Question

define chiral carbons
please elaborate them ​

Answer 1

Answer:

Explanation:

A chiral carbon or asymmetric carbon atom is a carbon atom that is attached to four different types of atoms or groups of atoms.

Le Bel-van't Hoff rule states that the number of stereoisomers of an organic compound is 2^n

, where n represents the number of asymmetric carbon atoms (unless there is an internal plane of symmetry); a corollary of Le Bel and van't Hoff's simultaneously announced conclusions, in 1874, that the most probable orientation of the bonds of a carbon atom linked to four groups or atoms is toward the apexes of a tetrahedron, and that this accounted for all then-known phenomena of molecular asymmetry (which involved a carbon atom bearing four different atoms or groups).

Knowing the number of asymmetric carbon atoms, one can calculate the maximum possible number of stereoisomers for any given molecule as follows:

If n is the number of asymmetric carbon atoms then the maximum number of isomers = 2^n

(Le Bel-van't Hoff rule)

As an example, malic acid has 4 carbon atoms but just one of them is asymmetric. The asymmetric carbon atom is the one attached to two carbon atoms, an oxygen atom, and a hydrogen atom. One may initially be inclined to think this atom is not asymmetric because it is attached to two carbon atoms, but because those two carbon atoms are not attached to exactly the same things, there are two different groups of atoms that the carbon atom in question is attached to, therefore making it an asymmetric carbon atom:

A tetrose with 2 asymmetric carbon atoms has 2^2

= 4 stereoisomers

An aldopentose with 3 asymmetric carbon atoms has 2^3

= 8 stereoisomers

An aldohexose with 4 asymmetric carbon atoms has 2^4

= 16 stereoisomers

The four groups of atoms attached to the carbon atom can be arranged in space in two different ways that are mirror images of each other, and which lead to so-called left-handed and versions of the same molecule. Molecules that cannot be superimposed on their own mirror image are said to be chiral.like mirror image.

Answer 2

The presence of a chiral carbon, or a chiral centre in a molecule is a condition for optical activity.

A carbon atom to which four different atoms or groups are attached is a chiral carbon.

All chiral centres are stereogenic centres, but not all stereogenic centres are chiral centres.

A chiral carbon must be sp³ hybridised, and attached to different groups.

Note that all sp³ carbons are not chiral.

For example, butane has no chiral carbon, but 2-chlorobutane has one chiral carbon.