Question

Which of the following compounds is optically inactive?
A. 3-Chloro-but-1-ene
B. 2,3- Dichlorobutane
C. 2- Hydroxy propanoic acid
D. 2,2 - Dichloro pentane

Answer 1

Hint: Two kinds of molecules are found i.e. chiral and achiral molecules. The optical property of a molecule depends on the type chirality and achirality of the molecule. The carbon which makes the bond with four different molecules is known as chiral carbon.

Complete Step-by-Step Answer:
-Firstly, we have to identify the chiral and achiral molecule from the given molecules.
-As we know that chiral molecules are those molecules whose mirror images do not superimpose on each other and also they are not symmetrical molecules.
-The molecules also show the optical property because it is observed that when a light beam is passed through the molecule then it starts to rotate in a particular direction.
-There are two directions in which they can move that are clockwise or dextrorotatory and anticlockwise or levorotatory.
-Whereas when a light beam is passed through the achiral molecules then it doesn't rotate in any direction due to which it is considered as an optically inactive molecule.
-So, we have to observe the achiral molecule that is:

-Above given diagrams is the structure of the molecules given in the question.
-As we can see that all the molecules consist of chiral carbon except 2,2- Dichloro pentane.
-So, we can say that 2,2- Dichloro pentane is achiral molecule due to which it is optically inactive and their mirror image is also superimposable on each other i.e.

Therefore, option D is the correct answer.

Note: The chiral carbon is also represented by the asterisk ($*$). Racemization is the process in which the optically active solution is converted into the optically inactive solution by the conversion of either leavo into dextro or dextro into leavo direction.