Problem 179 - A Complete Resource Book in Chemistry for JEE Main

Question

Find the total number of monochlorinated products formed from the pure reactant given below : C=CC(C)C \(\left(*-{ }^{14} \mathrm{C}\right.\)-atom \()\)

Step-by-Step Solution

Answer

Four monochlorinated products are formed.

Step 1: Understand the Reactant Structure

The given reactant is isopentene, with a carbon structure represented as \( C=CC(C)C \). This can be visualized as three carbon atoms in a chain with a methyl group attached to the second carbon and a double bond between the first two carbons. Also, there is \( \textquoteleft *-{}^{14}\text{C}\textquoteleft \)-atom involved in monochlorination.

Step 2: Identify Monochlorination Sites

Monochlorination involves replacing one hydrogen atom in the reactant with a chlorine atom. In this structure, there are four unique carbon sites where the chlorine can attach. We need to evaluate each possible substitution location.

Step 3: Determining Unique Substitution Products

Substitution can occur at each of the four carbon atoms. The primary carbon (first) can form a unique product. The second carbon (which carries the methyl group) can form a unique product. The third carbon can form a unique product as it is linked to a different environment due to the adjacent methyl group. Lastly, substituting in the methyl group (fourth carbon) attached to the second carbon also gives a unique product. Overall, there are four unique carbon substitution points.

Step 4: Check Isomerism and Stability

We must check for potential isomerism or rearrangements. In this setup, each substitution forms distinct stereochemistry due to monosubstitution. Stability or rearrangement can affect final product count, but in this case, each substitution point is distinct without affecting others.

Key Concepts

Isopentene

Isopentene is a type of alkene, meaning it contains a carbon-carbon double bond. This feature is crucial as it makes isopentene reactive, allowing it to undergo different chemical reactions easily. The molecular structure of isopentene, represented by the SMILES notation, is:

• The chain comprises three carbon atoms.
• The double bond occurs between the first and second carbon.
• A methyl group is attached to the second carbon.

This makes isopentene look like: C=CC(C)C. Because it has a distinct geometry due to the double bond, it influences where chemical reactions can occur on the molecule. Understanding the basic structure of isopentene is important for predicting how it will react during substitution reactions like monochlorination.

Unique Substitution Products

When we talk about unique substitution products, we're discussing the different products formed when chlorine substitutes a hydrogen atom in a molecule. In isopentene, each carbon atom in the structure has a different chemical environment. This means, in the context of monochlorination, replacing a hydrogen on different carbon atoms will yield different products. Key points to consider include:

• The number of different environments, which determines the number of unique substitution products.
• Each carbon can potentially be a substitution site, but only those with different environments contribute to unique products.
• In isopentene's case, there are four unique sites: the primary carbon, the vinylic second carbon, the third carbon which links with the methyl group, and the carbon in the methyl group itself.

Thus, identifying unique substitution products involves distinguishing how similar or different each carbon's neighboring atoms are.

Organic Reaction Mechanisms

Organic reaction mechanisms are the step-by-step processes that describe how organic reactions occur. Understanding these is essential for predicting the outcomes of chemical reactions. In the context of monochlorination:

• A radical chlorination mechanism is usually involved.
• The reaction begins with the formation of chlorine radicals.
• These radicals substitute hydrogen atoms in the reactant, which happens stepwise, creating uniquely substituted products.

These mechanisms underline the importance of understanding reactivity, selectivity, and kinetics to anticipate where chlorine is likely to attach in isopentene.

Chemical Structure Analysis

Chemical structure analysis is about breaking down a molecule's structure to understand how it can react or transform. In analyzing the chemical structure of isopentene for monochlorination:

• First, visualize and mark each carbon atom's position and its attached hydrogen atoms.
• Identify the differences in each carbon's environment, which influences substitution reactions.
• Consider the stereochemistry, as how atoms are oriented can change reaction outcomes.

For isopentene, analyzing how the methyl group affects the third carbon, or how the double bond influences reactivity, reveals where monochlorination can form unique products. Engaging in detailed chemical structure analysis allows us to predict and verify the reaction paths and outcomes accurately.