Question

On monochlorination of 2 -methyl butane, the total number of chiral compounds is (a) 2 (b) 4 (c) 6 (d) 8

Short answer

The total number of chiral compounds is 2.

Step-by-step solution

Understand the Base Molecule

2-methylbutane is a branched alkane, consisting of a butane chain with a methyl group attached to the second carbon. The molecular structure can be written as C5H12.

Identify Possible Chlorination Sites

Chlorination replaces a hydrogen atom with a chlorine atom. In 2-methylbutane, chlorination can occur at any of the hydrogens on the carbon atoms of the structure.

Determine the Unique Products

Consider each carbon atom in the molecule as a possible site for monochlorination and determine if replacing a hydrogen at that site produces a unique product. The primary sites are C1, C2, C3, and C4, where C2 can also have hydrogens on the methyl group.

Evaluate Chirality for Each Product

A chiral center is a carbon atom attached to four different groups. Evaluate the products from monochlorination at each site to determine if they introduce a new chiral center in the molecule. C2 and C3 when chlorinated, create new chiral centers.

Count the Chiral Compounds

Identify how many of the unique monochlorinated products result in chiral molecules. From previous evaluation steps, chlorination at C2 and C3 specifically create chiral centers.

Key concepts

Monochlorination

Monochlorination is a chemical reaction where a single chlorine atom is substituted for a hydrogen atom in a molecule. This process is particularly important in organic chemistry as it leads to the creation of new compounds. In the case of 2-methylbutane, a branched alkane, monochlorination allows us to explore different sites for this substitution.
When considering monochlorination, it's important to note that each hydrogen atom in the 2-methylbutane molecule can potentially be replaced by chlorine. The outcome is dependent on the site of chlorination, often resulting in various isomers each with distinct properties. The strategy involves evaluating each potential site - in this context, the carbon atoms in 2-methylbutane - to determine where chlorination could occur, and how it affects the overall structure.

Chiral Centers

Chiral centers are pivotal in determining the properties and behaviors of organic molecules. A chiral center is typically a carbon atom bonded to four different groups, resulting in non-superimposable mirror images of molecules, known as enantiomers. These enantiomeric forms can have drastically different interactions and roles in chemical reactions and biological systems.
In 2-methylbutane, monochlorination can introduce new chiral centers, particularly when substitution occurs on C2 and C3. Evaluating each chlorinated product for chirality involves checking whether a chlorine substitution results in a carbon atom bonded to four distinct substituents. Understanding chiral centers is essential in predicting the possible outcomes of reactions and the potential for enantiomeric diversity following chlorination.

2-Methylbutane

2-Methylbutane, also known as isopentane, is a branched alkane with the molecular formula C5H12. This molecule consists of a four-carbon butane backbone with a methyl group attached to the second carbon, providing distinct structural considerations during chemical reactions.
Understanding its structure is crucial when investigating reactions like monochlorination. The branching significantly impacts the types of isomers that can form, as the methyl group creates asymmetry and unique sites for substitution. Recognizing these structural elements helps to predict the outcomes of chemical transformations, such as the introduction of new functional groups like chlorine in monochlorination studies.

Isomer Counting

Isomer counting involves identifying distinct chemical structures that arise from substituting an atom or group within a molecule, without altering the molecular formula. For organic compounds like 2-methylbutane, monochlorination can result in the formation of several isomers, depending on the position of the chlorine substitution.
Each potential site of chlorination - essentially, each carbon's hydrogen in the molecule - can yield a different isomer. The key to isomer counting is recognizing which positions, when substituted, lead to unique structural or spatial arrangements. In this case, determining the total number of chiral compounds involves counting these distinct arrangements that also possess a chiral center. Understanding isomer counting is fundamental for accurately predicting and categorizing the array of possible chemical byproducts from reactions like monochlorination.