Question

The correct statement regarding \(\mathrm{P}\) and \(\mathrm{Q}\) is CC(=O)CC(C)=O (A) Acidic strength order: \(\mathrm{P}>\mathrm{Q}>\mathrm{H}_{2} \mathrm{O}\) (C) It is a Perischiliv reaction (B) \(\mathrm{P}\) is white crystalline solid (D) P and Q can be distinguished by Fehling solution

Short answer

The correct statement regarding compounds P and Q is (A) Acidic strength order: \(\mathrm{P}>\mathrm{Q}>\mathrm{H}_{2} \mathrm{O}.\) P is an α-keto ester, which is more acidic than its reduced form Q (alcohol) and water.

Step-by-step solution

Identify the molecular structure in SMILES notation

The SMILES notation given is CC(=O)CC(C)=O. The structure can be drawn as follows: ``` CH3 - C(=O) - CH2 - C(=O) - CH3 ``` This is an α-keto ester molecule.

Identify compounds P and Q

Let's assign the α-keto ester molecule to compound P. Then, compound Q can be formed by reducing the carbonyl group (-C=O) of compound P to an alcoholic hydroxyl group (-C-OH).

Assess acidity of P, Q, and water

To rank the acidity of P, Q, and water, we need to compare their pKa values. Generally, water has a pKa value of around 15.7. Keto-esters generally have pKa values around 12, making them more acidic than water. Since P is an α-keto ester and Q is its reduced form (alcohol), P is more acidic than Q and water.

Determine the color and form of P

Compound P, being an α-keto ester, is usually colorless to slightly yellow crystalline solid at room temperature. Thus, option B, which states P is a white crystalline solid, cannot be ruled out as incorrect.

Explain the Perischiliv reaction

The Perischiliv reaction is not a recognized chemical reaction in the literature. It could be a typo or a misnomer, and without proper context, we cannot determine its relevance. Thus, option C cannot be confirmed as correct or incorrect.

Distinguishing P and Q using Fehling solution

Fehling's solution is used to distinguish reducing sugars and aldehydes from ketones. Since P has a ketone group and Q has an alcoholic hydroxyl group, Fehling's solution cannot differentiate between them. Therefore, option D is incorrect. Based on our analysis, the correct statement regarding P and Q is: (A) Acidic strength order: \(\mathrm{P}>\mathrm{Q}>\mathrm{H}_{2} \mathrm{O}.\)

Key concepts

α-keto ester

An α-keto ester is a chemical compound that features a ketone and an ester functional group at the alpha position. In other words, the carbon atom next to the ester functionality also houses a ketone group. These unique structural features give α-keto esters distinct properties.

Compounds like these are significant in organic chemistry because of their potential to participate in a variety of chemical reactions.
They are often utilized in synthesizing complex molecules due to their reactive nature. - **Structure**: The general structure is symbolized as RCOCOOR', where the R groups represent varying carbon-containing chains. - **Reactivity**: The presence of both ester and ketone functional groups increases the acidity of the compound compared to simple esters or ketones. - **Applications**: α-keto esters are important in the synthesis of amino acids and other biologically relevant molecules.

pKa values

The pKa value is a measure of the acidity of a compound. It denotes how easily a molecule can donate a proton (H+) in a chemical reaction.
Practically, the lower the pKa value, the stronger the acid. - **Relevance to α-keto esters**: These compounds typically have lower pKa values due to their structural attributes. The combination of ketone and ester groups enhances their acidity compared to water, which has a pKa of approximately 15.7.
Typically, α-keto esters have pKa values around 12, indicating their relatively higher acidity. - **Functional Group Influence**: The presence of electronegative atoms or groups near the acidic site increases acidity, lowering the pKa. This is why α-keto esters are more acidic than their alcohol counterparts. Understanding pKa values is crucial in predicting the behavior of molecules in chemical reactions, such as their ability to undergo substitution or elimination reactions.

Fehling's solution

Fehling’s solution is a chemical reagent used to differentiate between aldehydes and ketones, particularly in sugars. The test utilizes the presence of a cupric ion in Fehling's solution which is reduced to a red cuprous oxide precipitate in the presence of aldehydes. Understanding Fehling's test is essential for distinguishing specific types of carbonyl-containing compounds. - **Application in distinguishing compounds**: Fehling's solution is effective in identifying aldehydes due to their ability to be oxidized over ketones, which are resistant to oxidation under similar conditions.
This is why in our exercise, Fehling's solution cannot distinguish between the keto ester (compound P) and its reduced alcohol form (compound Q), as neither functions as a reducing agent like an aldehyde would. - **Limitations**: The solution cannot detect alcohols or ketones and will therefore not react with these groups, making its application limited to aldehyde identification. Fehling’s solution remains a valuable reagent in analytical chemistry for its reliability in the detection of reducing sugars and aldehydes.