MED-108 Organic Chemistry: Aldehydes & Ketones

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Questions and Answers

What is the primary difference between aldehydes and ketones in terms of their oxidation?

Ketones are more easily oxidized than aldehydes.

Aldehydes are more resistant to oxidation than ketones.

Ketones are more easily oxidized to aldehydes than to carboxylic acids.

Aldehydes are easily oxidized to carboxylic acids, while ketones are resistant to oxidation. (correct)

What is the purpose of Tollens' reagent in oxidation reactions?

To reduce the oxidation number of silver in the reaction.

To catalyze the oxidation of aldehydes to carboxylic acids.

To create a highly acidic environment for the reaction.

To test for the presence of aldehydes in a molecule. (correct)

Which of the following oxidizing agents is used in alkaline conditions?

Na2Cr2O7 (K2Cr2O7) in acid.

KMnO4 in hot HNO3.

CrO3 in strongly acidic conditions.

Ag2O in aqueous ammonia solution. (correct)

What is the oxidation number of silver in Ag2O?

+1 Signup and view all the answers

What is the result of the reduction of silver in the Tollens' test?

The formation of silver atoms. Signup and view all the answers

What is the result of the reduction reaction when Tollens' reagent is added?

Elemental silver deposits on the test tube walls Signup and view all the answers

What is the nature of the carbonyl group?

Polarized due to the difference in electronegativities between C and O Signup and view all the answers

What is the product of the nucleophilic addition of water to an aldehyde or ketone?

A 1,1-diol (geminal diol) Signup and view all the answers

What is the purpose of adding an acid to the O- ion?

To protonate the O- ion, forming an –OH group Signup and view all the answers

What is the result of the reduction of the –CN group in a cyanohydrin?

Formation of a primary amine (-CH2NH2) Signup and view all the answers

What is the purpose of using a milder oxidizing agent in the partial oxidation of primary alcohols to prepare aldehydes?

To prevent over-oxidation to a carboxylic acid Signup and view all the answers

What type of alkyne is required for the hydroboration-oxidation reaction to prepare an aldehyde?

Terminal alkyne Signup and view all the answers

Which of the following reactions is used to prepare ketones from secondary alcohols?

Oxidation of secondary alcohols Signup and view all the answers

What is the oxidizing agent used in the partial oxidation of primary alcohols to prepare aldehydes?

PCC (pyridinium chlorochromate) Signup and view all the answers

What is the outcome of using internal alkynes in the hydroboration-oxidation reaction?

Formation of a mixture of ketones Signup and view all the answers

What is the result of oxidation of aldehydes under acidic or alkaline conditions?

Formation of a carboxylic acid Signup and view all the answers

What is the characteristic of ketones regarding oxidation?

They are resistant to oxidation Signup and view all the answers

What is the reagent used for oxidizing aldehydes under alkaline conditions?

Tollens' reagent Signup and view all the answers

What is the product formed when water is added to a carbonyl group?

A geminal diol Signup and view all the answers

What is the purpose of the Wolff-Kishner reaction?

To reduce a carbonyl group to a methylene group Signup and view all the answers

Study Notes

Grignard Reagents

Grignard reagents are important in organic chemistry
Hydrazine (N2H4) is a nucleophile that converts a carbonyl group (C=O) to -CH2 through reduction
Wolff-Kishner reaction is a method of converting a carbonyl group to -CH2

Preparation of Aldehydes and Ketones

Aldehydes can be prepared by:
- Partial oxidation of primary alcohols
- Ozonolysis of appropriate alkenes
- Partial reduction of an ester
- Hydroboration-oxidation of terminal alkynes
Ketones can be prepared by:
- Oxidation of secondary alcohols
- Ozonolysis of appropriate alkenes
- Hydroboration-oxidation of internal alkynes
- Mercury(II)-catalyzed hydration of terminal and internal alkynes

Characteristics of Aldehydes and Ketones

Aldehydes can be easily oxidized to carboxylic acids using various oxidizing agents
Ketones are resistant to oxidation, but can react under harsh conditions to form carboxylic acids
Aldehydes and ketones have a carbonyl group (C=O) which is polarized due to the difference in electronegativities between C and O
This polarity makes the C atom susceptible to attack by electron-rich nucleophiles

Nucleophilic Addition

Nucleophilic addition reactions involve the attack of a nucleophile on the partially positive C atom of the carbonyl group
Nucleophiles can be fully negative ions (e.g. OH-, CN-, H-) or neutral but polar molecules (e.g. H2O, R-OH)
Examples of nucleophilic addition reactions include:
- Hydration (addition of water) to form a 1,1-diol (geminal diol)
- Cyanohydrin formation (addition of HCN)

Transformations of Cyanohydrins

Cyanohydrins can be transformed into useful compounds through:
- Reduction of the -CN group to -CH2NH2
- Hydrolysis of the -CN group to -COOH

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Description

Test your knowledge of aldehydes and ketones in organic chemistry. Learn methods of preparation, reagents, and products of various reactions. Review reactions and introduce new ones in this comprehensive quiz.