Question

The enol form of acetone, after treatment with \(\mathrm{D}_{2} \mathrm{O}\), gives

Short answer

The enol form of acetone, after treatment with \(\mathrm{D}_{2} \mathrm{O}\), gives \(\mathrm{D}\cdot\mathrm{C}(\mathrm{OD})\cdot\mathrm{CD}_2\).

Step-by-step solution

Understand the Enol Form

The enol form of acetone, also referred to as an enol tautomer, is created by deprotonating the methyl group and redistributing a hydrogen atom, resulting in the formation of a hydroxyl group. The structure is typically represented as \( \mathrm{H}\cdot\mathrm{C}(\mathrm{OH})\cdot\mathrm{CH}_2\).

Reaction with \(\mathrm{D}_{2}\mathrm{O}\)

When the enol tautomer of acetone reacts with \(\mathrm{D}_{2}\mathrm{O}\), the enol hydroxyl group can participate in an exchange reaction, where the hydrogen in the hydroxyl group is replaced by a deuterium atom from \(\mathrm{D}_{2}\mathrm{O}\).

Examine Proton Exchange

In the exchange process, hydrogen atoms adjacent to carbon atoms can also undergo exchange with deuterium from \(\mathrm{D}_{2}\mathrm{O}\). This primarily occurs at the \(\alpha\)-carbon (carbon directly connected to the carbonyl group). Thus, all protons at the \(\alpha\)-position can be replaced by deuterium atoms.

Check for Non-reactive Portions

Note that the carbonyl group itself (c\(C=O\)) does not participate in the exchange of its oxygen or carbon atoms because it is not directly involved in the tautomeric or exchange processes with \(\mathrm{D}_{2}\mathrm{O}\). Only the enol form and \(\alpha\)-protons participate actively.

Write the Final Structure

After all the exchange has occurred in the enol form, the final structure of the exchanged molecule will be \(\mathrm{D}\cdot\mathrm{C}(\mathrm{OD})\cdot\mathrm{CD}_2\). Here, all hydrogens in the enol form have been replaced by deuterium due to treatment with \(\mathrm{D}_{2}\mathrm{O}\).

Key concepts

Proton Exchange Reactions

Proton exchange reactions involve the replacement of protons (H⁺ ions) within a molecule by other isotopes, such as deuterium (D). In the case of enol tautomerism of acetone, when acetone transforms into its enol form, specific hydrogens in the molecule become more reactive and are capable of participating in exchange reactions. The enol form has a hydroxyl group (OH) that can readily exchange its hydrogen atom with deuterium from a compound like deuterium oxide (32;O). Additionally, when water is used in these reactions, these exchange processes are typically facilitated by the catalyst's presence. Proton exchange reactions are crucial in studying molecular structures and reaction mechanisms, offering insights into reaction pathways and isotope effects.

They also play a vital role in metabolic studies, understanding how drugs interact with the body, and are used in labeling molecules for various analytical purposes.

Deuteration

Deuteration is the process of replacing hydrogen atoms in a molecule with deuterium, an isotope of hydrogen. This chemical technique is essential for exploring reaction mechanisms and dynamic systems within chemistry.

Compared to hydrogen, deuterium has a greater atomic mass, which affects the physical properties of molecules, such as their vibrational modes. These subtle changes can lead to major differences in chemical behavior and isotopic distribution within a molecule.

In the context of enol tautomerism of acetone, deuteration occurs when the enol form reacts with deuterium oxide (32;O). This reaction results in the replacement of hydrogen atoms in the hydroxyl group and adjacent carbons with deuterium. Deuteration is not only a useful analytical tool but also has practical applications in areas like pharmaceuticals, where deuterated drugs may show improved pharmacokinetic properties.

Alpha Carbon Substitution

Alpha carbon substitution refers to reactions occurring at the 3; position of a carbonyl compound, like acetone, which is the carbon directly attached to the carbonyl group.3; carbon atoms are particularly reactive and form crucial sites for chemical modifications.

In the enol form of acetone, 3; carbons can participate in exchange reactions with deuterium from 32;O.3; protons, which are the hydrogens attached to these 3; carbons, are highly exchangeable and can be substituted, or swapped, for deuterium atoms. This substitution occurs because the 3; carbon's slightly acidic protons are more readily removable in an enolic environment.

Substitution at the 3; carbon is a key focus in many reactions, enhancing our understanding of both reaction mechanisms and the reactivity profiles of molecules. This type of substitution is often leveraged in designing novel compounds and investigating their metabolic fates.

Acetone

Acetone is a simple, yet multifunctional compound known for its role as a solvent and as a central component in various chemical reactions. Its chemical structure is composed of three carbon atoms, a central carbonyl group (C=O), and two methyl groups 32;3;). Acetone is frequently used in laboratories due to its ability to dissolve many organic compounds.

In the context of enol tautomerism, acetone can form an enol tautomer through proton exchange reactions. Acetone's enol form is structurally different from its keto form, showing how dynamic and versatile this compound can be.

• It serves as a model compound for studying keto-enol tautomerization.
• In biological systems, acetone is a small but important part of various metabolic pathways.

Additionally, acetone's reactions with isotopes like deuterium provide significant insights into chemical kinetics and reaction pathways, making it an essential chemical for study in both academic and practical settings.