Question

Correct statement(s) regarding following reaction sequence is: (A) P is 4-hydroxy pentanoic acid (B) In acidic condition P gives lactone (C) (R) on strong heating produces succinic anhydride (D) $Q$ can't decolourises ${\mathrm{Br}}_2/{\mathrm{H}}_2\mathrm{O}$ solution

Short answer

Based on the given reaction sequence, the correct statements are: (A) P is 4-hydroxy pentanoic acid (B) In acidic condition P gives lactone

Step-by-step solution

Identifying compound P

First, we need to identify the compound P. According to statement (A), P is 4-hydroxy pentanoic acid. The structure of 4-hydroxy pentanoic acid can be represented as: $$C{H}_{3}C{H}_{2}CH(OH)C{H}_{2}COOH$$

Formation of lactone from P

Next, we need to determine if P can form a lactone in acidic conditions (statement B). A lactone is an ester that forms by the intramolecular condensation of a hydroxyl group (-OH) and a carboxyl group (-COOH). In the case of 4-hydroxy pentanoic acid, the hydroxyl group is at the 4th carbon and the carboxylic acid group is at the 5th carbon. An intramolecular reaction can easily occur between these two functional groups to form a five-membered ring lactone. Therefore, statement B is correct.

Formation of succinic anhydride from R

Statement C states that on strong heating, compound R produces succinic anhydride. However, we do not have any information about compound R. As a result, we cannot determine if this statement is correct or false.

Decolorization of bromine water by Q

Finally, statement D claims that compound Q cannot decolorize bromine water (Br₂/H₂O). Decolorization of bromine water is a test for the presence of carbon-carbon double bonds (C=C) in a compound. In this case, we also do not have any information about compound Q, so we cannot determine if this statement is correct or false. Therefore, the correct statements regarding the following reaction sequence are: (A) P is 4-hydroxy pentanoic acid (B) In acidic condition P gives lactone

Key concepts

Lactone Formation

Lactone formation is a key organic reaction where a hydroxycarboxylic acid undergoes intramolecular esterification to form a cyclic ester, known as a lactone. This reaction is catalyzed by acid, which means it requires an acidic environment to proceed efficiently. A common example of hydroxycarboxylic acid is 4-hydroxy pentanoic acid, with the -OH group and the -COOH group within favorable proximity to form a lactone. For lactones with five or six-membered rings, this reaction is particularly favorable due to lower ring strain, leading to stable cyclic structures. This lactonization not only consolidates two functional groups into one but also significantly changes the chemical and physical properties of the compound.

4-Hydroxy Pentanoic Acid

4-hydroxy pentanoic acid is an organic compound characterized by the presence of both a hydroxyl (-OH) group and a carboxylic acid (-COOH) group. The hydroxyl group is located on the fourth carbon atom, and the carboxylic acid is at the terminal, or fifth, carbon atom. The closeness of these groups allows for the intramolecular formation of lactones under the right conditions. When discussing 4-hydroxy pentanoic acid, it's important to note that the hydroxyl position is key to the resulting lactone's size and properties. This compound is often used in exercises to illustrate the principles of functional group reactions and intramolecular esterification, which are foundational in organic synthesis.

Succinic Anhydride

Succinic anhydride is derived from succinic acid, a four-carbon dicarboxylic acid, through the loss of a water molecule, resulting in an anhydride. This compound has two anhydride functional groups, which make it very reactive, especially with alcohols and amines, producing succinate esters and amides, respectively. Additionally, succinic anhydride is used as a reagent in the laboratory to modify the chemical structure of other molecules, such as in acylation reactions where it introduces the succinyl functional group.

Decolorization of Bromine Water

Decolorization of bromine water is a qualitative test in organic chemistry used to detect unsaturation, such as carbon-carbon double bonds (C=C), in a molecule. Bromine water, which is a solution of bromine in water, has a distinct orange or brown color. When an unsaturated compound, containing double bonds, is added to bromine water, the double bonds react with the bromine causing the solution to lose its color. This reaction is also known as bromination. However, if the organic compound lacks such unsaturation, the bromine water remains colored. This test is simple and rapid, making it an effective tool for detecting alkene presence in a molecule.