriles and esters:
- Nitriles are reduced to imines using stannous chloride and hydrochloric acid. The imine is then hydrolyzed, producing the corresponding aldehyde.
- Alternatively, nitriles can be reduced directly to aldehydes using diisobutylaluminium hydride (DIBAL-H).
- Esters can be reduced to aldehydes using DIBAL-H.
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From aromatic hydrocarbons:
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Oxidation of methylbenzene:
- Strong oxidizing agents oxidize toluene and related compounds to benzoic acid. However, some reagents can stop the reaction at the aldehyde stage, converting the methyl group to a difficult-to-oxidize intermediate.
- Chromyl chloride (CrO₂Cl₂): Oxidizes the methyl group to a chromium complex that, on hydrolysis gives the corresponding benzaldehyde.
- Chromic oxide (CrO₃): Toluene or substituted toluene reacts with CrO₃ in acetic anhydride, forming benzylidene diacetate. Hydrolyzing benzylidene diacetate with aqueous acid produces benzaldehyde.
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Side chain chlorination followed by hydrolysis:
- Chlorinating the side chain of toluene creates benzal chloride. Further hydrolysis produces benzaldehyde. This method is commercially important.
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Preparation of Ketones
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From acyl chlorides:
- Treating acyl chlorides with dialkylcadmium, prepared from cadmium chloride and a Grignard reagent, forms ketones.
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Description
This quiz covers various methods for the preparation of aldehydes, including reactions from acyl chlorides, nitriles, esters, and aromatic hydrocarbons. Learn about key reagents and processes such as the Rosenmund reduction and oxidation reactions. Test your understanding of these organic chemistry concepts.
