Question

Relation between \(\mathrm{X}\) and \(\mathrm{Y}\) may be (A) Structural isomer (B) Stereoisomer (C) Identical (D) Non superimposable non-mirror images

Short answer

To determine the relationship between two molecules X and Y, examine their molecular formula, connectivity of their atoms, and orientation of their atoms in space. This analysis will help you identify if they are (A) structural isomers, (B) stereoisomers (either enantiomers or diastereomers), (C) identical molecules or (D) non-superimposable non-mirror images.

Step-by-step solution

Understanding Structural Isomers

Structural isomers are molecules that have the same molecular formula but different connectivity of their atoms. This means that they are composed of the same elements, but the arrangement of the atoms within the molecules is different.

Understanding Stereoisomers

Stereoisomers are molecules that have the same molecular formula and connectivity of their atoms, but differ in the orientation of these atoms in space. There are two types of stereoisomers: enantiomers and diastereomers. Enantiomers are mirror images of each other, while diastereomers are not.

Recognizing Identical Molecules

Identical molecules have the same molecular formula, connectivity of their atoms, and orientation of these atoms in space. In other words, they are exactly the same in every aspect.

Understanding Non-superimposable Non-mirror Images

Non-superimposable non-mirror images refer to molecules that are neither superimposable on each other nor are they mirror images. This generally means they are different molecules, and not isomers. It could arise, for example, when two molecules have a different set of functional groups, or in some cases, when they are constitutional isomers. As a result, to determine the relationship between two given molecules X and Y, we must carefully inspect their molecular formulas, the connectivity of their atoms, and the orientation of their atoms in space to decide if they are structural isomers, stereoisomers, identical molecules, or non-superimposable non-mirror images.

Key concepts

Structural Isomers

Structural isomers, also known as constitutional isomers, are fascinating because they have the same molecular formula but differ in the arrangement of atoms. This means that although the building blocks are identical, these blocks are connected differently in each molecule.
For example, consider the simplest alkanes such as butane ( propane) where carbons can join together in either a straight chain or a branched beginning.

• If you rearrange the carbon atoms to form a different backbone or change the position of functional groups, you form a structural isomer.
• This differing connectivity causes variations in the properties of the molecules, despite having the same amount and type of atoms.

To identify structural isomers, examine how atoms are bonded in the molecule and look for different possible connections. This can greatly affect the function and characteristics of the compounds in the chemical world.

Stereoisomers

Stereoisomers take molecular diversity to a different level. They have the same molecular formula and atom connectivity; however, they differ in three-dimensional space.
The most common stereoisomers include enantiomers and diastereomers, which literally turn the molecule's perspective upside down!

• Enantiomers are non-superimposable mirror images of each other.
• Diastereomers are also non-superimposable, but they are not mirror images.

The key to understanding stereoisomers is in their spatial arrangements. Small shifts in atom orientations lead to different interactions with other molecules and surroundings, ultimately affecting biological activity and physical properties.

Enantiomers

Enantiomers are a special type of stereoisomer that exist as mirror images but cannot be superimposed upon one another, much like a pair of hands. Their uniqueness arises from having chiral centers, which essentially act like locks where only the matching 'key' (this is the molecule) fits.
For instance, in biology, one enantiomer of a compound might be therapeutically active, whereas its mirror image can be inactive or even harmful.

• Their separation and identification are crucial, as they may rotate plane-polarized light differently, known as optical isomerism.
• When studying enantiomers, focus on chiral centers, which are atoms with four different groups attached.

Enantiomers are involved in numerous applications, such as pharmaceuticals, where the distinction between these optical twins can mean the difference between a cure and a poison.

Diastereomers

Diastereomers are fascinating because, unlike enantiomers, they are not mirror images and still, are non-superimposable. This class of stereoisomers arises when molecules have multiple chiral centers.
In contrast to enantiomers, diastereomers can have very different chemical and physical properties, including boiling points, solubilities, and reactivities.

• They occur when at least one of the stereo centers in a series changes its configuration.
• This difference allows diastereomers to be separated by ordinary chemical techniques, unlike enantiomers.

Recognizing diastereomers involves identifying multiple chiral centers and comparing their configurations. By studying these isomers, chemists can understand complexities in molecular structures and their resulting function.