Any tetrahedral atom with four different groups attached can be a chiral center. Which of these

Any tetrahedral atom with four different groups attached can...

Key Concepts

Optical Activity

Optical activity is the ability of chiral molecules to rotate the plane of polarized light. The existence of non-superimposable mirror images (enantiomers) means that a sample enriched in one enantiomer will interact with polarized light in a way that the other does not, a property that is critical for many applications in chemistry and pharmaceuticals.

Chirality

Chirality is the property of a molecule that makes it not superimposable on its mirror image. When a central atom is bonded to four different groups, it becomes a chiral centre, giving rise to two enantiomers that are mirror images of each other. This is a fundamental concept in stereochemistry, influencing the behavior and properties of molecules in many chemical and biological systems.

Tetrahedral Geometry

Tetrahedral geometry refers to a molecular shape where a central atom is surrounded by four substituents positioned at the corners of a tetrahedron. This arrangement, when the four attached groups are distinct, is the textbook case for chirality because it produces an asymmetrical, three?dimensional arrangement.

Inversion Barrier

The inversion barrier is the energy barrier that must be overcome for a molecule to invert its three-dimensional structure (such as the flipping seen in pyramidal molecules). For atoms like nitrogen, a low inversion barrier means rapid interconversion that often leads to an average (and hence achiral) structure, whereas a high inversion barrier in carbon, phosphorus, or heavier atoms helps maintain chirality.

Transcript

00:01 In this problem, we are given some of the species where the central atom has a tetrahedral arrangement.

00:10 We have to identify the species which are optically active.

00:15 First of all, we'll see what is an optically active substance.

00:19 Optical active compound is that compound which has a chiral center.

00:27 And chiral center means the atom which is bonded.

00:36 To four different substituents.

00:48 So in all these given species, we will see if the central atom is bonded to all the four different substituents, that will be considered optically active because of the presence of carol center.

00:59 Otherwise, the compound will be optically inactive.

01:02 So let's start with the first compound.

01:03 The first one is ch, c, h, c, lbrf.

01:08 If we draw the structure, we can have an arrangement where carbon is a central atom and it is bonded to hydrogen, chlorine, bromine, and fluorine.

01:22 And we can see central atom carbon is bonded to four different substituents.

01:29 So this compound is optically active.

01:39 Then we have the second compound where we have nbr, cl2h, and overall it has a positive charge, which is on the central atom.

01:49 Central atom here will be nitrogen.

01:51 And if we write the structure, we can write nitrogen, bonded to hydrogen this side, then wanted to chlorine this side, bromine, and bonded to chlorine this side also.

02:03 And there is a positive charge on nitrogen...

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