Medicinal & Pharmaceutical Chemistry - Aldehydes and Ketones

A comprehensive set of flashcards summarizing key concepts and reactions involving aldehydes and ketones in medicinal and pharmaceutical chemistry.

What is the general structure of aldehydes?

An aldehyde has the structure R-CHO, where R can be hydrogen or a carbon-containing group.

What is the general structure of ketones?

A ketone has the structure R1-CO-R2, where R1 and R2 are carbon-containing groups.

What is the primary functional group of carbonyl compounds?

The carbonyl group (C=O) is the primary functional group.

What determines the polarity of carbonyl compounds?

The difference in electronegativity between carbon and oxygen in the C=O bond.

Which is generally more reactive towards nucleophiles, aldehydes or ketones?

Aldehydes are generally more reactive than ketones.

What is a nucleophile?

A nucleophile is a species that donates an electron pair to form a chemical bond.

How does steric hindrance affect the reactivity of ketones compared to aldehydes?

Aldehydes are generally more reactive than ketones due to less steric hindrance. The larger alkyl groups around the carbonyl carbon create more steric bulk, hindering nucleophilic attack and the electron-donating effects of alkyl groups that stabilize the carbonyl.

What happens to the bond angles in the reaction involving the carbonyl group?

The bond angles reduce due to steric hindrance as substituents move closer together ( tetrahedral arrangement 109 ) around the carbonyl carbon.

What type of reaction do aldehydes and ketones undergo with alcohols?

Aldehydes and ketones undergo nucleophilic addition reactions with alcohols.

What is a hemiacetal?

A hemiacetal is a compound formed from the reaction of an aldehyde or ketone with an alcohol ratio 1:1 , containing one ether and one alcohol functional group.

What differentiates an acetal from a hemiacetal?

An acetal has two ether functional groups, while a hemiacetal has one ether and one alcohol functional group.

Which group is more electrophilic in carbonyl compounds, aldehydes or ketones?

Aldehydes are more electrophilic than ketones.

What is the role of acid in the nucleophilic addition of alcohols to carbonyl compounds?

Acid catalysis increases the electrophilicity of the carbonyl group.

Define oxime.

An oxime is a compound formed from the reaction of a carbonyl compound with hydroxylamine.

What is a hydrazone?

A hydrazone is a compound formed from the reaction of a carbonyl compound with a hydrazine.

Why is nitrogen considered a better nucleophile than oxygen in carbonyl reactions?

Nitrogen has a lone pair of electrons and is less electronegative, making it a better nucleophile.

What stabilizes the cyclic hemiacetals formed by sugars like glucose?

The most stable cyclic hemiacetal of glucose is a six-membered ring.

What is the significance of the C=O bond in aldehydes and ketones?

The C=O bond is polar, making the carbonyl carbon electrophilic and reactive towards nucleophiles.

Describe the general mechanism for the formation of an imine from a carbonyl compound and an amine.

The carbonyl compound reacts with the amine to form an imine through nucleophilic addition and subsequent elimination of water.

How does the presence of bulkier groups affect ketone reactivity?

Bulkier groups in ketones lead to increased steric hindrance, decreasing reactivity.

In the formation of hemiacetals, what occurs first?

The carbonyl group is protonated to become a stronger electrophile.

What is the effect of increasing nucleophilicity of alcohols on their reaction with carbonyl compounds?

Increased nucleophilicity of alcohols can enhance the rate of their reaction with carbonyl compounds.

What is the condition for the conversion of a hemiacetal to an acetal?

The presence of excess alcohol facilitates the conversion of hemiacetals to acetals.

In the context of polar carbonyl compounds, what is the effect of electronegativity?

Oxygen being more electronegative than carbon contributes to the polarity of the carbonyl group.

What type of reaction is observed when amines react with carbonyl compounds?

A nucleophilic addition reaction that may lead to the formation of imines, oximes, or hydrazones.

What type of bond angles are present around carbonyl carbon?

The bond angles around the carbonyl carbon are approximately 120 degrees, indicating trigonal planar geometry.

How does an electron-donating group affect the reactivity of aldehydes and ketones?

