Question

Predict the product formed by the reaction of diethy 1 malonate with sodium ethoxide and ethyl nitrite in ethanol solution. Write a mechanism for the formation of this product.

Short answer

The product formed by the reaction of diethyl malonate with sodium ethoxide and ethyl nitrite in ethanol solution is an α-nitro carboxylic acid: \((CH(CO_2Et)_2N=C(COOH))\). The mechanism involves deprotonation of diethyl malonate, nucleophilic attack, rearrangement, and hydrolysis.

Step-by-step solution

Write the structures of the reactants

Diethyl malonate: \(CH_2(CO_2Et)_2\) Sodium ethoxide: \(NaOCH_2CH_3\) Ethyl nitrite: \(C_2H_5ONO\)

Determine nucleophilic and electrophilic centers in the reactants

In diethyl malonate, thealpha carbon (the carbon between the two carbonyl groups) is a nucleophilic center since it contains acidic protons that can be deprotonated by a strong base. Sodium ethoxide is a strong base that can act as a nucleophile. The oxygen of the ethoxide ion is the nucleophilic center. Ethyl nitrite has an electrophilic nitrite group, and the nitrogen has a positive charge, making it an electrophilic center.

Propose a mechanism for the reaction

1. Deprotonation of diethyl malonate: Sodium ethoxide acts as a base and deprotonates the alpha carbon of diethyl malonate, forming an enolate ion and sodium ion. \(CH_2(CO_2Et)_2 + NaOCH_2CH_3 -> NaCH(CO_2Et)_2^- + CH_3CH_2OH\) 2. Nucleophilic attack: The enolate ion acts as a nucleophile and attacks the electrophilic nitrogen center in ethyl nitrite, producing a new C-N bond. \(NaCH(CO_2Et)_2^- + C_2H_5ONO -> CH(CO_2Et)_2N(OC_2H_5) + NaO^-\) 3. Rearrangement: The O-N bond in the intermediate is cleaved, and the O^- is eliminated. A new C=O bond is formed, and the ester group becomes an aldehyde. \(CH(CO_2Et)_2N(OC_2H_5) -> CH(CO_2Et)_2N=C(CHO) + C_2H_5O^-\) 4. Hydrolysis: The intermediate is hydrolyzed in the ethanol solution, and the aldehyde is converted into a carboxylic acid. \( CH(CO_2Et)_2N=C(CHO) + H_2O -> CH(CO_2Et)_2N=C(COOH)\)

Specify the product formed as a result of the reaction

The product formed by the reaction of diethyl malonate with sodium ethoxide and ethyl nitrite in ethanol solution is an α-nitro carboxylic acid: \((CH(CO_2Et)_2N=C(COOH))\)

Key concepts

Diethyl Malonate

Diethyl malonate is a versatile compound in organic chemistry known for its ability to undergo numerous reactions. It has the chemical structure \( CH_2(CO_2Et)_2 \), where two ethyl ester groups are bonded to the carbon atom. This carbon atom is connected to two carbonyl groups, forming an alpha position that is susceptible to deprotonation.

This compound is significant in various synthesis processes such as the malonic ester synthesis. It is particularly useful for synthesizing substituted acids through reactions involving enolate ion formation, where the carbon at the alpha position is made reactive for further chemical transformations.

• Used widely as a building block in organic synthesis
• Contains two reactive ethyl ester groups
• Alpha carbon is essential for further reaction steps

Nucleophilic Attack

Nucleophilic attack is a fundamental concept in organic chemistry where a nucleophile donates an electron pair to electrophilic centers, forming a chemical bond. In the context of diethyl malonate reactions, the nucleophilic attack involves the enolate ion.

The enolate, formed from diethyl malonate after deprotonation, acts as a nucleophile. In our reaction, this nucleophile interacts with the electrophilic nitrogen in ethyl nitrite, leading to a new chemical bond. This crucial step facilitates the formation of an \( \alpha \)-nitro carboxylic acid, showcasing the importance of precise molecular interactions.

• Involves electron-rich species (nucleophile) attacking electron-poor centers (electrophile)
• Forms new bonds that are crucial for constructing complex molecules
• Key step in many organic synthesis reactions

Electrophilic Centers

An electrophilic center is a site within a molecule that can accept electrons from a nucleophile. In this reaction, multiple electrophilic centers are crucial, such as the nitrogen in ethyl nitrite.

This nitrogen atom, bearing a positive charge, is especially reactive, making it an ideal target during the nucleophilic attack. By interacting with nucleophiles like the enolate ion, it facilitates the rearrangement and transformation of the reactants into the desired product, demonstrating the role of electrophilic centers in driving the reaction mechanism.

• Positively charged or electron-deficient sites
• Essential for bonding with nucleophiles
• Crucial for reaction progression and product formation

Enolate Ion Formation

Enolate ion formation is a critical step in many organic reactions. When diethyl malonate reacts with sodium ethoxide, the acidic hydrogen on the alpha carbon is removed, resulting in an enolate ion. This ion is extremely reactive due to its negative charge and critical for subsequent steps.

The enolate ion, rich in electrons, serves as a potent nucleophile. It initiates the nucleophilic attack on electrophilic centers, as seen in interactions with ethyl nitrite in this specific reaction. This initial ion generation is pivotal, marking the commencement of complex molecular transformations.

• Generated by the action of a strong base, such as sodium ethoxide
• Serves as a key nucleophile in organic reactions
• Enables the construction of more intricate molecules through further steps