Question

How would you tell the difference between chiral and achiral structures?
For example:
1.${{H}_{3}}CCHBrC{{H}_{2}}C{{H}_{3}}$
2.$PC{{l}_{2}}BrC{{H}_{3}}^{+}$
3.$C{{l}_{3}}CCHFBr$
4.$HC$ triple bonded to $CC{{F}_{3}}$
5.$C{{H}_{2}}C{{l}_{3}}$
6.$HPClBrC{{H}_{3}}^{+}$
7.${{F}_{3}}CCB{{r}_{3}}$
8.${{H}_{3}}CBr$

Answer 1

Stereochemistry is defined as a systematic representation which deals with spatial arrangements of atoms and groups in a molecule. It is the branch of chemistry which includes study of three-dimensional arrangement of atoms.

Complete step-by-step answer: Stereochemistry focuses on stereo isomers which are defined as chemical compounds that have the same molecular formula but have different arrangement of atoms in three dimensions. Spatial arrangement of atoms means how different atomic particles are situated in the space around the organic compound. Chirality is defined as a property of an object that is asymmetric and cannot be superimposed on mirror images. Chiral center is defined as an atom that consists of four different groups attached to an atom and cannot be superimposed over mirror images.
Chiral compounds are non-superimposable mirror images of each other, whereas achiral is superimposable over their mirror images.
A compound is said to be a chiral compound when it does not have a plane of symmetry and center of symmetry. If a compound does not consist of any of these, then it is termed as chiral compound.
Plane of symmetry is defined as a plane that divides a molecule into two equal halves. It shows a mirror image of each other.
Center of symmetry is defined as a point that shows equal distance when we move towards two equivalent groups. If a compound shows either plane of symmetry or center of symmetry, then it is said to be an achiral compound, and if a compound does not show anyone of them, then it is said to be a chiral compound.
Let us see the given examples one by one.
1.${{H}_{3}}C\overset{*}{\mathop{C}}\,HBrC{{H}_{2}}C{{H}_{3}}$ : This compound is a chiral compound because it does not show plane of symmetry and center of symmetry. And it contains all different substituents.
2.$PC{{l}_{2}}BrC{{H}_{3}}^{+}$ : This compound is achiral. Phosphorus is the central atom. This compound is achiral because all four different substituents are not attached to the central atom. Here, two chlorine substituents are present.
3.$C{{l}_{3}}C\overset{*}{\mathop{C}}\,HFBr$ : This is a chiral compound as all four different substituents are attached to the central atom
4.$HC\equiv CC{{F}_{3}}$ : This compound is achiral because it contains only two groups.
5.$C{{H}_{2}}C{{l}_{3}}$ : No such type of molecule exists in organic chemistry.
6.$HPClBrC{{H}_{3}}^{+}$ : This is a chiral compound because it contains all different four groups. Here, phosphorus is the central atom.
7.${{F}_{3}}CCB{{r}_{3}}$ : This compound is achiral because all four different groups are not attached.
8.${{H}_{3}}CBr$ : This compound is achiral because all different groups are not attached and three atoms of hydrogen are present.

Note: It is to be noted that chiral compounds do not show superimposable mirror images and achiral compounds do show superimposable mirror images of each other. In conclusion, if a compound contains four different substituents attached to the central atom, then that compound is said to be chiral compound.