Electron-donating groups generally decrease the electrophilicity of the carbonyl carbon.

What can trigger the nucleophilic addition reaction of oxygen nucleophiles?

Protonation of the carbonyl group enhances electron deficiency, making it more susceptible to nucleophilic attack.

What are the typical products of oxidizing a primary amine with a carbonyl compound?

The products include imines or oximes, depending on the substituent on the amine.

Can reactions of aldehydes and ketones with nitrogen nucleophiles involve catalysts?

Yes, catalysis can promote the reaction, although it's not essential for nitrogen nucleophiles.

Why are reactions with nitrogen nucleophiles often faster?

Nitrogen nucleophiles have higher nucleophilicity compared to oxygen nucleophiles.

What impact do electron-withdrawing groups have on the carbonyl carbon?

They increase the electrophilicity of the carbonyl carbon, facilitating nucleophilic attack.

In terms of product formation, how does the stoichiometry of alcohol in the reaction influence the outcome?

1:1 ratio yields hemiacetals, and 1:2 ratio yields acetals when reacted with aldehydes or ketones.

What do we mean when referring to the 'reactivity of carbonyl compounds'?

It describes how readily a carbonyl compound reacts with nucleophiles based on electrophilicity and steric factors.

How is hydroxylamine used in organic synthesis?

Hydroxylamine reacts with carbonyl compounds to form oximes, which can be useful for identifying aldehydes and ketones.

Why might one consider the steric effects surrounding ketones as a reactivity factor?

Steric effects can shield the electrophilic carbon, reducing the likelihood of nucleophilic attack.

What is the role of water in the conversion of hemiacetals to acetals?

Water is eliminated during this condensation reaction, completing the formation of acetals.

How can reaction rates be increased in nucleophilic addition reactions?

By manipulating the electrophilicity or the nucleophilicity of the reactants, such as using acids or bases.

What is the functionality of the carbonyl group in terms of its reactivity?

The carbonyl group acts as an electrophile, attracting nucleophiles for addition reactions.

What type of reaction mechanism is ideal for aldol reactions involving carbonyl compounds?

An addition-elimination mechanism is often used in aldol reactions.

Discuss the nature of the bond formed in imine synthesis from aldehydes or ketones.

The bond formed is a C=N double bond during the formation of imines.

How does the reactivity of aldehydes compare with cyclopropyl ketones?

Aldehydes are generally more reactive towards nucleophiles compared to cyclopropyl ketones due to less steric hindrance.

How does one identify the product formed from the reaction of a carbonyl compound with 2,4-dinitrophenylhydrazine?

The product is a hydrazone, which can be used as a diagnostic tool to identify carbonyl compounds.

What is a two-step mechanism in the context of aldehyde reactions?

It typically involves nucleophilic addition followed by elimination of a leaving group.

Summarize the overall conversion of an amino alcohol in terms of imine formation.

An amino alcohol can convert through nucleophilic addition to form an imine, oxime, or hydrazone.

What is a common feature shared between hemiacetals, acetals, and related compounds?

All can undergo reversible reactions with carbonyl compounds.

How can reactions with nitrogen nucleophiles be differentiated from those with oxygen nucleophiles?

Nitrogen nucleophiles typically react faster, leading to different types of product formations.

How does the carbonyl group contribute to the formation of biologically relevant compounds?

The carbonyl group's reactivity allows for the formation of sugars, amino acids, and other biomolecules.

Explain the term 'nucleophilic substitution'.

It's a reaction in which a nucleophile replaces a leaving group in a molecule.

What experimental evidence can indicate the presence of aldehydes or ketones?

The formation of colored precipitates with 2,4-dinitrophenylhydrazine can indicate their presence.

What general principle governs the mechanism of nucleophilic addition reactions?

The mechanism typically follows an essential sequence of activation, addition, and elimination.

In an added context, how do aldehydes exhibit different properties compared to ketones?

Aldehydes often possess stronger odors and can be more reactive than ketones.

Lastly, what can summarizing notes about aldehydes and ketones help students with?

It can reinforce learning and recalling vital reaction mechanisms and product formations for exams.