MEDCHEM 12 Notes

These flashcards cover key concepts related to aldehydes and ketones, their reactions, properties, preparation methods, and applications in medicinal and pharmaceutical chemistry.

What are aldol condensation reactions?

Reactions that involve the nucleophilic addition of aldehydes or ketones leading to the formation of aldols.

What structures are involved in collagen?

Collagen is made up of tropocollagen, which contains three helices of protein chains linked by hydrogen bonds.

How is the oxidation level of carbon calculated in carbonyl compounds?

By counting the number of bonds between the carbon and atoms other than hydrogen and carbon.

What are the two types of carbonyl compounds discussed?

Aldehydes and ketones.

Why are hydrogens on a-carbon considered slightly acidic?

Because deprotonation produces an enolate, which is stabilized by resonance.

What is the role of a strong base in aldol reactions?

A strong base, in catalytic quantities, is required for the nucleophilic addition in the aldol reaction.

What is the product of an aldol reaction?

An aldol is produced, which can further dehydrate to form an enal.

What is formed during the dehydration of aldol products?

An enal is formed after the removal of water.

What distinguishes the oxidation of aldehydes and ketones?

Aldehydes can be oxidized to carboxylic acids, whereas ketones cannot be oxidized by Tollens’ or Fehling’s tests.

What is Tollens' reagent used for?

To distinguish aldehydes from ketones through the silver mirror test.

What happens in a Tollens' reaction when an aldehyde is present?

The aldehyde is oxidized to a carboxylic acid, and silver is reduced to form a silver mirror.

What occurs in a Fehling’s solution test?

Aldehydes are oxidized to carboxylic acids, resulting in a brick red precipitate, while ketones remain unchanged.

How can aldehydes be prepared from alcohols?

By oxidation of primary alcohols using oxidizing agents like pyridinium chlorochromate (PCC).

What is the oxidation level of a carbon affected by?

The number of bonds the carbon forms with atoms other than hydrogen and carbon.

What is an enolate?

A resonance-stabilized intermediate formed when a carbon on a carbonyl compound is deprotonated.

What is the significance of resonance in acidity regarding a-carbon?

It stabilizes the anion formed after deprotonation, making the alpha hydrogen slightly acidic.

What type of alcohols are formed from the reduction of aldehydes?

Primary alcohols.

What type of alcohols are formed from the reduction of ketones?

Secondary alcohols.

What are the intramolecular cross-links in collagen linked by?

These links are formed by aldol condensations, stabilized by enzymatic control.

What characterizes the aldol condensation reaction?

It involves nucleophilic addition followed by dehydration.

Which reagent is specifically used for oxidizing aldehydes to carboxylic acids?

Tollens' reagent.

What does the enzymatic action of Lysyl Oxidase do in collagen?

It oxidizes lysine side chains to form aldehydes that facilitate cross-linking.

What is required for an aldol reaction to occur?

At least one hydrogen on a-carbon and the presence of a strong base.

Why is pyridinium chlorochromate (PCC) used in oxidizing alcohols?

It selectively oxidizes primary alcohols to aldehydes without over-oxidizing to carboxylic acids.

What is the result of the aldol reaction involving a-carbon with two hydrogens?

It can carry out nucleophilic addition to form an aldol.

What is produced from the dehydration of an aldol?

An enal.

What happens to the structure of collagen during aging?

The amount of cross-linking increases, affecting its mechanical strength.

What distinguishes aldehydes from ketones in terms of reactivity?

Aldehydes are oxidizable to carboxylic acids, while ketones are not.

What type of forces stabilize tropocollagen in collagen?

Hydrogen bonds between helices.

What conditions facilitate the formation of enolates in aldol reactions?

Strong basic conditions and presence of hydrogen on a-carbon.

What makes aldehyde and ketone reactions with Tollens’ reagent particularly useful?

They provide methods to differentiate between these functional groups based on oxidization.

What is the expected product when a primary alcohol is oxidized?

An aldehyde or carboxylic acid depending on the oxidizing agent used.

What type of chemical change occurs in oxidation of aldehydes?

An increase in the oxidation state as electrons are removed.

What is a common biological reducing agent used in the reduction of aldehydes and ketones?

NADH.

How does the number of alpha hydrogen affect aldol reactions?

Higher counts allow for more complex aldol condensation reactions.

What are characteristics of aldol reactions that involve dehydration?

They require either acid catalysts or high temperatures to promote the loss of water.

What type of reactions do Klein and Oxidase catalyzed transformations represent?

They represent enzymatic reactions leading to cross-link formation.

What determines the class of alcohol produced from a ketone reduction?

Whether the carbonyl was treated with a hydride ion or another reducing agent.

What is displayed by the presence of a silver mirror in a test tube?

The presence of aldehydes in a solution tested with Tollens’ reagent.

What defines the mechanistic path of aldol reactions?

The nucleophilic addition of an enolate to a carbonyl compound followed by dehydration to form an enal.

What physiological role do collagen's cross-links play?

They provide structural integrity and mechanical strength to tissues.

In terms of oxidation, how can you classify the conversion of primary alcohol to a carboxylic acid?

It is classified as oxidation due to the increase in the oxidation level.

How can you tell if a reaction is a reduction?

By observing a decrease in the oxidation state of the reactants.