Question

The product obtained on reaction of malonic acid with \(\mathrm{P}_{2} \mathrm{O}_{5} / \Delta\) is

Short answer

The product obtained on reaction of malonic acid with \(P_2O_5/\Delta\) is propanedioic anhydride, with the molecular formula C3H2O3.

Step-by-step solution

Write the structural formula of malonic acid

Malonic acid, also known as propanedioic acid, has the molecular formula C3H4O4. Its structural formula can be represented as \(-\)OOC\-CH2\-COOH.

Understand the role of P2O5 in the reaction

Phosphorus pentoxide (P2O5) is a powerful dehydrating agent. In this reaction, P2O5 removes a water molecule (\(H_2O\)) from malonic acid.

Predict the product formed

To predict the product formed from the reaction, we need to determine which atoms will be involved in the elimination of the water molecule. In malonic acid, there are two carboxylic acid groups. One water molecule can be formed by the removal of one hydroxyl (\(-OH\)) group from one carboxylic acid group and a hydrogen atom from another carboxylic acid group. So, the reaction will proceed as follows: \[-OOC-CH_2-COOH + P_2O_5 / \Delta \rightarrow -OOC-CH_2-CO + H_2O\] In this case, the product formed is an anhydride, also known as propanedioic anhydride, with the molecular formula C3H2O3.

Key concepts

Understanding Malonic Acid

Malonic acid, also known scientifically as propanedioic acid, is a simple dicarboxylic acid with the chemical formula \(\text{C}_3\text{H}_4\text{O}_4\). It is composed of three carbon atoms, four hydrogen atoms, and four oxygen atoms.
Malonic acid serves as a key ingredient in many chemical reactions in organic chemistry. It is primarily recognized for its tendency to participate in various condensation reactions.
When drawing its structure, you will notice it features two carboxylic acid groups (-COOH) flanking a methylene group (-CH2-). This positioning makes it particularly reactive.

• The presence of two carboxyl groups makes it an excellent starting material for synthesizing other compounds.
• Because of its reactivity, malonic acid is used in the creation of compounds that might serve medicinal functions, such as in pharmaceuticals.

Understanding its structure and reactive properties helps in comprehending its behavior in chemical reactions, such as when it interacts with phosphorus pentoxide.

Role of Phosphorus Pentoxide

Phosphorus pentoxide (\(\text{P}_2\text{O}_5\)) is a highly effective dehydrating agent often utilized in organic chemistry. Its primary function is to remove water molecules from other compounds, making it a critical reagent in reactions where dehydration is required.
Let's delve into how \(\text{P}_2\text{O}_5\) operates in reaction settings, especially with acids like malonic acid.

• It operates by forming water with the available hydrogen and hydroxyl groups from the compound.
• It encourages the elimination of water and assists in converting acids to anhydrides or other dehydrated derivatives.

In reactions with malonic acid, phosphorus pentoxide facilitates the removal of a water molecule, leading to the formation of an anhydride. This role highlights its importance as a catalyst in enhancing reaction efficiency and yield.

Anhydride Formation Explained

Anhydride formation is a key process in organic chemistry reactions, especially involving carboxylic acids like malonic acid. An anhydride is essentially a compound derived from another compound (commonly an acid) by removing a water molecule.
The reaction involving malonic acid and phosphorus pentoxide beautifully illustrates this concept. Through the use of \(\text{P}_2\text{O}_5\), a molecule of water is abstracted from malonic acid, following the removal of an -OH group from one carboxylic acid moiety and a hydrogen from another.
This results in the generation of an anhydride with the formula \(\text{C}_3\text{H}_2\text{O}_3\), known as propanedioic anhydride.

• Anhydrides have unique properties and reactivities different from their parent acids, often used in industrial and pharmaceutical chemistry.
• Understanding the formation of anhydrides helps in designing pathways for complex chemical synthesis.

This reaction pathway not only underscores the fundamentals of anhydride formation but also exemplifies the interplay of structural rearrangement and dehydration in organic reactions.