Isomerism: Overview, Questions, Preparation

First category of isomerism is the structural isomerism, which occurs due to difference in positioning of the atoms. These differences are given below for reference:

1. Chain Isomerism: This isomerism exists because of the variety in arrangement of carbon atoms in a chain such as straight or branched. For instance, butane $\left(C_4{H}_{10}\right)$ can be written both as n-butane (straight chain) and isobutane (branched chain). 
2. Position Isomerism: This isomerism occurs due to difference in the functional group's positioning in the carbon chain. For example, 1-propanol $\left({CH}_3{CH}_2{CH}_{2}OH\right)$ and 2-propanol ${(CH}_{3}CH\left(OH\right)C{H}_3)$ .
3. Functional Isomerism: Here, two different functional groups have same molecular formula's. For instance, ethanol ${(C}_2{H}_{5}OH)$ and dimethyl
   ether ${(CH}_{3}OC{H}_3)$  both have the formula $\left(C_2{H}_{6}O\right)$ , but one is an alcohol and the other an ether, leading to different chemical properties.

This is another type of isomerism where although the compounds have the same molecular formula, still they differ in the spatial arrangement of atoms. Further, it’s types include:

a) Geometrical Isomerism (cis/trans): This isomerism has different arrangements of the carbon atom around a circular orbit structure. It is observed in compounds with restricted rotation, typically around double bonds and rings. For example, but-2-ene ( ${\mathrm{C}\mathrm{H}}_3\mathrm{C}\mathrm{H}={\mathrm{C}\mathrm{H}\mathrm{C}\mathrm{H}}_3)$ .

b) Optical Isomerism: Occurs in compounds with a chiral center. These exist as non-superimposable mirror images that rotate plane-polarized light in different directions. Example, lactic acid $\left(C{H}_{3}CH\left(OH\right)COOH\right)$ .