Problem 120 - Arihant Objective Approach to Organic Chemistry for IIT JEE and NEET all Medical Entrances Part 4

Question

DDT is obtained when chlorobenzene reacts with: [HR (PMT) \(1996 \mid\) (a) acetaldehyde (b) acetone (c) chloral (d) phenol

Step-by-Step Solution

Answer

Option (c) chloral.

Step 1: Understanding the Reaction

DDT (Dichlorodiphenyltrichloroethane) is a chemical compound obtained from a reaction. We need to understand which of the given options reacts with chlorobenzene to produce DDT.

Step 2: Identifying the Reactants of DDT

DDT is synthesized by the reaction of chloral (CCl₃CHO) with chlorobenzene (C₆H₅Cl) in the presence of a catalyst, often concentrated sulfuric acid (H₂SO₄). Therefore, out of the given options, chloral is the correct reactant that combines with chlorobenzene to form DDT.

Step 3: Verifying the Correct Option

Review the options given: (a) acetaldehyde, (b) acetone, (c) chloral, and (d) phenol. Recognizing that DDT is formed by combining chlorobenzene with chloral confirms option (c) as the correct answer.

Key Concepts

DDT Synthesis

DDT, short for Dichlorodiphenyltrichloroethane, is a well-known synthetic compound.Synthesizing DDT involves a chemical reaction between chlorobenzene and chloral. This reaction typically occurs in the presence of a catalyst, often concentrated sulfuric acid.- **Chlorobenzene** (\(C_6H_5Cl\)) is a derivative of benzene where one hydrogen atom is replaced by a chlorine atom. It serves as the aromatic coupling partner in this reaction.- **Chloral** (\(CCl_3CHO\)) is a chlorinated aldehyde that reacts with chlorobenzene to form DDT by a condensation reaction.The interaction of these chemicals leads to the formation of DDT, which was historically used as an insecticide. Understanding the synthesis of DDT provides insight into how specific reactants can form complex compounds with significant applications.

Chloral

Chloral, or trichloroacetaldehyde, is a key compound in organic synthesis.This aldehyde has the chemical formula \(CCl_3CHO\). It consists of a carbonyl group linked to a trichloromethyl group. Such a structure gives chloral its distinctive reactive properties, especially in the synthesis of DDT.When chloral reacts with chlorobenzene, it partakes in a condensation reaction. A catalyst such as sulfuric acid is commonly used to facilitate this reaction. This leads to the formation of the much larger molecule, DDT.Chloral serves as an excellent example within organic chemistry for understanding how aldehydes can form bonds with aromatic compounds. Understanding chloral's reactivity is key for anyone studying organic synthesis, especially in historical contexts where compounds like DDT were widely produced and used.

Chemical Reactions in Organic Chemistry

Organic chemistry is filled with fascinating chemical reactions that transform simple molecules into complex compounds. The reaction of chlorobenzene with chloral to form DDT is just one example of these organic transformations. - **Condensation Reaction**: This type of reaction involves the joining of two molecules with the loss of a small molecule, such as water or hydrochloric acid. In the synthesis of DDT, chlorobenzene and chloral undergo a condensation reaction. - **Catalysts**: These are substances that increase the rate of a chemical reaction without being consumed. In organic reactions, catalysts like sulfuric acid are crucial. They help in faster and more efficient reactions, enabling the formation of products like DDT. Understanding these concepts helps unravel how organic chemists design reactions to obtain desired compounds. These principles underpin much of organic synthesis and are crucial for anyone studying chemistry at an advanced level.