Question

Types of stereoisomerism are optical isomerism and:
A. Cis-isomerism
B. Cis-trans isomerism
C. Trans-isomerism
D. All of these

Answer 1

Hint: Two or more compounds having the same molecular formula but different chemical and physical properties are called isomers and the phenomena are known as isomerism. It is of two types:
1. Structural isomerism
2. Stereo Isomerism

Complete step by step answer:
The phenomena in which the compounds have the same structural formula but different arrangements of atoms or groups in space are called stereoisomers and the compounds exhibiting this phenomena are known as stereoisomers. The word stereoisomers are of greek origin where stereo means space and meros means part. Stereoisomers are further classified as below.
1. Conformational isomers
2. Configurational isomers
Conformational isomers are defined as those stereoisomers which differ in the relative position of atoms within the molecule and which can be interconverted simply by rotation about the sigma bond. In conformational isomers, there is no breaking and remaking of a covalent bond whereas configurational isomers are defined as those stereoisomers which can be interconverted only by breaking and remaking of the covalent bond and not by simple rotation about the sigma bond. Configuration isomers are also two types:
1. Optical isomers
2. Geometrical isomers
Geometrical isomers are also known as cis-trans isomers. So we can say cis-trans isomers are also types of stereoisomers.

So, the correct answer is Option B.

Note: Geometrical isomers are defined as that configuration stereoisomer that has the same structural formula but differs in the spatial arrangements of atoms or groups around the double bond and the phenomena is known as geometrical isomerism. If in an isomer similar atom or group lies on the same side of double bond then it is called cis-isomer whereas if similar groups or atoms lie on a different side of double bond then it is called trans-isomers.