Question

The number of isomers for the compound with molecular formula \(\mathrm{C}_{2} \mathrm{BrClFI}\) is (a) 3 (b) 4 (c) 5 (d) 6

Short answer

The number of isomers is 4.

Step-by-step solution

Understand the Compound

A molecule with the formula \( \mathrm{C}_{2} \mathrm{BrClFI} \) consists of two carbon atoms and one of each of the substituent atoms: bromine (Br), chlorine (Cl), fluorine (F), and iodine (I). This is an example of a compound called a haloalkane.

Identify the Possible Structures

To determine the number of isomers, we should begin by considering the different configurations of the substituent atoms around the carbon atoms. Because there are four different substituents, each carbon atom can be a chiral center.

Calculate the Isomers

Each chiral carbon can have two configurations, R or S. Since there are two chiral centers, the maximum number of stereoisomers can be calculated as \(2^n\) where \(n\) is the number of chiral centers. Here \(n=2\), so the maximum number is \(2^2 = 4\).

Consider the Distinct Isomers

Since each configuration around each carbon is distinct due to the different substituents, each configuration contributes a unique isomer. Hence, all 4 configurations result in structurally distinct molecules. Therefore, there are 4 possible isomers.

Key concepts

Stereochemistry

Stereochemistry is a vital branch of chemistry that focuses on the three-dimensional arrangement of atoms within molecules. It helps in understanding how these spatial arrangements impact the physical and chemical properties of compounds. In the context of the exercise involving the compound \(\mathrm{C}_{2}\mathrm{BrClFI}\), stereochemistry plays a crucial role in identifying the different isomers that this molecule can form.

In molecules like \(\mathrm{C}_{2}\mathrm{BrClFI}\), where there are multiple atoms attached to carbon, understanding the different 3D configurations can reveal multiple isomers. These configurations are dependent on the spatial arrangement of the atoms, which could be very different even if the atoms involved are the same. Such variations lead to the formation of stereoisomers, each having a unique structure in physical space despite sharing the same molecular formula.

• Geometric isomers: These differ based on the position of atoms or groups around a double bond or ring structure.
• Optical isomers or enantiomers: These differ based on the ability to rotate polarized light due to the presence of chiral centers.

Understanding stereochemistry is essential for chemists as it influences everything from chemical reactivity to biological interactions.

Chiral Centers

A chiral center, often a carbon atom bonded to four different atoms or groups, is fundamental to understanding stereochemistry. This aspect of a molecule creates the possibility for it to exist in two non-superimposable mirror images called enantiomers. Each carbon in \(\mathrm{C}_{2}\mathrm{BrClFI}\) could potentially be a chiral center, offering different stereochemical configurations.

In simpler terms, chiral centers are the key to forming isomers in molecules. Due to the variety of substituents, each carbon atom can adopt a configuration known as either "R" (Rectus) or "S" (Sinister) based on the arrangement of substituents according to Cahn-Ingold-Prelog priority rules.

• "R" configuration: Determines the sequence via a clockwise priority of substituents.
• "S" configuration: Arranges the sequence counter-clockwise.

The presence of two chiral centers in the given compound means that there are \(2^2 = 4\) potential stereoisomers, each contributing to the compound's ability to form distinct spatial structures. Identifying and differentiating these configurations involve understanding chiral influences on chemical behaviors and interactions.

Haloalkanes

Haloalkanes are a type of aliphatic compound characterized by the replacement of one or more hydrogen atoms in an alkane with halogen atoms: fluorine, chlorine, bromine, or iodine. The compound \(\mathrm{C}_{2}\mathrm{BrClFI}\) is an example of a haloalkane because it includes these halogen atoms attached to its carbon backbone.

The presence of different halogens in haloalkanes can significantly influence their reactive properties. Each halogen varies in electronegativity and size, impacting the molecule's chemical behavior.

A few features of haloalkanes include:

• They are typically classified based on the number of neighboring carbons: primary, secondary, or tertiary.
• The halogen-carbon bonds make haloalkanes polar, affecting their boiling points and solubility.
• They often engage in substitution or elimination reactions, serving as starting points for creating more complex molecules.

The diversity in haloalkane structures due to various combinations of halogens results in many molecular isomers, each having unique properties and reactivities crucial for fields ranging from pharmaceuticals to organic synthesis.