Problem 43 - A Complete Resource Book in Chemistry for JEE Main

Question

\(\mathrm{CH}_{3} \mathrm{CHCl}_{2}\), on hydrolysis will give (a) \(\mathrm{CH}_{3} \mathrm{CHO}\) (b) \(\mathrm{CH}_{3} \mathrm{COOH}\) (c) \(\mathrm{CHCl}_{3}\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\)

Step-by-Step Solution

Answer

The hydrolysis of \( \mathrm{CH}_{3} \mathrm{CHCl}_{2} \) yields \( \mathrm{CH}_{3} \mathrm{CHO} \).

Step 1: Understand the Given Compound

The compound given is \( \mathrm{CH}_{3} \mathrm{CHCl}_{2} \), which is also known as 1,1-dichloroethane. This compound consists of an ethane molecule with two chlorine atoms attached to one of the carbon atoms.

Step 2: Conceptualize Hydrolysis

Hydrolysis involves a reaction with water. In the context of organohalides like 1,1-dichloroethane, hydrolysis can lead to the replacement of chlorine atoms with hydroxyl groups (\( -OH \)). This typically results in the formation of an alcohol or other oxygen-containing compound.

Step 3: Predict the Hydrolysis Product

During the hydrolysis of \( \mathrm{CH}_{3} \mathrm{CHCl}_{2} \), both chlorine atoms are replaced with \( -OH \) groups. This substitution results in the formation of a dihydroxy compound, which can then rearrange or lose water (\( \mathrm{H}_{2} \mathrm{O} \)) to form a carbonyl compound.

Step 4: Identify the Main Hydrolysis Product

The compound formed immediately after the hydrolysis is ethane-1,1-diol, which is unstable. Upon losing a molecule of \( \mathrm{H}_{2} \mathrm{O} \), it rearranges to form acetaldehyde (\( \mathrm{CH}_{3} \mathrm{CHO} \)). Hence, the hydrolysis of 1,1-dichloroethane mainly yields acetaldehyde.

Step 5: Conclusion Step: Select the Correct Product

Thus, the correct answer to which compound is produced from the hydrolysis of \( \mathrm{CH}_{3} \mathrm{CHCl}_{2} \) is \( \mathrm{CH}_{3} \mathrm{CHO} \).

Key Concepts

1,1-dichloroethane

1,1-dichloroethane is an organohalide compound with the chemical formula \( \mathrm{CH}_{3} \mathrm{CHCl}_{2} \). This means it consists of an ethane backbone where two chlorine atoms are attached to a single carbon within the chain. This specific arrangement, where both chlorine atoms bond to the same carbon atom, defines it as a 1,1-disubstituted derivative of ethane.

• It is important to note that chlorine is highly electronegative. Its presence in the compound significantly affects the molecule's reactivity, making it prone to participate in reactions like hydrolysis.

When discussing 1,1-dichloroethane, it is often in the context of its reactivity due to the chlorine atoms. The presence of these halogen atoms makes it a potential candidate for various chemical transformations, which is why understanding its structure is crucial in predicting reactivity and products, especially in hydrolysis.

acetaldehyde

Acetaldehyde, with the chemical formula \( \mathrm{CH}_{3} \mathrm{CHO} \), is a key product you encounter in many hydrolysis reactions involving certain organohalides. It features a carbonyl group, where a carbon atom is double-bonded to an oxygen atom and single-bonded to a hydrogen and a methyl group.

• The formation of acetaldehyde from reactions like the hydrolysis of 1,1-dichloroethane is significant due to its position as an intermediary in various biological and industrial processes.

In the context of 1,1-dichloroethane hydrolysis, acetaldehyde forms from the initial unstable product, ethane-1,1-diol. This compound then loses water, given the term dehydration, to become acetaldehyde.

• The transformation demonstrates the common reaction pathway of converting unstable intermediates into more stable carbonyl-containing compounds.

organohalides

Organohalides are organic compounds where halogens (like chlorine, bromine, iodine, or fluorine) replace one or more hydrogen atoms in a hydrocarbon structure. In the case of 1,1-dichloroethane, chlorine is the halogen involved. These compounds are known for their distinct reactivity attributed to the electronegative halogen atoms.

• The presence of halogen atoms makes organohalides suitable for reactions like nucleophilic substitution and elimination, as well as hydrolysis.

Understanding the behavior of organohalides is crucial as they are widely used in industrial applications and synthetic organic chemistry. Their transformation and removal are often guided by the need to convert these potentially reactive intermediates into more benign or useful end products.

chemical reaction mechanism

The chemical reaction mechanism describes the step-by-step sequence in which reactants transform into products. It provides insight into how and why reactions occur, detailing intermediates, transition states, and energy changes involved. For the hydrolysis of 1,1-dichloroethane, understanding the mechanism helps clarify the transformation into acetaldehyde.

• The sequence starts with the nucleophilic attack of water on the carbon atom bonded to the chloro groups. This step replaces the chlorine atoms with hydroxyl groups.
• Following the substitution, the unstable ethane-1,1-diol intermediate is formed. This compound then undergoes a rearrangement, losing a water molecule to form a more stable acetaldehyde.

Each step involves shifts in electron pairs and bond formations or breakages, revealing the depths of the transformation process. A clear understanding of reaction mechanisms empowers students to predict and illustrate other potential reactions and outcomes for different compounds.